[SPARK-13583][CORE][STREAMING] Remove unused imports and add checkstyle rule

## What changes were proposed in this pull request?

After SPARK-6990, `dev/lint-java` keeps Java code healthy and helps PR review by saving much time.
This issue aims remove unused imports from Java/Scala code and add `UnusedImports` checkstyle rule to help developers.

## How was this patch tested?
```
./dev/lint-java
./build/sbt compile
```

Author: Dongjoon Hyun <dongjoon@apache.org>

Closes #11438 from dongjoon-hyun/SPARK-13583.

226 files changed, 103 insertions, 337 deletions

diff --git a/checkstyle.xml b/checkstyle.xml
index b5d1617ba4..a165fee2a4 100644
--- a/checkstyle.xml
+++ b/checkstyle.xml
@@ -166,5 +166,6 @@
             <property name="exceptionVariableName" value="expected"/>
         </module>
         <module name="CommentsIndentation"/>
+        <module name="UnusedImports"/>
     </module>
 </module>
diff --git a/common/network-common/src/main/java/org/apache/spark/network/protocol/OneWayMessage.java b/common/network-common/src/main/java/org/apache/spark/network/protocol/OneWayMessage.java
index efe0470f35..f7ffb1bd49 100644
--- a/common/network-common/src/main/java/org/apache/spark/network/protocol/OneWayMessage.java
+++ b/common/network-common/src/main/java/org/apache/spark/network/protocol/OneWayMessage.java
@@ -19,7 +19,6 @@ package org.apache.spark.network.protocol;
 
 import com.google.common.base.Objects;
 import io.netty.buffer.ByteBuf;
-import io.netty.buffer.Unpooled;
 
 import org.apache.spark.network.buffer.ManagedBuffer;
 import org.apache.spark.network.buffer.NettyManagedBuffer;
diff --git a/common/network-common/src/main/java/org/apache/spark/network/protocol/RpcRequest.java b/common/network-common/src/main/java/org/apache/spark/network/protocol/RpcRequest.java
index 96213794a8..2b30920f05 100644
--- a/common/network-common/src/main/java/org/apache/spark/network/protocol/RpcRequest.java
+++ b/common/network-common/src/main/java/org/apache/spark/network/protocol/RpcRequest.java
@@ -19,7 +19,6 @@ package org.apache.spark.network.protocol;
 
 import com.google.common.base.Objects;
 import io.netty.buffer.ByteBuf;
-import io.netty.buffer.Unpooled;
 
 import org.apache.spark.network.buffer.ManagedBuffer;
 import org.apache.spark.network.buffer.NettyManagedBuffer;
diff --git a/common/network-common/src/main/java/org/apache/spark/network/protocol/RpcResponse.java b/common/network-common/src/main/java/org/apache/spark/network/protocol/RpcResponse.java
index bae866e14a..d73014ecd8 100644
--- a/common/network-common/src/main/java/org/apache/spark/network/protocol/RpcResponse.java
+++ b/common/network-common/src/main/java/org/apache/spark/network/protocol/RpcResponse.java
@@ -19,7 +19,6 @@ package org.apache.spark.network.protocol;
 
 import com.google.common.base.Objects;
 import io.netty.buffer.ByteBuf;
-import io.netty.buffer.Unpooled;
 
 import org.apache.spark.network.buffer.ManagedBuffer;
 import org.apache.spark.network.buffer.NettyManagedBuffer;
diff --git a/common/network-common/src/main/java/org/apache/spark/network/protocol/StreamFailure.java b/common/network-common/src/main/java/org/apache/spark/network/protocol/StreamFailure.java
index 26747ee55b..258ef81c67 100644
--- a/common/network-common/src/main/java/org/apache/spark/network/protocol/StreamFailure.java
+++ b/common/network-common/src/main/java/org/apache/spark/network/protocol/StreamFailure.java
@@ -20,9 +20,6 @@ package org.apache.spark.network.protocol;
 import com.google.common.base.Objects;
 import io.netty.buffer.ByteBuf;
 
-import org.apache.spark.network.buffer.ManagedBuffer;
-import org.apache.spark.network.buffer.NettyManagedBuffer;
-
 /**
  * Message indicating an error when transferring a stream.
  */
diff --git a/common/network-common/src/main/java/org/apache/spark/network/protocol/StreamRequest.java b/common/network-common/src/main/java/org/apache/spark/network/protocol/StreamRequest.java
index 35af5a84ba..dc183c043e 100644
--- a/common/network-common/src/main/java/org/apache/spark/network/protocol/StreamRequest.java
+++ b/common/network-common/src/main/java/org/apache/spark/network/protocol/StreamRequest.java
@@ -20,9 +20,6 @@ package org.apache.spark.network.protocol;
 import com.google.common.base.Objects;
 import io.netty.buffer.ByteBuf;
 
-import org.apache.spark.network.buffer.ManagedBuffer;
-import org.apache.spark.network.buffer.NettyManagedBuffer;
-
 /**
  * Request to stream data from the remote end.
  * <p>
diff --git a/common/network-common/src/main/java/org/apache/spark/network/protocol/StreamResponse.java b/common/network-common/src/main/java/org/apache/spark/network/protocol/StreamResponse.java
index 51b899930f..87e212f3e1 100644
--- a/common/network-common/src/main/java/org/apache/spark/network/protocol/StreamResponse.java
+++ b/common/network-common/src/main/java/org/apache/spark/network/protocol/StreamResponse.java
@@ -21,7 +21,6 @@ import com.google.common.base.Objects;
 import io.netty.buffer.ByteBuf;
 
 import org.apache.spark.network.buffer.ManagedBuffer;
-import org.apache.spark.network.buffer.NettyManagedBuffer;
 
 /**
  * Response to {@link StreamRequest} when the stream has been successfully opened.
diff --git a/common/network-common/src/main/java/org/apache/spark/network/sasl/SaslEncryption.java b/common/network-common/src/main/java/org/apache/spark/network/sasl/SaslEncryption.java
index 127335e4d3..3d71ebaa7e 100644
--- a/common/network-common/src/main/java/org/apache/spark/network/sasl/SaslEncryption.java
+++ b/common/network-common/src/main/java/org/apache/spark/network/sasl/SaslEncryption.java
@@ -33,7 +33,6 @@ import io.netty.channel.ChannelPromise;
 import io.netty.channel.FileRegion;
 import io.netty.handler.codec.MessageToMessageDecoder;
 import io.netty.util.AbstractReferenceCounted;
-import io.netty.util.ReferenceCountUtil;
 
 import org.apache.spark.network.util.ByteArrayWritableChannel;
 import org.apache.spark.network.util.NettyUtils;
diff --git a/common/network-common/src/main/java/org/apache/spark/network/server/TransportRequestHandler.java b/common/network-common/src/main/java/org/apache/spark/network/server/TransportRequestHandler.java
index 296ced3db0..bebe88ec5d 100644
--- a/common/network-common/src/main/java/org/apache/spark/network/server/TransportRequestHandler.java
+++ b/common/network-common/src/main/java/org/apache/spark/network/server/TransportRequestHandler.java
@@ -19,7 +19,6 @@ package org.apache.spark.network.server;
 
 import java.nio.ByteBuffer;
 
-import com.google.common.base.Preconditions;
 import com.google.common.base.Throwables;
 import io.netty.channel.Channel;
 import io.netty.channel.ChannelFuture;
diff --git a/common/network-common/src/main/java/org/apache/spark/network/util/NettyUtils.java b/common/network-common/src/main/java/org/apache/spark/network/util/NettyUtils.java
index caa7260bc8..10de9d3a5c 100644
--- a/common/network-common/src/main/java/org/apache/spark/network/util/NettyUtils.java
+++ b/common/network-common/src/main/java/org/apache/spark/network/util/NettyUtils.java
@@ -31,8 +31,6 @@ import io.netty.channel.epoll.EpollSocketChannel;
 import io.netty.channel.nio.NioEventLoopGroup;
 import io.netty.channel.socket.nio.NioServerSocketChannel;
 import io.netty.channel.socket.nio.NioSocketChannel;
-import io.netty.handler.codec.ByteToMessageDecoder;
-import io.netty.handler.codec.LengthFieldBasedFrameDecoder;
 import io.netty.util.internal.PlatformDependent;
 
 /**
diff --git a/common/network-common/src/main/java/org/apache/spark/network/util/TransportFrameDecoder.java b/common/network-common/src/main/java/org/apache/spark/network/util/TransportFrameDecoder.java
index a466c72915..3f7024a6aa 100644
--- a/common/network-common/src/main/java/org/apache/spark/network/util/TransportFrameDecoder.java
+++ b/common/network-common/src/main/java/org/apache/spark/network/util/TransportFrameDecoder.java
@@ -17,7 +17,6 @@
 
 package org.apache.spark.network.util;
 
-import java.util.Iterator;
 import java.util.LinkedList;
 
 import com.google.common.base.Preconditions;
diff --git a/common/network-shuffle/src/main/java/org/apache/spark/network/sasl/ShuffleSecretManager.java b/common/network-shuffle/src/main/java/org/apache/spark/network/sasl/ShuffleSecretManager.java
index 351c7930a9..cdce297233 100644
--- a/common/network-shuffle/src/main/java/org/apache/spark/network/sasl/ShuffleSecretManager.java
+++ b/common/network-shuffle/src/main/java/org/apache/spark/network/sasl/ShuffleSecretManager.java
@@ -24,7 +24,6 @@ import java.util.concurrent.ConcurrentHashMap;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import org.apache.spark.network.sasl.SecretKeyHolder;
 import org.apache.spark.network.util.JavaUtils;
 
 /**
diff --git a/common/network-shuffle/src/test/java/org/apache/spark/network/shuffle/ExternalShuffleSecuritySuite.java b/common/network-shuffle/src/test/java/org/apache/spark/network/shuffle/ExternalShuffleSecuritySuite.java
index 08ddb3755b..acc1168f83 100644
--- a/common/network-shuffle/src/test/java/org/apache/spark/network/shuffle/ExternalShuffleSecuritySuite.java
+++ b/common/network-shuffle/src/test/java/org/apache/spark/network/shuffle/ExternalShuffleSecuritySuite.java
@@ -30,7 +30,6 @@ import org.apache.spark.network.TestUtils;
 import org.apache.spark.network.TransportContext;
 import org.apache.spark.network.sasl.SaslServerBootstrap;
 import org.apache.spark.network.sasl.SecretKeyHolder;
-import org.apache.spark.network.server.RpcHandler;
 import org.apache.spark.network.server.TransportServer;
 import org.apache.spark.network.server.TransportServerBootstrap;
 import org.apache.spark.network.shuffle.protocol.ExecutorShuffleInfo;
diff --git a/core/src/main/java/org/apache/spark/shuffle/sort/PackedRecordPointer.java b/core/src/main/java/org/apache/spark/shuffle/sort/PackedRecordPointer.java
index f8f2b220e1..f7a6c68be9 100644
--- a/core/src/main/java/org/apache/spark/shuffle/sort/PackedRecordPointer.java
+++ b/core/src/main/java/org/apache/spark/shuffle/sort/PackedRecordPointer.java
@@ -17,8 +17,6 @@
 
 package org.apache.spark.shuffle.sort;
 
-import org.apache.spark.memory.TaskMemoryManager;
-
 /**
  * Wrapper around an 8-byte word that holds a 24-bit partition number and 40-bit record pointer.
  * <p>
@@ -28,7 +26,7 @@ import org.apache.spark.memory.TaskMemoryManager;
  * </pre>
  * This implies that the maximum addressable page size is 2^27 bits = 128 megabytes, assuming that
  * our offsets in pages are not 8-byte-word-aligned. Since we have 2^13 pages (based off the
- * 13-bit page numbers assigned by {@link TaskMemoryManager}), this
+ * 13-bit page numbers assigned by {@link org.apache.spark.memory.TaskMemoryManager}), this
  * implies that we can address 2^13 * 128 megabytes = 1 terabyte of RAM per task.
  * <p>
  * Assuming word-alignment would allow for a 1 gigabyte maximum page size, but we leave this
diff --git a/core/src/main/java/org/apache/spark/shuffle/sort/UnsafeShuffleWriter.java b/core/src/main/java/org/apache/spark/shuffle/sort/UnsafeShuffleWriter.java
index 128a82579b..3f4402bd3a 100644
--- a/core/src/main/java/org/apache/spark/shuffle/sort/UnsafeShuffleWriter.java
+++ b/core/src/main/java/org/apache/spark/shuffle/sort/UnsafeShuffleWriter.java
@@ -25,7 +25,6 @@ import java.util.Iterator;
 import scala.Option;
 import scala.Product2;
 import scala.collection.JavaConverters;
-import scala.collection.immutable.Map;
 import scala.reflect.ClassTag;
 import scala.reflect.ClassTag$;
 
diff --git a/core/src/main/java/org/apache/spark/util/collection/unsafe/sort/PrefixComparators.java b/core/src/main/java/org/apache/spark/util/collection/unsafe/sort/PrefixComparators.java
index d2bf297c6c..c2a8f429be 100644
--- a/core/src/main/java/org/apache/spark/util/collection/unsafe/sort/PrefixComparators.java
+++ b/core/src/main/java/org/apache/spark/util/collection/unsafe/sort/PrefixComparators.java
@@ -20,7 +20,6 @@ package org.apache.spark.util.collection.unsafe.sort;
 import com.google.common.primitives.UnsignedLongs;
 
 import org.apache.spark.annotation.Private;
-import org.apache.spark.unsafe.Platform;
 import org.apache.spark.unsafe.types.ByteArray;
 import org.apache.spark.unsafe.types.UTF8String;
 import org.apache.spark.util.Utils;
diff --git a/core/src/main/java/org/apache/spark/util/collection/unsafe/sort/RecordPointerAndKeyPrefix.java b/core/src/main/java/org/apache/spark/util/collection/unsafe/sort/RecordPointerAndKeyPrefix.java
index dbf6770e07..de92b8db47 100644
--- a/core/src/main/java/org/apache/spark/util/collection/unsafe/sort/RecordPointerAndKeyPrefix.java
+++ b/core/src/main/java/org/apache/spark/util/collection/unsafe/sort/RecordPointerAndKeyPrefix.java
@@ -17,11 +17,9 @@
 
 package org.apache.spark.util.collection.unsafe.sort;
 
-import org.apache.spark.memory.TaskMemoryManager;
-
 final class RecordPointerAndKeyPrefix {
   /**
-   * A pointer to a record; see {@link TaskMemoryManager} for a
+   * A pointer to a record; see {@link org.apache.spark.memory.TaskMemoryManager} for a
    * description of how these addresses are encoded.
    */
   public long recordPointer;
diff --git a/core/src/main/scala/org/apache/spark/ExecutorAllocationManager.scala b/core/src/main/scala/org/apache/spark/ExecutorAllocationManager.scala
index db143d7341..9b8279f43e 100644
--- a/core/src/main/scala/org/apache/spark/ExecutorAllocationManager.scala
+++ b/core/src/main/scala/org/apache/spark/ExecutorAllocationManager.scala
@@ -26,7 +26,7 @@ import com.codahale.metrics.{Gauge, MetricRegistry}
 
 import org.apache.spark.metrics.source.Source
 import org.apache.spark.scheduler._
-import org.apache.spark.util.{Clock, SystemClock, ThreadUtils, Utils}
+import org.apache.spark.util.{Clock, SystemClock, ThreadUtils}
 
 /**
  * An agent that dynamically allocates and removes executors based on the workload.
diff --git a/core/src/main/scala/org/apache/spark/HeartbeatReceiver.scala b/core/src/main/scala/org/apache/spark/HeartbeatReceiver.scala
index 45b20c0e8d..7f474ed591 100644
--- a/core/src/main/scala/org/apache/spark/HeartbeatReceiver.scala
+++ b/core/src/main/scala/org/apache/spark/HeartbeatReceiver.scala
@@ -22,7 +22,6 @@ import java.util.concurrent.{ScheduledFuture, TimeUnit}
 import scala.collection.mutable
 import scala.concurrent.Future
 
-import org.apache.spark.executor.TaskMetrics
 import org.apache.spark.rpc.{RpcCallContext, RpcEnv, ThreadSafeRpcEndpoint}
 import org.apache.spark.scheduler._
 import org.apache.spark.storage.BlockManagerId
diff --git a/core/src/main/scala/org/apache/spark/Partitioner.scala b/core/src/main/scala/org/apache/spark/Partitioner.scala
index 976c19f2b0..98c3abe93b 100644
--- a/core/src/main/scala/org/apache/spark/Partitioner.scala
+++ b/core/src/main/scala/org/apache/spark/Partitioner.scala
@@ -21,13 +21,13 @@ import java.io.{IOException, ObjectInputStream, ObjectOutputStream}
 
 import scala.collection.mutable
 import scala.collection.mutable.ArrayBuffer
-import scala.reflect.{classTag, ClassTag}
+import scala.reflect.ClassTag
 import scala.util.hashing.byteswap32
 
 import org.apache.spark.rdd.{PartitionPruningRDD, RDD}
 import org.apache.spark.serializer.JavaSerializer
 import org.apache.spark.util.{CollectionsUtils, Utils}
-import org.apache.spark.util.random.{SamplingUtils, XORShiftRandom}
+import org.apache.spark.util.random.SamplingUtils
 
 /**
  * An object that defines how the elements in a key-value pair RDD are partitioned by key.
diff --git a/core/src/main/scala/org/apache/spark/SparkContext.scala b/core/src/main/scala/org/apache/spark/SparkContext.scala
index b503c6184a..9f5a72bae0 100644
--- a/core/src/main/scala/org/apache/spark/SparkContext.scala
+++ b/core/src/main/scala/org/apache/spark/SparkContext.scala
@@ -51,7 +51,6 @@ import org.apache.spark.deploy.{LocalSparkCluster, SparkHadoopUtil}
 import org.apache.spark.input.{FixedLengthBinaryInputFormat, PortableDataStream, StreamInputFormat,
   WholeTextFileInputFormat}
 import org.apache.spark.io.CompressionCodec
-import org.apache.spark.metrics.MetricsSystem
 import org.apache.spark.partial.{ApproximateEvaluator, PartialResult}
 import org.apache.spark.rdd._
 import org.apache.spark.rpc.RpcEndpointRef
diff --git a/core/src/main/scala/org/apache/spark/TaskNotSerializableException.scala b/core/src/main/scala/org/apache/spark/TaskNotSerializableException.scala
index 9df61062e1..0cb93f131a 100644
--- a/core/src/main/scala/org/apache/spark/TaskNotSerializableException.scala
+++ b/core/src/main/scala/org/apache/spark/TaskNotSerializableException.scala
@@ -17,8 +17,6 @@
 
 package org.apache.spark
 
-import org.apache.spark.annotation.DeveloperApi
-
 /**
  * Exception thrown when a task cannot be serialized.
  */
diff --git a/core/src/main/scala/org/apache/spark/api/java/JavaRDD.scala b/core/src/main/scala/org/apache/spark/api/java/JavaRDD.scala
index ed312770ee..20d6c9341b 100644
--- a/core/src/main/scala/org/apache/spark/api/java/JavaRDD.scala
+++ b/core/src/main/scala/org/apache/spark/api/java/JavaRDD.scala
@@ -17,8 +17,6 @@
 
 package org.apache.spark.api.java
 
-import java.util.Comparator
-
 import scala.language.implicitConversions
 import scala.reflect.ClassTag
 
@@ -191,7 +189,6 @@ class JavaRDD[T](val rdd: RDD[T])(implicit val classTag: ClassTag[T])
    * Return this RDD sorted by the given key function.
    */
   def sortBy[S](f: JFunction[T, S], ascending: Boolean, numPartitions: Int): JavaRDD[T] = {
-    import scala.collection.JavaConverters._
     def fn: (T) => S = (x: T) => f.call(x)
     import com.google.common.collect.Ordering  // shadows scala.math.Ordering
     implicit val ordering = Ordering.natural().asInstanceOf[Ordering[S]]
diff --git a/core/src/main/scala/org/apache/spark/broadcast/BroadcastFactory.scala b/core/src/main/scala/org/apache/spark/broadcast/BroadcastFactory.scala
index 7f35ac4747..fd7b4fc88b 100644
--- a/core/src/main/scala/org/apache/spark/broadcast/BroadcastFactory.scala
+++ b/core/src/main/scala/org/apache/spark/broadcast/BroadcastFactory.scala
@@ -21,7 +21,6 @@ import scala.reflect.ClassTag
 
 import org.apache.spark.SecurityManager
 import org.apache.spark.SparkConf
-import org.apache.spark.annotation.DeveloperApi
 
 /**
  * An interface for all the broadcast implementations in Spark (to allow
diff --git a/core/src/main/scala/org/apache/spark/deploy/RPackageUtils.scala b/core/src/main/scala/org/apache/spark/deploy/RPackageUtils.scala
index 4911c3be3a..81718e0c44 100644
--- a/core/src/main/scala/org/apache/spark/deploy/RPackageUtils.scala
+++ b/core/src/main/scala/org/apache/spark/deploy/RPackageUtils.scala
@@ -26,7 +26,7 @@ import scala.collection.JavaConverters._
 
 import com.google.common.io.{ByteStreams, Files}
 
-import org.apache.spark.{Logging, SparkException}
+import org.apache.spark.Logging
 import org.apache.spark.api.r.RUtils
 import org.apache.spark.util.{RedirectThread, Utils}
 
diff --git a/core/src/main/scala/org/apache/spark/deploy/master/DriverInfo.scala b/core/src/main/scala/org/apache/spark/deploy/master/DriverInfo.scala
index b197dbcbfe..8d5edae050 100644
--- a/core/src/main/scala/org/apache/spark/deploy/master/DriverInfo.scala
+++ b/core/src/main/scala/org/apache/spark/deploy/master/DriverInfo.scala
@@ -19,7 +19,6 @@ package org.apache.spark.deploy.master
 
 import java.util.Date
 
-import org.apache.spark.annotation.DeveloperApi
 import org.apache.spark.deploy.DriverDescription
 import org.apache.spark.util.Utils
 
diff --git a/core/src/main/scala/org/apache/spark/deploy/worker/Worker.scala b/core/src/main/scala/org/apache/spark/deploy/worker/Worker.scala
index 1c24c631ee..283db6c4fe 100755
--- a/core/src/main/scala/org/apache/spark/deploy/worker/Worker.scala
+++ b/core/src/main/scala/org/apache/spark/deploy/worker/Worker.scala
@@ -37,7 +37,7 @@ import org.apache.spark.deploy.master.{DriverState, Master}
 import org.apache.spark.deploy.worker.ui.WorkerWebUI
 import org.apache.spark.metrics.MetricsSystem
 import org.apache.spark.rpc._
-import org.apache.spark.util.{SignalLogger, ThreadUtils, Utils}
+import org.apache.spark.util.{ThreadUtils, Utils}
 
 private[deploy] class Worker(
     override val rpcEnv: RpcEnv,
diff --git a/core/src/main/scala/org/apache/spark/deploy/worker/ui/LogPage.scala b/core/src/main/scala/org/apache/spark/deploy/worker/ui/LogPage.scala
index 0ca90640ae..09ae64af8a 100644
--- a/core/src/main/scala/org/apache/spark/deploy/worker/ui/LogPage.scala
+++ b/core/src/main/scala/org/apache/spark/deploy/worker/ui/LogPage.scala
@@ -18,7 +18,6 @@
 package org.apache.spark.deploy.worker.ui
 
 import java.io.File
-import java.net.URI
 import javax.servlet.http.HttpServletRequest
 
 import scala.xml.Node
diff --git a/core/src/main/scala/org/apache/spark/rdd/DoubleRDDFunctions.scala b/core/src/main/scala/org/apache/spark/rdd/DoubleRDDFunctions.scala
index bd61d04d42..c9606600ed 100644
--- a/core/src/main/scala/org/apache/spark/rdd/DoubleRDDFunctions.scala
+++ b/core/src/main/scala/org/apache/spark/rdd/DoubleRDDFunctions.scala
@@ -18,7 +18,6 @@
 package org.apache.spark.rdd
 
 import org.apache.spark.{Logging, TaskContext}
-import org.apache.spark.annotation.Experimental
 import org.apache.spark.partial.BoundedDouble
 import org.apache.spark.partial.MeanEvaluator
 import org.apache.spark.partial.PartialResult
diff --git a/core/src/main/scala/org/apache/spark/rdd/JdbcRDD.scala b/core/src/main/scala/org/apache/spark/rdd/JdbcRDD.scala
index 469962db67..8cbe80d650 100644
--- a/core/src/main/scala/org/apache/spark/rdd/JdbcRDD.scala
+++ b/core/src/main/scala/org/apache/spark/rdd/JdbcRDD.scala
@@ -17,7 +17,7 @@
 
 package org.apache.spark.rdd
 
-import java.sql.{Connection, PreparedStatement, ResultSet}
+import java.sql.{Connection, ResultSet}
 
 import scala.reflect.ClassTag
 
diff --git a/core/src/main/scala/org/apache/spark/rdd/LocalCheckpointRDD.scala b/core/src/main/scala/org/apache/spark/rdd/LocalCheckpointRDD.scala
index a163bbd264..503aa0dffc 100644
--- a/core/src/main/scala/org/apache/spark/rdd/LocalCheckpointRDD.scala
+++ b/core/src/main/scala/org/apache/spark/rdd/LocalCheckpointRDD.scala
@@ -19,7 +19,7 @@ package org.apache.spark.rdd
 
 import scala.reflect.ClassTag
 
-import org.apache.spark.{Partition, SparkContext, SparkEnv, SparkException, TaskContext}
+import org.apache.spark.{Partition, SparkContext, SparkException, TaskContext}
 import org.apache.spark.storage.RDDBlockId
 
 /**
diff --git a/core/src/main/scala/org/apache/spark/rdd/ReliableRDDCheckpointData.scala b/core/src/main/scala/org/apache/spark/rdd/ReliableRDDCheckpointData.scala
index cac6cbe780..92f625f755 100644
--- a/core/src/main/scala/org/apache/spark/rdd/ReliableRDDCheckpointData.scala
+++ b/core/src/main/scala/org/apache/spark/rdd/ReliableRDDCheckpointData.scala
@@ -22,7 +22,6 @@ import scala.reflect.ClassTag
 import org.apache.hadoop.fs.Path
 
 import org.apache.spark._
-import org.apache.spark.util.SerializableConfiguration
 
 /**
  * An implementation of checkpointing that writes the RDD data to reliable storage.
diff --git a/core/src/main/scala/org/apache/spark/rpc/netty/NettyRpcEnv.scala b/core/src/main/scala/org/apache/spark/rpc/netty/NettyRpcEnv.scala
index 89eda857e6..c83a632e43 100644
--- a/core/src/main/scala/org/apache/spark/rpc/netty/NettyRpcEnv.scala
+++ b/core/src/main/scala/org/apache/spark/rpc/netty/NettyRpcEnv.scala
@@ -17,7 +17,6 @@
 package org.apache.spark.rpc.netty
 
 import java.io._
-import java.lang.{Boolean => JBoolean}
 import java.net.{InetSocketAddress, URI}
 import java.nio.ByteBuffer
 import java.nio.channels.{Pipe, ReadableByteChannel, WritableByteChannel}
diff --git a/core/src/main/scala/org/apache/spark/scheduler/ActiveJob.scala b/core/src/main/scala/org/apache/spark/scheduler/ActiveJob.scala
index a3d2db3130..949e88f606 100644
--- a/core/src/main/scala/org/apache/spark/scheduler/ActiveJob.scala
+++ b/core/src/main/scala/org/apache/spark/scheduler/ActiveJob.scala
@@ -19,7 +19,6 @@ package org.apache.spark.scheduler
 
 import java.util.Properties
 
-import org.apache.spark.TaskContext
 import org.apache.spark.util.CallSite
 
 /**
diff --git a/core/src/main/scala/org/apache/spark/scheduler/DAGSchedulerEvent.scala b/core/src/main/scala/org/apache/spark/scheduler/DAGSchedulerEvent.scala
index d5cd2da7a1..a3845c6acd 100644
--- a/core/src/main/scala/org/apache/spark/scheduler/DAGSchedulerEvent.scala
+++ b/core/src/main/scala/org/apache/spark/scheduler/DAGSchedulerEvent.scala
@@ -19,11 +19,9 @@ package org.apache.spark.scheduler
 
 import java.util.Properties
 
-import scala.collection.Map
 import scala.language.existentials
 
 import org.apache.spark._
-import org.apache.spark.executor.TaskMetrics
 import org.apache.spark.rdd.RDD
 import org.apache.spark.util.CallSite
 
diff --git a/core/src/main/scala/org/apache/spark/scheduler/TaskScheduler.scala b/core/src/main/scala/org/apache/spark/scheduler/TaskScheduler.scala
index fccd6e0699..8477a66b39 100644
--- a/core/src/main/scala/org/apache/spark/scheduler/TaskScheduler.scala
+++ b/core/src/main/scala/org/apache/spark/scheduler/TaskScheduler.scala
@@ -17,7 +17,6 @@
 
 package org.apache.spark.scheduler
 
-import org.apache.spark.executor.TaskMetrics
 import org.apache.spark.scheduler.SchedulingMode.SchedulingMode
 import org.apache.spark.storage.BlockManagerId
 
diff --git a/core/src/main/scala/org/apache/spark/scheduler/cluster/CoarseGrainedClusterMessage.scala b/core/src/main/scala/org/apache/spark/scheduler/cluster/CoarseGrainedClusterMessage.scala
index 29e469c3f5..8d5c11dc36 100644
--- a/core/src/main/scala/org/apache/spark/scheduler/cluster/CoarseGrainedClusterMessage.scala
+++ b/core/src/main/scala/org/apache/spark/scheduler/cluster/CoarseGrainedClusterMessage.scala
@@ -22,7 +22,7 @@ import java.nio.ByteBuffer
 import org.apache.spark.TaskState.TaskState
 import org.apache.spark.rpc.RpcEndpointRef
 import org.apache.spark.scheduler.ExecutorLossReason
-import org.apache.spark.util.{SerializableBuffer, Utils}
+import org.apache.spark.util.SerializableBuffer
 
 private[spark] sealed trait CoarseGrainedClusterMessage extends Serializable
 
diff --git a/core/src/main/scala/org/apache/spark/serializer/Serializer.scala b/core/src/main/scala/org/apache/spark/serializer/Serializer.scala
index 90c0728557..95bdf0ce2d 100644
--- a/core/src/main/scala/org/apache/spark/serializer/Serializer.scala
+++ b/core/src/main/scala/org/apache/spark/serializer/Serializer.scala
@@ -23,9 +23,9 @@ import javax.annotation.concurrent.NotThreadSafe
 
 import scala.reflect.ClassTag
 
-import org.apache.spark.{SparkConf, SparkEnv}
+import org.apache.spark.SparkEnv
 import org.apache.spark.annotation.{DeveloperApi, Private}
-import org.apache.spark.util.{ByteBufferInputStream, NextIterator, Utils}
+import org.apache.spark.util.NextIterator
 
 /**
  * :: DeveloperApi ::
diff --git a/core/src/main/scala/org/apache/spark/shuffle/BaseShuffleHandle.scala b/core/src/main/scala/org/apache/spark/shuffle/BaseShuffleHandle.scala
index 0a65bbf8dd..04e4cf88d7 100644
--- a/core/src/main/scala/org/apache/spark/shuffle/BaseShuffleHandle.scala
+++ b/core/src/main/scala/org/apache/spark/shuffle/BaseShuffleHandle.scala
@@ -17,8 +17,7 @@
 
 package org.apache.spark.shuffle
 
-import org.apache.spark.{Aggregator, Partitioner, ShuffleDependency}
-import org.apache.spark.serializer.Serializer
+import org.apache.spark.ShuffleDependency
 
 /**
  * A basic ShuffleHandle implementation that just captures registerShuffle's parameters.
diff --git a/core/src/main/scala/org/apache/spark/shuffle/ShuffleBlockResolver.scala b/core/src/main/scala/org/apache/spark/shuffle/ShuffleBlockResolver.scala
index 81aea33ee4..d1ecbc1bf0 100644
--- a/core/src/main/scala/org/apache/spark/shuffle/ShuffleBlockResolver.scala
+++ b/core/src/main/scala/org/apache/spark/shuffle/ShuffleBlockResolver.scala
@@ -17,8 +17,6 @@
 
 package org.apache.spark.shuffle
 
-import java.nio.ByteBuffer
-
 import org.apache.spark.network.buffer.ManagedBuffer
 import org.apache.spark.storage.ShuffleBlockId
 
diff --git a/core/src/main/scala/org/apache/spark/shuffle/hash/HashShuffleWriter.scala b/core/src/main/scala/org/apache/spark/shuffle/hash/HashShuffleWriter.scala
index 28bcced901..7694e950be 100644
--- a/core/src/main/scala/org/apache/spark/shuffle/hash/HashShuffleWriter.scala
+++ b/core/src/main/scala/org/apache/spark/shuffle/hash/HashShuffleWriter.scala
@@ -20,7 +20,6 @@ package org.apache.spark.shuffle.hash
 import java.io.IOException
 
 import org.apache.spark._
-import org.apache.spark.executor.ShuffleWriteMetrics
 import org.apache.spark.scheduler.MapStatus
 import org.apache.spark.serializer.Serializer
 import org.apache.spark.shuffle._
diff --git a/core/src/main/scala/org/apache/spark/shuffle/sort/SortShuffleWriter.scala b/core/src/main/scala/org/apache/spark/shuffle/sort/SortShuffleWriter.scala
index 7eb3d96037..4a7b1f07b6 100644
--- a/core/src/main/scala/org/apache/spark/shuffle/sort/SortShuffleWriter.scala
+++ b/core/src/main/scala/org/apache/spark/shuffle/sort/SortShuffleWriter.scala
@@ -18,7 +18,6 @@
 package org.apache.spark.shuffle.sort
 
 import org.apache.spark._
-import org.apache.spark.executor.ShuffleWriteMetrics
 import org.apache.spark.scheduler.MapStatus
 import org.apache.spark.shuffle.{BaseShuffleHandle, IndexShuffleBlockResolver, ShuffleWriter}
 import org.apache.spark.storage.ShuffleBlockId
diff --git a/core/src/main/scala/org/apache/spark/storage/BlockManagerMaster.scala b/core/src/main/scala/org/apache/spark/storage/BlockManagerMaster.scala
index 0b7aa599e9..1cb027a3f5 100644
--- a/core/src/main/scala/org/apache/spark/storage/BlockManagerMaster.scala
+++ b/core/src/main/scala/org/apache/spark/storage/BlockManagerMaster.scala
@@ -19,7 +19,7 @@ package org.apache.spark.storage
 
 import scala.collection.Iterable
 import scala.collection.generic.CanBuildFrom
-import scala.concurrent.{Await, Future}
+import scala.concurrent.Future
 
 import org.apache.spark.{Logging, SparkConf, SparkException}
 import org.apache.spark.rpc.RpcEndpointRef
diff --git a/core/src/main/scala/org/apache/spark/storage/DiskStore.scala b/core/src/main/scala/org/apache/spark/storage/DiskStore.scala
index bfa6560a72..db12a4a1b9 100644
--- a/core/src/main/scala/org/apache/spark/storage/DiskStore.scala
+++ b/core/src/main/scala/org/apache/spark/storage/DiskStore.scala
@@ -22,7 +22,6 @@ import java.nio.ByteBuffer
 import java.nio.channels.FileChannel.MapMode
 
 import org.apache.spark.Logging
-import org.apache.spark.serializer.Serializer
 import org.apache.spark.util.Utils
 
 /**
diff --git a/core/src/main/scala/org/apache/spark/ui/JettyUtils.scala b/core/src/main/scala/org/apache/spark/ui/JettyUtils.scala
index bc143b7de3..6b3601250a 100644
--- a/core/src/main/scala/org/apache/spark/ui/JettyUtils.scala
+++ b/core/src/main/scala/org/apache/spark/ui/JettyUtils.scala
@@ -21,7 +21,7 @@ import java.net.{URI, URL}
 import javax.servlet.DispatcherType
 import javax.servlet.http.{HttpServlet, HttpServletRequest, HttpServletResponse}
 
-import scala.collection.mutable.{ArrayBuffer, StringBuilder}
+import scala.collection.mutable.ArrayBuffer
 import scala.language.implicitConversions
 import scala.xml.Node
 
diff --git a/core/src/main/scala/org/apache/spark/ui/exec/ExecutorThreadDumpPage.scala b/core/src/main/scala/org/apache/spark/ui/exec/ExecutorThreadDumpPage.scala
index edc66709e2..cc476d61b5 100644
--- a/core/src/main/scala/org/apache/spark/ui/exec/ExecutorThreadDumpPage.scala
+++ b/core/src/main/scala/org/apache/spark/ui/exec/ExecutorThreadDumpPage.scala
@@ -19,7 +19,6 @@ package org.apache.spark.ui.exec
 
 import javax.servlet.http.HttpServletRequest
 
-import scala.util.Try
 import scala.xml.{Node, Text}
 
 import org.apache.spark.ui.{UIUtils, WebUIPage}
diff --git a/core/src/main/scala/org/apache/spark/util/SizeEstimator.scala b/core/src/main/scala/org/apache/spark/util/SizeEstimator.scala
index 52587d2188..83ded92609 100644
--- a/core/src/main/scala/org/apache/spark/util/SizeEstimator.scala
+++ b/core/src/main/scala/org/apache/spark/util/SizeEstimator.scala
@@ -20,7 +20,6 @@ package org.apache.spark.util
 import java.lang.management.ManagementFactory
 import java.lang.reflect.{Field, Modifier}
 import java.util.{IdentityHashMap, Random}
-import java.util.concurrent.ConcurrentHashMap
 
 import scala.collection.mutable.ArrayBuffer
 import scala.runtime.ScalaRunTime
diff --git a/core/src/main/scala/org/apache/spark/util/collection/AppendOnlyMap.scala b/core/src/main/scala/org/apache/spark/util/collection/AppendOnlyMap.scala
index 4c1e161554..6b74a29ace 100644
--- a/core/src/main/scala/org/apache/spark/util/collection/AppendOnlyMap.scala
+++ b/core/src/main/scala/org/apache/spark/util/collection/AppendOnlyMap.scala
@@ -17,7 +17,7 @@
 
 package org.apache.spark.util.collection
 
-import java.util.{Arrays, Comparator}
+import java.util.Comparator
 
 import com.google.common.hash.Hashing
 
diff --git a/core/src/test/java/org/apache/spark/launcher/SparkLauncherSuite.java b/core/src/test/java/org/apache/spark/launcher/SparkLauncherSuite.java
index aa15e792e2..1692df7d30 100644
--- a/core/src/test/java/org/apache/spark/launcher/SparkLauncherSuite.java
+++ b/core/src/test/java/org/apache/spark/launcher/SparkLauncherSuite.java
@@ -17,9 +17,6 @@
 
 package org.apache.spark.launcher;
 
-import java.io.BufferedReader;
-import java.io.InputStream;
-import java.io.InputStreamReader;
 import java.util.Arrays;
 import java.util.HashMap;
 import java.util.Map;
diff --git a/core/src/test/java/org/apache/spark/serializer/TestJavaSerializerImpl.java b/core/src/test/java/org/apache/spark/serializer/TestJavaSerializerImpl.java
index 3d50ab4fab..8aa0636700 100644
--- a/core/src/test/java/org/apache/spark/serializer/TestJavaSerializerImpl.java
+++ b/core/src/test/java/org/apache/spark/serializer/TestJavaSerializerImpl.java
@@ -21,7 +21,6 @@ import java.io.InputStream;
 import java.io.OutputStream;
 import java.nio.ByteBuffer;
 
-import scala.Option;
 import scala.reflect.ClassTag;
 
 
diff --git a/core/src/test/scala/org/apache/spark/MapOutputTrackerSuite.scala b/core/src/test/scala/org/apache/spark/MapOutputTrackerSuite.scala
index 6546def596..ddf48765ec 100644
--- a/core/src/test/scala/org/apache/spark/MapOutputTrackerSuite.scala
+++ b/core/src/test/scala/org/apache/spark/MapOutputTrackerSuite.scala
@@ -22,7 +22,7 @@ import scala.collection.mutable.ArrayBuffer
 import org.mockito.Matchers.{any, isA}
 import org.mockito.Mockito._
 
-import org.apache.spark.rpc.{RpcAddress, RpcCallContext, RpcEndpointRef, RpcEnv}
+import org.apache.spark.rpc.{RpcAddress, RpcCallContext, RpcEnv}
 import org.apache.spark.scheduler.{CompressedMapStatus, MapStatus}
 import org.apache.spark.shuffle.FetchFailedException
 import org.apache.spark.storage.{BlockManagerId, ShuffleBlockId}
diff --git a/core/src/test/scala/org/apache/spark/SSLOptionsSuite.scala b/core/src/test/scala/org/apache/spark/SSLOptionsSuite.scala
index fa35819f55..159b448e05 100644
--- a/core/src/test/scala/org/apache/spark/SSLOptionsSuite.scala
+++ b/core/src/test/scala/org/apache/spark/SSLOptionsSuite.scala
@@ -20,11 +20,8 @@ package org.apache.spark
 import java.io.File
 import javax.net.ssl.SSLContext
 
-import com.google.common.io.Files
 import org.scalatest.BeforeAndAfterAll
 
-import org.apache.spark.util.Utils
-
 class SSLOptionsSuite extends SparkFunSuite with BeforeAndAfterAll {
 
   test("test resolving property file as spark conf ") {
diff --git a/core/src/test/scala/org/apache/spark/ThreadingSuite.scala b/core/src/test/scala/org/apache/spark/ThreadingSuite.scala
index fc31b784c7..b66aba91c5 100644
--- a/core/src/test/scala/org/apache/spark/ThreadingSuite.scala
+++ b/core/src/test/scala/org/apache/spark/ThreadingSuite.scala
@@ -17,11 +17,9 @@
 
 package org.apache.spark
 
-import java.util.concurrent.{Semaphore, TimeUnit}
+import java.util.concurrent.Semaphore
 import java.util.concurrent.atomic.{AtomicBoolean, AtomicInteger}
 
-import org.apache.spark.scheduler._
-
 /**
  * Holds state shared across task threads in some ThreadingSuite tests.
  */
diff --git a/core/src/test/scala/org/apache/spark/deploy/LogUrlsStandaloneSuite.scala b/core/src/test/scala/org/apache/spark/deploy/LogUrlsStandaloneSuite.scala
index f416ace5c2..cbdf1755b0 100644
--- a/core/src/test/scala/org/apache/spark/deploy/LogUrlsStandaloneSuite.scala
+++ b/core/src/test/scala/org/apache/spark/deploy/LogUrlsStandaloneSuite.scala
@@ -22,7 +22,7 @@ import java.net.URL
 import scala.collection.mutable
 import scala.io.Source
 
-import org.apache.spark.{LocalSparkContext, SparkConf, SparkContext, SparkFunSuite}
+import org.apache.spark.{LocalSparkContext, SparkContext, SparkFunSuite}
 import org.apache.spark.scheduler.{SparkListener, SparkListenerExecutorAdded}
 import org.apache.spark.scheduler.cluster.ExecutorInfo
 import org.apache.spark.util.SparkConfWithEnv
diff --git a/core/src/test/scala/org/apache/spark/deploy/client/AppClientSuite.scala b/core/src/test/scala/org/apache/spark/deploy/client/AppClientSuite.scala
index 658779360b..379c038c55 100644
--- a/core/src/test/scala/org/apache/spark/deploy/client/AppClientSuite.scala
+++ b/core/src/test/scala/org/apache/spark/deploy/client/AppClientSuite.scala
@@ -19,7 +19,6 @@ package org.apache.spark.deploy.client
 
 import java.util.concurrent.ConcurrentLinkedQueue
 
-import scala.collection.JavaConverters._
 import scala.concurrent.duration._
 
 import org.scalatest.BeforeAndAfterAll
diff --git a/core/src/test/scala/org/apache/spark/deploy/history/FsHistoryProviderSuite.scala b/core/src/test/scala/org/apache/spark/deploy/history/FsHistoryProviderSuite.scala
index 3baa2e2dda..8e8007f4eb 100644
--- a/core/src/test/scala/org/apache/spark/deploy/history/FsHistoryProviderSuite.scala
+++ b/core/src/test/scala/org/apache/spark/deploy/history/FsHistoryProviderSuite.scala
@@ -24,16 +24,14 @@ import java.util.concurrent.TimeUnit
 import java.util.zip.{ZipInputStream, ZipOutputStream}
 
 import scala.concurrent.duration._
-import scala.io.Source
 import scala.language.postfixOps
 
 import com.google.common.base.Charsets
 import com.google.common.io.{ByteStreams, Files}
-import org.apache.hadoop.fs.Path
 import org.apache.hadoop.hdfs.DistributedFileSystem
 import org.json4s.jackson.JsonMethods._
 import org.mockito.Matchers.any
-import org.mockito.Mockito.{doReturn, mock, spy, verify, when}
+import org.mockito.Mockito.{mock, spy, verify}
 import org.scalatest.BeforeAndAfter
 import org.scalatest.Matchers
 import org.scalatest.concurrent.Eventually._
@@ -45,8 +43,6 @@ import org.apache.spark.util.{Clock, JsonProtocol, ManualClock, Utils}
 
 class FsHistoryProviderSuite extends SparkFunSuite with BeforeAndAfter with Matchers with Logging {
 
-  import FsHistoryProvider._
-
   private var testDir: File = null
 
   before {
diff --git a/core/src/test/scala/org/apache/spark/input/WholeTextFileRecordReaderSuite.scala b/core/src/test/scala/org/apache/spark/input/WholeTextFileRecordReaderSuite.scala
index d852255a4f..88b3a0e964 100644
--- a/core/src/test/scala/org/apache/spark/input/WholeTextFileRecordReaderSuite.scala
+++ b/core/src/test/scala/org/apache/spark/input/WholeTextFileRecordReaderSuite.scala
@@ -24,7 +24,7 @@ import java.io.FileOutputStream
 import scala.collection.immutable.IndexedSeq
 
 import org.apache.hadoop.io.Text
-import org.apache.hadoop.io.compress.{CompressionCodecFactory, DefaultCodec, GzipCodec}
+import org.apache.hadoop.io.compress.{CompressionCodecFactory, GzipCodec}
 import org.scalatest.BeforeAndAfterAll
 
 import org.apache.spark.{Logging, SparkConf, SparkContext, SparkFunSuite}
diff --git a/core/src/test/scala/org/apache/spark/launcher/LauncherBackendSuite.scala b/core/src/test/scala/org/apache/spark/launcher/LauncherBackendSuite.scala
index 639d1daa36..713560d3dd 100644
--- a/core/src/test/scala/org/apache/spark/launcher/LauncherBackendSuite.scala
+++ b/core/src/test/scala/org/apache/spark/launcher/LauncherBackendSuite.scala
@@ -26,7 +26,6 @@ import org.scalatest.Matchers
 import org.scalatest.concurrent.Eventually._
 
 import org.apache.spark._
-import org.apache.spark.launcher._
 
 class LauncherBackendSuite extends SparkFunSuite with Matchers {
 
diff --git a/core/src/test/scala/org/apache/spark/memory/TestMemoryManager.scala b/core/src/test/scala/org/apache/spark/memory/TestMemoryManager.scala
index e5cb9d3a99..6dad3f4ae7 100644
--- a/core/src/test/scala/org/apache/spark/memory/TestMemoryManager.scala
+++ b/core/src/test/scala/org/apache/spark/memory/TestMemoryManager.scala
@@ -17,10 +17,8 @@
 
 package org.apache.spark.memory
 
-import scala.collection.mutable
-
 import org.apache.spark.SparkConf
-import org.apache.spark.storage.{BlockId, BlockStatus}
+import org.apache.spark.storage.BlockId
 
 class TestMemoryManager(conf: SparkConf)
   extends MemoryManager(conf, numCores = 1, Long.MaxValue, Long.MaxValue) {
diff --git a/core/src/test/scala/org/apache/spark/rpc/RpcEnvSuite.scala b/core/src/test/scala/org/apache/spark/rpc/RpcEnvSuite.scala
index 2204800388..43e61241b6 100644
--- a/core/src/test/scala/org/apache/spark/rpc/RpcEnvSuite.scala
+++ b/core/src/test/scala/org/apache/spark/rpc/RpcEnvSuite.scala
@@ -20,7 +20,7 @@ package org.apache.spark.rpc
 import java.io.{File, NotSerializableException}
 import java.nio.charset.StandardCharsets.UTF_8
 import java.util.UUID
-import java.util.concurrent.{ConcurrentLinkedQueue, CountDownLatch, TimeoutException, TimeUnit}
+import java.util.concurrent.{ConcurrentLinkedQueue, CountDownLatch, TimeUnit}
 
 import scala.collection.mutable
 import scala.collection.JavaConverters._
diff --git a/core/src/test/scala/org/apache/spark/rpc/netty/InboxSuite.scala b/core/src/test/scala/org/apache/spark/rpc/netty/InboxSuite.scala
index 12113be75c..e5539566e4 100644
--- a/core/src/test/scala/org/apache/spark/rpc/netty/InboxSuite.scala
+++ b/core/src/test/scala/org/apache/spark/rpc/netty/InboxSuite.scala
@@ -23,7 +23,7 @@ import java.util.concurrent.atomic.AtomicInteger
 import org.mockito.Mockito._
 
 import org.apache.spark.SparkFunSuite
-import org.apache.spark.rpc.{RpcAddress, RpcEndpoint, RpcEnv, TestRpcEndpoint}
+import org.apache.spark.rpc.{RpcAddress, TestRpcEndpoint}
 
 class InboxSuite extends SparkFunSuite {
 
diff --git a/core/src/test/scala/org/apache/spark/scheduler/cluster/mesos/CoarseMesosSchedulerBackendSuite.scala b/core/src/test/scala/org/apache/spark/scheduler/cluster/mesos/CoarseMesosSchedulerBackendSuite.scala
index 5db7535d36..2df05401f3 100644
--- a/core/src/test/scala/org/apache/spark/scheduler/cluster/mesos/CoarseMesosSchedulerBackendSuite.scala
+++ b/core/src/test/scala/org/apache/spark/scheduler/cluster/mesos/CoarseMesosSchedulerBackendSuite.scala
@@ -33,7 +33,7 @@ import org.scalatest.BeforeAndAfter
 
 import org.apache.spark.{LocalSparkContext, SecurityManager, SparkConf, SparkContext, SparkFunSuite}
 import org.apache.spark.network.shuffle.mesos.MesosExternalShuffleClient
-import org.apache.spark.rpc.{RpcEndpointRef}
+import org.apache.spark.rpc.RpcEndpointRef
 import org.apache.spark.scheduler.TaskSchedulerImpl
 
 class CoarseMesosSchedulerBackendSuite extends SparkFunSuite
diff --git a/core/src/test/scala/org/apache/spark/ui/UISuite.scala b/core/src/test/scala/org/apache/spark/ui/UISuite.scala
index 69c46058f1..2b59b48d8b 100644
--- a/core/src/test/scala/org/apache/spark/ui/UISuite.scala
+++ b/core/src/test/scala/org/apache/spark/ui/UISuite.scala
@@ -21,7 +21,6 @@ import java.net.{BindException, ServerSocket}
 
 import scala.io.Source
 
-import org.eclipse.jetty.server.Server
 import org.eclipse.jetty.servlet.ServletContextHandler
 import org.scalatest.concurrent.Eventually._
 import org.scalatest.time.SpanSugar._
diff --git a/core/src/test/scala/org/apache/spark/util/ResetSystemProperties.scala b/core/src/test/scala/org/apache/spark/util/ResetSystemProperties.scala
index 60fb7abb66..75e4504850 100644
--- a/core/src/test/scala/org/apache/spark/util/ResetSystemProperties.scala
+++ b/core/src/test/scala/org/apache/spark/util/ResetSystemProperties.scala
@@ -22,8 +22,6 @@ import java.util.Properties
 import org.apache.commons.lang3.SerializationUtils
 import org.scalatest.{BeforeAndAfterEach, Suite}
 
-import org.apache.spark.SparkFunSuite
-
 /**
  * Mixin for automatically resetting system properties that are modified in ScalaTest tests.
  * This resets the properties after each individual test.
diff --git a/core/src/test/scala/org/apache/spark/util/SizeEstimatorSuite.scala b/core/src/test/scala/org/apache/spark/util/SizeEstimatorSuite.scala
index 49088aa0a5..c342b68f46 100644
--- a/core/src/test/scala/org/apache/spark/util/SizeEstimatorSuite.scala
+++ b/core/src/test/scala/org/apache/spark/util/SizeEstimatorSuite.scala
@@ -19,7 +19,7 @@ package org.apache.spark.util
 
 import scala.collection.mutable.ArrayBuffer
 
-import org.scalatest.{BeforeAndAfterAll, BeforeAndAfterEach, PrivateMethodTester}
+import org.scalatest.{BeforeAndAfterEach, PrivateMethodTester}
 
 import org.apache.spark.SparkFunSuite
 
diff --git a/docker-integration-tests/src/test/scala/org/apache/spark/sql/jdbc/OracleIntegrationSuite.scala b/docker-integration-tests/src/test/scala/org/apache/spark/sql/jdbc/OracleIntegrationSuite.scala
index b5416d7072..8a0f938f7e 100644
--- a/docker-integration-tests/src/test/scala/org/apache/spark/sql/jdbc/OracleIntegrationSuite.scala
+++ b/docker-integration-tests/src/test/scala/org/apache/spark/sql/jdbc/OracleIntegrationSuite.scala
@@ -17,12 +17,10 @@
 
 package org.apache.spark.sql.jdbc
 
-import java.math.BigDecimal
-import java.sql.{Connection, Date, Timestamp}
+import java.sql.Connection
 import java.util.Properties
 
 import org.apache.spark.sql.test.SharedSQLContext
-import org.apache.spark.sql.types._
 import org.apache.spark.tags.DockerTest
 
 /**
diff --git a/examples/src/main/java/org/apache/spark/examples/JavaLogQuery.java b/examples/src/main/java/org/apache/spark/examples/JavaLogQuery.java
index 0448a1a0c8..1a6caa8cf8 100644
--- a/examples/src/main/java/org/apache/spark/examples/JavaLogQuery.java
+++ b/examples/src/main/java/org/apache/spark/examples/JavaLogQuery.java
@@ -28,7 +28,6 @@ import org.apache.spark.api.java.function.Function2;
 import org.apache.spark.api.java.function.PairFunction;
 
 import java.io.Serializable;
-import java.util.Collections;
 import java.util.List;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
diff --git a/examples/src/main/java/org/apache/spark/examples/mllib/JavaMultiLabelClassificationMetricsExample.java b/examples/src/main/java/org/apache/spark/examples/mllib/JavaMultiLabelClassificationMetricsExample.java
index 5ba01e0d08..4717155438 100644
--- a/examples/src/main/java/org/apache/spark/examples/mllib/JavaMultiLabelClassificationMetricsExample.java
+++ b/examples/src/main/java/org/apache/spark/examples/mllib/JavaMultiLabelClassificationMetricsExample.java
@@ -25,10 +25,8 @@ import scala.Tuple2;
 
 import org.apache.spark.api.java.*;
 import org.apache.spark.mllib.evaluation.MultilabelMetrics;
-import org.apache.spark.rdd.RDD;
 import org.apache.spark.SparkConf;
 // $example off$
-import org.apache.spark.SparkContext;
 
 public class JavaMultiLabelClassificationMetricsExample {
   public static void main(String[] args) {
diff --git a/examples/src/main/scala/org/apache/spark/examples/DFSReadWriteTest.scala b/examples/src/main/scala/org/apache/spark/examples/DFSReadWriteTest.scala
index e37a3fa69d..743fc13db7 100644
--- a/examples/src/main/scala/org/apache/spark/examples/DFSReadWriteTest.scala
+++ b/examples/src/main/scala/org/apache/spark/examples/DFSReadWriteTest.scala
@@ -23,7 +23,6 @@ import java.io.File
 import scala.io.Source._
 
 import org.apache.spark.{SparkConf, SparkContext}
-import org.apache.spark.SparkContext._
 
 /**
   * Simple test for reading and writing to a distributed
diff --git a/examples/src/main/scala/org/apache/spark/examples/GroupByTest.scala b/examples/src/main/scala/org/apache/spark/examples/GroupByTest.scala
index fa4a3afeec..08b6c717d4 100644
--- a/examples/src/main/scala/org/apache/spark/examples/GroupByTest.scala
+++ b/examples/src/main/scala/org/apache/spark/examples/GroupByTest.scala
@@ -21,7 +21,6 @@ package org.apache.spark.examples
 import java.util.Random
 
 import org.apache.spark.{SparkConf, SparkContext}
-import org.apache.spark.SparkContext._
 
 /**
   * Usage: GroupByTest [numMappers] [numKVPairs] [KeySize] [numReducers]
diff --git a/examples/src/main/scala/org/apache/spark/examples/LocalKMeans.scala b/examples/src/main/scala/org/apache/spark/examples/LocalKMeans.scala
index 407e3e08b9..19bebffcb0 100644
--- a/examples/src/main/scala/org/apache/spark/examples/LocalKMeans.scala
+++ b/examples/src/main/scala/org/apache/spark/examples/LocalKMeans.scala
@@ -25,8 +25,6 @@ import scala.collection.mutable.HashSet
 
 import breeze.linalg.{squaredDistance, DenseVector, Vector}
 
-import org.apache.spark.SparkContext._
-
 /**
  * K-means clustering.
  *
diff --git a/examples/src/main/scala/org/apache/spark/examples/LocalPi.scala b/examples/src/main/scala/org/apache/spark/examples/LocalPi.scala
index 3d923625f1..720d92fb9d 100644
--- a/examples/src/main/scala/org/apache/spark/examples/LocalPi.scala
+++ b/examples/src/main/scala/org/apache/spark/examples/LocalPi.scala
@@ -20,9 +20,6 @@ package org.apache.spark.examples
 
 import scala.math.random
 
-import org.apache.spark._
-import org.apache.spark.SparkContext._
-
 object LocalPi {
   def main(args: Array[String]) {
     var count = 0
diff --git a/examples/src/main/scala/org/apache/spark/examples/LogQuery.scala b/examples/src/main/scala/org/apache/spark/examples/LogQuery.scala
index a80de10f46..c55b68e033 100644
--- a/examples/src/main/scala/org/apache/spark/examples/LogQuery.scala
+++ b/examples/src/main/scala/org/apache/spark/examples/LogQuery.scala
@@ -19,7 +19,6 @@
 package org.apache.spark.examples
 
 import org.apache.spark.{SparkConf, SparkContext}
-import org.apache.spark.SparkContext._
 
 /**
  * Executes a roll up-style query against Apache logs.
diff --git a/examples/src/main/scala/org/apache/spark/examples/SimpleSkewedGroupByTest.scala b/examples/src/main/scala/org/apache/spark/examples/SimpleSkewedGroupByTest.scala
index 3b0b00fe4d..7c09664c2f 100644
--- a/examples/src/main/scala/org/apache/spark/examples/SimpleSkewedGroupByTest.scala
+++ b/examples/src/main/scala/org/apache/spark/examples/SimpleSkewedGroupByTest.scala
@@ -21,7 +21,6 @@ package org.apache.spark.examples
 import java.util.Random
 
 import org.apache.spark.{SparkConf, SparkContext}
-import org.apache.spark.SparkContext._
 
 /**
   * Usage: SimpleSkewedGroupByTest [numMappers] [numKVPairs] [valSize] [numReducers] [ratio]
diff --git a/examples/src/main/scala/org/apache/spark/examples/SkewedGroupByTest.scala b/examples/src/main/scala/org/apache/spark/examples/SkewedGroupByTest.scala
index 719e2176fe..7796f362bb 100644
--- a/examples/src/main/scala/org/apache/spark/examples/SkewedGroupByTest.scala
+++ b/examples/src/main/scala/org/apache/spark/examples/SkewedGroupByTest.scala
@@ -21,7 +21,6 @@ package org.apache.spark.examples
 import java.util.Random
 
 import org.apache.spark.{SparkConf, SparkContext}
-import org.apache.spark.SparkContext._
 
 /**
   * Usage: GroupByTest [numMappers] [numKVPairs] [KeySize] [numReducers]
diff --git a/examples/src/main/scala/org/apache/spark/examples/SparkKMeans.scala b/examples/src/main/scala/org/apache/spark/examples/SparkKMeans.scala
index 1ea9121e27..d9f94a42b1 100644
--- a/examples/src/main/scala/org/apache/spark/examples/SparkKMeans.scala
+++ b/examples/src/main/scala/org/apache/spark/examples/SparkKMeans.scala
@@ -21,7 +21,6 @@ package org.apache.spark.examples
 import breeze.linalg.{squaredDistance, DenseVector, Vector}
 
 import org.apache.spark.{SparkConf, SparkContext}
-import org.apache.spark.SparkContext._
 
 /**
  * K-means clustering.
diff --git a/examples/src/main/scala/org/apache/spark/examples/SparkPageRank.scala b/examples/src/main/scala/org/apache/spark/examples/SparkPageRank.scala
index 018bdf6d31..2664ddbb87 100644
--- a/examples/src/main/scala/org/apache/spark/examples/SparkPageRank.scala
+++ b/examples/src/main/scala/org/apache/spark/examples/SparkPageRank.scala
@@ -19,7 +19,6 @@
 package org.apache.spark.examples
 
 import org.apache.spark.{SparkConf, SparkContext}
-import org.apache.spark.SparkContext._
 
 /**
  * Computes the PageRank of URLs from an input file. Input file should
diff --git a/examples/src/main/scala/org/apache/spark/examples/SparkTC.scala b/examples/src/main/scala/org/apache/spark/examples/SparkTC.scala
index b92740f1fb..fc7a1f859f 100644
--- a/examples/src/main/scala/org/apache/spark/examples/SparkTC.scala
+++ b/examples/src/main/scala/org/apache/spark/examples/SparkTC.scala
@@ -22,7 +22,6 @@ import scala.collection.mutable
 import scala.util.Random
 
 import org.apache.spark.{SparkConf, SparkContext}
-import org.apache.spark.SparkContext._
 
 /**
  * Transitive closure on a graph.
diff --git a/examples/src/main/scala/org/apache/spark/examples/graphx/SynthBenchmark.scala b/examples/src/main/scala/org/apache/spark/examples/graphx/SynthBenchmark.scala
index 41ca5cbb9f..6d2228c874 100644
--- a/examples/src/main/scala/org/apache/spark/examples/graphx/SynthBenchmark.scala
+++ b/examples/src/main/scala/org/apache/spark/examples/graphx/SynthBenchmark.scala
@@ -21,7 +21,6 @@ package org.apache.spark.examples.graphx
 import java.io.{FileOutputStream, PrintWriter}
 
 import org.apache.spark.{SparkConf, SparkContext}
-import org.apache.spark.SparkContext._
 import org.apache.spark.graphx.{GraphXUtils, PartitionStrategy}
 import org.apache.spark.graphx.util.GraphGenerators
 
diff --git a/examples/src/main/scala/org/apache/spark/examples/ml/LinearRegressionExample.scala b/examples/src/main/scala/org/apache/spark/examples/ml/LinearRegressionExample.scala
index 50998c94de..25be87811d 100644
--- a/examples/src/main/scala/org/apache/spark/examples/ml/LinearRegressionExample.scala
+++ b/examples/src/main/scala/org/apache/spark/examples/ml/LinearRegressionExample.scala
@@ -18,15 +18,13 @@
 // scalastyle:off println
 package org.apache.spark.examples.ml
 
-import scala.collection.mutable
 import scala.language.reflectiveCalls
 
 import scopt.OptionParser
 
 import org.apache.spark.{SparkConf, SparkContext}
 import org.apache.spark.examples.mllib.AbstractParams
-import org.apache.spark.ml.{Pipeline, PipelineStage}
-import org.apache.spark.ml.regression.{LinearRegression, LinearRegressionModel}
+import org.apache.spark.ml.regression.LinearRegression
 import org.apache.spark.sql.DataFrame
 
 /**
diff --git a/examples/src/main/scala/org/apache/spark/examples/mllib/CosineSimilarity.scala b/examples/src/main/scala/org/apache/spark/examples/mllib/CosineSimilarity.scala
index eda211b5a8..5ff3d36242 100644
--- a/examples/src/main/scala/org/apache/spark/examples/mllib/CosineSimilarity.scala
+++ b/examples/src/main/scala/org/apache/spark/examples/mllib/CosineSimilarity.scala
@@ -21,7 +21,6 @@ package org.apache.spark.examples.mllib
 import scopt.OptionParser
 
 import org.apache.spark.{SparkConf, SparkContext}
-import org.apache.spark.SparkContext._
 import org.apache.spark.mllib.linalg.Vectors
 import org.apache.spark.mllib.linalg.distributed.{MatrixEntry, RowMatrix}
 
diff --git a/examples/src/main/scala/org/apache/spark/examples/mllib/MovieLensALS.scala b/examples/src/main/scala/org/apache/spark/examples/mllib/MovieLensALS.scala
index 69691ae297..09750e53cb 100644
--- a/examples/src/main/scala/org/apache/spark/examples/mllib/MovieLensALS.scala
+++ b/examples/src/main/scala/org/apache/spark/examples/mllib/MovieLensALS.scala
@@ -24,7 +24,6 @@ import org.apache.log4j.{Level, Logger}
 import scopt.OptionParser
 
 import org.apache.spark.{SparkConf, SparkContext}
-import org.apache.spark.SparkContext._
 import org.apache.spark.mllib.recommendation.{ALS, MatrixFactorizationModel, Rating}
 import org.apache.spark.rdd.RDD
 
diff --git a/examples/src/main/scala/org/apache/spark/examples/mllib/SampledRDDs.scala b/examples/src/main/scala/org/apache/spark/examples/mllib/SampledRDDs.scala
index 011db4fd0c..0da4005977 100644
--- a/examples/src/main/scala/org/apache/spark/examples/mllib/SampledRDDs.scala
+++ b/examples/src/main/scala/org/apache/spark/examples/mllib/SampledRDDs.scala
@@ -21,7 +21,6 @@ package org.apache.spark.examples.mllib
 import scopt.OptionParser
 
 import org.apache.spark.{SparkConf, SparkContext}
-import org.apache.spark.SparkContext._
 import org.apache.spark.mllib.util.MLUtils
 
 /**
diff --git a/examples/src/main/scala/org/apache/spark/examples/streaming/ActorWordCount.scala b/examples/src/main/scala/org/apache/spark/examples/streaming/ActorWordCount.scala
index 9f7c7d50e5..2770b8af1c 100644
--- a/examples/src/main/scala/org/apache/spark/examples/streaming/ActorWordCount.scala
+++ b/examples/src/main/scala/org/apache/spark/examples/streaming/ActorWordCount.scala
@@ -19,7 +19,6 @@
 package org.apache.spark.examples.streaming
 
 import scala.collection.mutable.LinkedHashSet
-import scala.reflect.ClassTag
 import scala.util.Random
 
 import akka.actor._
diff --git a/examples/src/main/scala/org/apache/spark/examples/streaming/CustomReceiver.scala b/examples/src/main/scala/org/apache/spark/examples/streaming/CustomReceiver.scala
index ad13d437dd..5ce5778e42 100644
--- a/examples/src/main/scala/org/apache/spark/examples/streaming/CustomReceiver.scala
+++ b/examples/src/main/scala/org/apache/spark/examples/streaming/CustomReceiver.scala
@@ -18,7 +18,7 @@
 // scalastyle:off println
 package org.apache.spark.examples.streaming
 
-import java.io.{BufferedReader, InputStream, InputStreamReader}
+import java.io.{BufferedReader, InputStreamReader}
 import java.net.Socket
 
 import org.apache.spark.{Logging, SparkConf}
diff --git a/examples/src/main/scala/org/apache/spark/examples/streaming/FlumePollingEventCount.scala b/examples/src/main/scala/org/apache/spark/examples/streaming/FlumePollingEventCount.scala
index fe3b79ed5d..dd725d72c2 100644
--- a/examples/src/main/scala/org/apache/spark/examples/streaming/FlumePollingEventCount.scala
+++ b/examples/src/main/scala/org/apache/spark/examples/streaming/FlumePollingEventCount.scala
@@ -18,10 +18,7 @@
 // scalastyle:off println
 package org.apache.spark.examples.streaming
 
-import java.net.InetSocketAddress
-
 import org.apache.spark.SparkConf
-import org.apache.spark.storage.StorageLevel
 import org.apache.spark.streaming._
 import org.apache.spark.streaming.flume._
 import org.apache.spark.util.IntParam
diff --git a/examples/src/main/scala/org/apache/spark/examples/streaming/SqlNetworkWordCount.scala b/examples/src/main/scala/org/apache/spark/examples/streaming/SqlNetworkWordCount.scala
index 9aa0f54312..3727f8fe6a 100644
--- a/examples/src/main/scala/org/apache/spark/examples/streaming/SqlNetworkWordCount.scala
+++ b/examples/src/main/scala/org/apache/spark/examples/streaming/SqlNetworkWordCount.scala
@@ -24,7 +24,6 @@ import org.apache.spark.rdd.RDD
 import org.apache.spark.sql.SQLContext
 import org.apache.spark.storage.StorageLevel
 import org.apache.spark.streaming.{Seconds, StreamingContext, Time}
-import org.apache.spark.util.IntParam
 
 /**
  * Use DataFrames and SQL to count words in UTF8 encoded, '\n' delimited text received from the
diff --git a/examples/src/main/scala/org/apache/spark/examples/streaming/StatefulNetworkWordCount.scala b/examples/src/main/scala/org/apache/spark/examples/streaming/StatefulNetworkWordCount.scala
index c85d6843dc..2811e67009 100644
--- a/examples/src/main/scala/org/apache/spark/examples/streaming/StatefulNetworkWordCount.scala
+++ b/examples/src/main/scala/org/apache/spark/examples/streaming/StatefulNetworkWordCount.scala
@@ -18,7 +18,6 @@
 // scalastyle:off println
 package org.apache.spark.examples.streaming
 
-import org.apache.spark.HashPartitioner
 import org.apache.spark.SparkConf
 import org.apache.spark.streaming._
 
diff --git a/examples/src/main/scala/org/apache/spark/examples/streaming/TwitterAlgebirdCMS.scala b/examples/src/main/scala/org/apache/spark/examples/streaming/TwitterAlgebirdCMS.scala
index 825c671a92..5af82e161a 100644
--- a/examples/src/main/scala/org/apache/spark/examples/streaming/TwitterAlgebirdCMS.scala
+++ b/examples/src/main/scala/org/apache/spark/examples/streaming/TwitterAlgebirdCMS.scala
@@ -22,7 +22,6 @@ import com.twitter.algebird._
 import com.twitter.algebird.CMSHasherImplicits._
 
 import org.apache.spark.SparkConf
-import org.apache.spark.SparkContext._
 import org.apache.spark.storage.StorageLevel
 import org.apache.spark.streaming.{Seconds, StreamingContext}
 import org.apache.spark.streaming.twitter._
diff --git a/examples/src/main/scala/org/apache/spark/examples/streaming/TwitterPopularTags.scala b/examples/src/main/scala/org/apache/spark/examples/streaming/TwitterPopularTags.scala
index 49cee1b43c..c386e39d52 100644
--- a/examples/src/main/scala/org/apache/spark/examples/streaming/TwitterPopularTags.scala
+++ b/examples/src/main/scala/org/apache/spark/examples/streaming/TwitterPopularTags.scala
@@ -19,7 +19,6 @@
 package org.apache.spark.examples.streaming
 
 import org.apache.spark.streaming.{Seconds, StreamingContext}
-import org.apache.spark.SparkContext._
 import org.apache.spark.streaming.twitter._
 import org.apache.spark.SparkConf
 
diff --git a/examples/src/main/scala/org/apache/spark/examples/streaming/ZeroMQWordCount.scala b/examples/src/main/scala/org/apache/spark/examples/streaming/ZeroMQWordCount.scala
index f612e508eb..99b561750b 100644
--- a/examples/src/main/scala/org/apache/spark/examples/streaming/ZeroMQWordCount.scala
+++ b/examples/src/main/scala/org/apache/spark/examples/streaming/ZeroMQWordCount.scala
@@ -25,9 +25,8 @@ import akka.actor.actorRef2Scala
 import akka.util.ByteString
 import akka.zeromq._
 import akka.zeromq.Subscribe
-import com.typesafe.config.ConfigFactory
 
-import org.apache.spark.{SparkConf, TaskContext}
+import org.apache.spark.SparkConf
 import org.apache.spark.streaming.{Seconds, StreamingContext}
 import org.apache.spark.streaming.zeromq._
 
diff --git a/external/flume/src/test/scala/org/apache/spark/streaming/TestOutputStream.scala b/external/flume/src/test/scala/org/apache/spark/streaming/TestOutputStream.scala
index fc02c9fcb5..c97a27ca7c 100644
--- a/external/flume/src/test/scala/org/apache/spark/streaming/TestOutputStream.scala
+++ b/external/flume/src/test/scala/org/apache/spark/streaming/TestOutputStream.scala
@@ -20,7 +20,6 @@ package org.apache.spark.streaming
 import java.io.{IOException, ObjectInputStream}
 import java.util.concurrent.ConcurrentLinkedQueue
 
-import scala.collection.mutable.ArrayBuffer
 import scala.reflect.ClassTag
 
 import org.apache.spark.rdd.RDD
diff --git a/external/mqtt/src/test/scala/org/apache/spark/streaming/mqtt/MQTTStreamSuite.scala b/external/mqtt/src/test/scala/org/apache/spark/streaming/mqtt/MQTTStreamSuite.scala
index a6a9249db8..fdcd18c6fb 100644
--- a/external/mqtt/src/test/scala/org/apache/spark/streaming/mqtt/MQTTStreamSuite.scala
+++ b/external/mqtt/src/test/scala/org/apache/spark/streaming/mqtt/MQTTStreamSuite.scala
@@ -23,7 +23,7 @@ import scala.language.postfixOps
 import org.scalatest.BeforeAndAfter
 import org.scalatest.concurrent.Eventually
 
-import org.apache.spark.{SparkConf, SparkFunSuite}
+import org.apache.spark.SparkFunSuite
 import org.apache.spark.storage.StorageLevel
 import org.apache.spark.streaming.{Milliseconds, StreamingContext}
 
diff --git a/external/twitter/src/main/scala/org/apache/spark/streaming/twitter/TwitterUtils.scala b/external/twitter/src/main/scala/org/apache/spark/streaming/twitter/TwitterUtils.scala
index 3e843e947d..9cb0106ab1 100644
--- a/external/twitter/src/main/scala/org/apache/spark/streaming/twitter/TwitterUtils.scala
+++ b/external/twitter/src/main/scala/org/apache/spark/streaming/twitter/TwitterUtils.scala
@@ -22,8 +22,8 @@ import twitter4j.auth.Authorization
 
 import org.apache.spark.storage.StorageLevel
 import org.apache.spark.streaming.StreamingContext
-import org.apache.spark.streaming.api.java.{JavaDStream, JavaReceiverInputDStream, JavaStreamingContext}
-import org.apache.spark.streaming.dstream.{DStream, ReceiverInputDStream}
+import org.apache.spark.streaming.api.java.{JavaReceiverInputDStream, JavaStreamingContext}
+import org.apache.spark.streaming.dstream.ReceiverInputDStream
 
 object TwitterUtils {
   /**
diff --git a/graphx/src/main/scala/org/apache/spark/graphx/GraphOps.scala b/graphx/src/main/scala/org/apache/spark/graphx/GraphOps.scala
index 87f3bc31e6..d537b6141c 100644
--- a/graphx/src/main/scala/org/apache/spark/graphx/GraphOps.scala
+++ b/graphx/src/main/scala/org/apache/spark/graphx/GraphOps.scala
@@ -17,15 +17,10 @@
 
 package org.apache.spark.graphx
 
-import scala.reflect.{classTag, ClassTag}
 import scala.reflect.ClassTag
 import scala.util.Random
 
-import org.apache.spark.HashPartitioner
-import org.apache.spark.SparkContext._
 import org.apache.spark.SparkException
-import org.apache.spark.graphx.impl.EdgePartitionBuilder
-import org.apache.spark.graphx.impl.GraphImpl
 import org.apache.spark.graphx.lib._
 import org.apache.spark.rdd.RDD
 
diff --git a/graphx/src/main/scala/org/apache/spark/graphx/VertexRDD.scala b/graphx/src/main/scala/org/apache/spark/graphx/VertexRDD.scala
index 5a0c479bb4..35577d9e2f 100644
--- a/graphx/src/main/scala/org/apache/spark/graphx/VertexRDD.scala
+++ b/graphx/src/main/scala/org/apache/spark/graphx/VertexRDD.scala
@@ -20,7 +20,6 @@ package org.apache.spark.graphx
 import scala.reflect.ClassTag
 
 import org.apache.spark._
-import org.apache.spark.SparkContext._
 import org.apache.spark.graphx.impl.RoutingTablePartition
 import org.apache.spark.graphx.impl.ShippableVertexPartition
 import org.apache.spark.graphx.impl.VertexAttributeBlock
diff --git a/graphx/src/main/scala/org/apache/spark/graphx/impl/EdgePartition.scala b/graphx/src/main/scala/org/apache/spark/graphx/impl/EdgePartition.scala
index b1da781663..26349f4d88 100644
--- a/graphx/src/main/scala/org/apache/spark/graphx/impl/EdgePartition.scala
+++ b/graphx/src/main/scala/org/apache/spark/graphx/impl/EdgePartition.scala
@@ -17,7 +17,7 @@
 
 package org.apache.spark.graphx.impl
 
-import scala.reflect.{classTag, ClassTag}
+import scala.reflect.ClassTag
 
 import org.apache.spark.graphx._
 import org.apache.spark.graphx.util.collection.GraphXPrimitiveKeyOpenHashMap
diff --git a/graphx/src/main/scala/org/apache/spark/graphx/impl/ReplicatedVertexView.scala b/graphx/src/main/scala/org/apache/spark/graphx/impl/ReplicatedVertexView.scala
index b4bec7cba5..d2194d85bf 100644
--- a/graphx/src/main/scala/org/apache/spark/graphx/impl/ReplicatedVertexView.scala
+++ b/graphx/src/main/scala/org/apache/spark/graphx/impl/ReplicatedVertexView.scala
@@ -17,9 +17,8 @@
 
 package org.apache.spark.graphx.impl
 
-import scala.reflect.{classTag, ClassTag}
+import scala.reflect.ClassTag
 
-import org.apache.spark.SparkContext._
 import org.apache.spark.graphx._
 import org.apache.spark.rdd.RDD
 
diff --git a/graphx/src/main/scala/org/apache/spark/graphx/impl/RoutingTablePartition.scala b/graphx/src/main/scala/org/apache/spark/graphx/impl/RoutingTablePartition.scala
index 13e25b43f6..6453bbeae9 100644
--- a/graphx/src/main/scala/org/apache/spark/graphx/impl/RoutingTablePartition.scala
+++ b/graphx/src/main/scala/org/apache/spark/graphx/impl/RoutingTablePartition.scala
@@ -17,14 +17,8 @@
 
 package org.apache.spark.graphx.impl
 
-import scala.reflect.ClassTag
-
-import org.apache.spark.Partitioner
 import org.apache.spark.graphx._
-import org.apache.spark.graphx.impl.RoutingTablePartition.RoutingTableMessage
 import org.apache.spark.graphx.util.collection.GraphXPrimitiveKeyOpenHashMap
-import org.apache.spark.rdd.RDD
-import org.apache.spark.rdd.ShuffledRDD
 import org.apache.spark.util.collection.{BitSet, PrimitiveVector}
 
 private[graphx]
diff --git a/graphx/src/main/scala/org/apache/spark/graphx/impl/VertexPartition.scala b/graphx/src/main/scala/org/apache/spark/graphx/impl/VertexPartition.scala
index 4512bc1739..b4100bade0 100644
--- a/graphx/src/main/scala/org/apache/spark/graphx/impl/VertexPartition.scala
+++ b/graphx/src/main/scala/org/apache/spark/graphx/impl/VertexPartition.scala
@@ -20,7 +20,6 @@ package org.apache.spark.graphx.impl
 import scala.reflect.ClassTag
 
 import org.apache.spark.graphx._
-import org.apache.spark.graphx.util.collection.GraphXPrimitiveKeyOpenHashMap
 import org.apache.spark.util.collection.BitSet
 
 private[graphx] object VertexPartition {
diff --git a/graphx/src/main/scala/org/apache/spark/graphx/impl/VertexRDDImpl.scala b/graphx/src/main/scala/org/apache/spark/graphx/impl/VertexRDDImpl.scala
index d5accdfbf7..d314522de9 100644
--- a/graphx/src/main/scala/org/apache/spark/graphx/impl/VertexRDDImpl.scala
+++ b/graphx/src/main/scala/org/apache/spark/graphx/impl/VertexRDDImpl.scala
@@ -20,7 +20,6 @@ package org.apache.spark.graphx.impl
 import scala.reflect.ClassTag
 
 import org.apache.spark._
-import org.apache.spark.SparkContext._
 import org.apache.spark.graphx._
 import org.apache.spark.rdd._
 import org.apache.spark.storage.StorageLevel
diff --git a/graphx/src/main/scala/org/apache/spark/graphx/lib/TriangleCount.scala b/graphx/src/main/scala/org/apache/spark/graphx/lib/TriangleCount.scala
index 026fb8bc7b..34e9e22c3a 100644
--- a/graphx/src/main/scala/org/apache/spark/graphx/lib/TriangleCount.scala
+++ b/graphx/src/main/scala/org/apache/spark/graphx/lib/TriangleCount.scala
@@ -20,7 +20,6 @@ package org.apache.spark.graphx.lib
 import scala.reflect.ClassTag
 
 import org.apache.spark.graphx._
-import org.apache.spark.graphx.PartitionStrategy.EdgePartition2D
 
 /**
  * Compute the number of triangles passing through each vertex.
diff --git a/graphx/src/main/scala/org/apache/spark/graphx/util/GraphGenerators.scala b/graphx/src/main/scala/org/apache/spark/graphx/util/GraphGenerators.scala
index 95522299f0..ba67c66f86 100644
--- a/graphx/src/main/scala/org/apache/spark/graphx/util/GraphGenerators.scala
+++ b/graphx/src/main/scala/org/apache/spark/graphx/util/GraphGenerators.scala
@@ -18,16 +18,12 @@
 package org.apache.spark.graphx.util
 
 import scala.annotation.tailrec
-import scala.math._
 import scala.reflect.ClassTag
 import scala.util._
 
 import org.apache.spark._
-import org.apache.spark.SparkContext._
 import org.apache.spark.graphx._
-import org.apache.spark.graphx.impl.GraphImpl
 import org.apache.spark.rdd.RDD
-import org.apache.spark.serializer._
 
 /** A collection of graph generating functions. */
 object GraphGenerators extends Logging {
diff --git a/graphx/src/test/scala/org/apache/spark/graphx/GraphOpsSuite.scala b/graphx/src/test/scala/org/apache/spark/graphx/GraphOpsSuite.scala
index 3967f6683d..3298171949 100644
--- a/graphx/src/test/scala/org/apache/spark/graphx/GraphOpsSuite.scala
+++ b/graphx/src/test/scala/org/apache/spark/graphx/GraphOpsSuite.scala
@@ -19,8 +19,6 @@ package org.apache.spark.graphx
 
 import org.apache.spark.{SparkContext, SparkFunSuite}
 import org.apache.spark.graphx.Graph._
-import org.apache.spark.graphx.impl.EdgePartition
-import org.apache.spark.rdd._
 
 class GraphOpsSuite extends SparkFunSuite with LocalSparkContext {
 
diff --git a/graphx/src/test/scala/org/apache/spark/graphx/PregelSuite.scala b/graphx/src/test/scala/org/apache/spark/graphx/PregelSuite.scala
index 8afa2d403b..90a9ac613e 100644
--- a/graphx/src/test/scala/org/apache/spark/graphx/PregelSuite.scala
+++ b/graphx/src/test/scala/org/apache/spark/graphx/PregelSuite.scala
@@ -17,8 +17,7 @@
 
 package org.apache.spark.graphx
 
-import org.apache.spark.{SparkContext, SparkFunSuite}
-import org.apache.spark.rdd._
+import org.apache.spark.SparkFunSuite
 
 class PregelSuite extends SparkFunSuite with LocalSparkContext {
 
diff --git a/graphx/src/test/scala/org/apache/spark/graphx/impl/EdgePartitionSuite.scala b/graphx/src/test/scala/org/apache/spark/graphx/impl/EdgePartitionSuite.scala
index a73dfd219e..e4678b3578 100644
--- a/graphx/src/test/scala/org/apache/spark/graphx/impl/EdgePartitionSuite.scala
+++ b/graphx/src/test/scala/org/apache/spark/graphx/impl/EdgePartitionSuite.scala
@@ -18,7 +18,6 @@
 package org.apache.spark.graphx.impl
 
 import scala.reflect.ClassTag
-import scala.util.Random
 
 import org.apache.spark.{SparkConf, SparkFunSuite}
 import org.apache.spark.graphx._
diff --git a/graphx/src/test/scala/org/apache/spark/graphx/lib/ConnectedComponentsSuite.scala b/graphx/src/test/scala/org/apache/spark/graphx/lib/ConnectedComponentsSuite.scala
index c965a6eb8d..1b81423563 100644
--- a/graphx/src/test/scala/org/apache/spark/graphx/lib/ConnectedComponentsSuite.scala
+++ b/graphx/src/test/scala/org/apache/spark/graphx/lib/ConnectedComponentsSuite.scala
@@ -17,8 +17,7 @@
 
 package org.apache.spark.graphx.lib
 
-import org.apache.spark.{SparkContext, SparkFunSuite}
-import org.apache.spark.SparkContext._
+import org.apache.spark.SparkFunSuite
 import org.apache.spark.graphx._
 import org.apache.spark.graphx.util.GraphGenerators
 import org.apache.spark.rdd._
diff --git a/graphx/src/test/scala/org/apache/spark/graphx/lib/ShortestPathsSuite.scala b/graphx/src/test/scala/org/apache/spark/graphx/lib/ShortestPathsSuite.scala
index d7eaa70ce6..994395bbff 100644
--- a/graphx/src/test/scala/org/apache/spark/graphx/lib/ShortestPathsSuite.scala
+++ b/graphx/src/test/scala/org/apache/spark/graphx/lib/ShortestPathsSuite.scala
@@ -17,12 +17,8 @@
 
 package org.apache.spark.graphx.lib
 
-import org.apache.spark.{SparkContext, SparkFunSuite}
-import org.apache.spark.SparkContext._
+import org.apache.spark.SparkFunSuite
 import org.apache.spark.graphx._
-import org.apache.spark.graphx.lib._
-import org.apache.spark.graphx.util.GraphGenerators
-import org.apache.spark.rdd._
 
 class ShortestPathsSuite extends SparkFunSuite with LocalSparkContext {
 
diff --git a/graphx/src/test/scala/org/apache/spark/graphx/lib/StronglyConnectedComponentsSuite.scala b/graphx/src/test/scala/org/apache/spark/graphx/lib/StronglyConnectedComponentsSuite.scala
index d6b0320818..2c57e8927e 100644
--- a/graphx/src/test/scala/org/apache/spark/graphx/lib/StronglyConnectedComponentsSuite.scala
+++ b/graphx/src/test/scala/org/apache/spark/graphx/lib/StronglyConnectedComponentsSuite.scala
@@ -17,11 +17,8 @@
 
 package org.apache.spark.graphx.lib
 
-import org.apache.spark.{SparkContext, SparkFunSuite}
-import org.apache.spark.SparkContext._
+import org.apache.spark.SparkFunSuite
 import org.apache.spark.graphx._
-import org.apache.spark.graphx.util.GraphGenerators
-import org.apache.spark.rdd._
 
 
 class StronglyConnectedComponentsSuite extends SparkFunSuite with LocalSparkContext {
diff --git a/launcher/src/main/java/org/apache/spark/launcher/AbstractCommandBuilder.java b/launcher/src/main/java/org/apache/spark/launcher/AbstractCommandBuilder.java
index 45c2c008f6..c7ab51357c 100644
--- a/launcher/src/main/java/org/apache/spark/launcher/AbstractCommandBuilder.java
+++ b/launcher/src/main/java/org/apache/spark/launcher/AbstractCommandBuilder.java
@@ -25,12 +25,10 @@ import java.io.InputStreamReader;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Properties;
-import java.util.jar.JarFile;
 import java.util.regex.Pattern;
 
 import static org.apache.spark.launcher.CommandBuilderUtils.*;
diff --git a/launcher/src/main/java/org/apache/spark/launcher/LauncherProtocol.java b/launcher/src/main/java/org/apache/spark/launcher/LauncherProtocol.java
index 50f136497e..042f11cd9e 100644
--- a/launcher/src/main/java/org/apache/spark/launcher/LauncherProtocol.java
+++ b/launcher/src/main/java/org/apache/spark/launcher/LauncherProtocol.java
@@ -17,13 +17,7 @@
 
 package org.apache.spark.launcher;
 
-import java.io.Closeable;
-import java.io.IOException;
-import java.io.ObjectInputStream;
-import java.io.ObjectOutputStream;
 import java.io.Serializable;
-import java.net.Socket;
-import java.util.Map;
 
 /**
  * Message definitions for the launcher communication protocol. These messages must remain
diff --git a/mllib/src/main/scala/org/apache/spark/ml/classification/GBTClassifier.scala b/mllib/src/main/scala/org/apache/spark/ml/classification/GBTClassifier.scala
index 74bf07c3f1..e0ffbedf6c 100644
--- a/mllib/src/main/scala/org/apache/spark/ml/classification/GBTClassifier.scala
+++ b/mllib/src/main/scala/org/apache/spark/ml/classification/GBTClassifier.scala
@@ -24,7 +24,8 @@ import org.apache.spark.annotation.{Experimental, Since}
 import org.apache.spark.ml.{PredictionModel, Predictor}
 import org.apache.spark.ml.param.{Param, ParamMap}
 import org.apache.spark.ml.regression.DecisionTreeRegressionModel
-import org.apache.spark.ml.tree.{DecisionTreeModel, GBTParams, TreeClassifierParams, TreeEnsembleModel}
+import org.apache.spark.ml.tree.{DecisionTreeModel, GBTParams, TreeClassifierParams,
+  TreeEnsembleModel}
 import org.apache.spark.ml.util.{Identifiable, MetadataUtils}
 import org.apache.spark.mllib.linalg.Vector
 import org.apache.spark.mllib.regression.LabeledPoint
@@ -33,9 +34,8 @@ import org.apache.spark.mllib.tree.configuration.{Algo => OldAlgo}
 import org.apache.spark.mllib.tree.loss.{LogLoss => OldLogLoss, Loss => OldLoss}
 import org.apache.spark.mllib.tree.model.{GradientBoostedTreesModel => OldGBTModel}
 import org.apache.spark.rdd.RDD
-import org.apache.spark.sql.{DataFrame, Row}
+import org.apache.spark.sql.DataFrame
 import org.apache.spark.sql.functions._
-import org.apache.spark.sql.types.DoubleType
 
 /**
  * :: Experimental ::
diff --git a/mllib/src/main/scala/org/apache/spark/ml/evaluation/RegressionEvaluator.scala b/mllib/src/main/scala/org/apache/spark/ml/evaluation/RegressionEvaluator.scala
index adee61e297..9976d7ed43 100644
--- a/mllib/src/main/scala/org/apache/spark/ml/evaluation/RegressionEvaluator.scala
+++ b/mllib/src/main/scala/org/apache/spark/ml/evaluation/RegressionEvaluator.scala
@@ -20,7 +20,7 @@ package org.apache.spark.ml.evaluation
 import org.apache.spark.annotation.{Experimental, Since}
 import org.apache.spark.ml.param.{Param, ParamMap, ParamValidators}
 import org.apache.spark.ml.param.shared.{HasLabelCol, HasPredictionCol}
-import org.apache.spark.ml.util.{DefaultParamsReadable, DefaultParamsWritable, Identifiable, SchemaUtils}
+import org.apache.spark.ml.util.{DefaultParamsReadable, DefaultParamsWritable, Identifiable}
 import org.apache.spark.mllib.evaluation.RegressionMetrics
 import org.apache.spark.sql.{DataFrame, Row}
 import org.apache.spark.sql.functions._
diff --git a/mllib/src/main/scala/org/apache/spark/ml/feature/ElementwiseProduct.scala b/mllib/src/main/scala/org/apache/spark/ml/feature/ElementwiseProduct.scala
index 07a12df320..1e758cb775 100644
--- a/mllib/src/main/scala/org/apache/spark/ml/feature/ElementwiseProduct.scala
+++ b/mllib/src/main/scala/org/apache/spark/ml/feature/ElementwiseProduct.scala
@@ -19,7 +19,7 @@ package org.apache.spark.ml.feature
 
 import org.apache.spark.annotation.Experimental
 import org.apache.spark.ml.UnaryTransformer
-import org.apache.spark.ml.param.{Param, ParamMap}
+import org.apache.spark.ml.param.Param
 import org.apache.spark.ml.util.Identifiable
 import org.apache.spark.mllib.feature
 import org.apache.spark.mllib.linalg.{Vector, VectorUDT}
diff --git a/mllib/src/main/scala/org/apache/spark/ml/feature/StopWordsRemover.scala b/mllib/src/main/scala/org/apache/spark/ml/feature/StopWordsRemover.scala
index e53ef300f6..0d4c968633 100644
--- a/mllib/src/main/scala/org/apache/spark/ml/feature/StopWordsRemover.scala
+++ b/mllib/src/main/scala/org/apache/spark/ml/feature/StopWordsRemover.scala
@@ -24,7 +24,7 @@ import org.apache.spark.ml.param.shared.{HasInputCol, HasOutputCol}
 import org.apache.spark.ml.util._
 import org.apache.spark.sql.DataFrame
 import org.apache.spark.sql.functions.{col, udf}
-import org.apache.spark.sql.types.{ArrayType, StringType, StructField, StructType}
+import org.apache.spark.sql.types.{ArrayType, StringType, StructType}
 
 /**
  * stop words list
diff --git a/mllib/src/main/scala/org/apache/spark/ml/feature/Word2Vec.scala b/mllib/src/main/scala/org/apache/spark/ml/feature/Word2Vec.scala
index a4c3d2751f..3d3c7bdc2f 100644
--- a/mllib/src/main/scala/org/apache/spark/ml/feature/Word2Vec.scala
+++ b/mllib/src/main/scala/org/apache/spark/ml/feature/Word2Vec.scala
@@ -27,7 +27,7 @@ import org.apache.spark.ml.param.shared._
 import org.apache.spark.ml.util._
 import org.apache.spark.mllib.feature
 import org.apache.spark.mllib.linalg.{BLAS, Vector, Vectors, VectorUDT}
-import org.apache.spark.sql.{DataFrame, Row, SQLContext}
+import org.apache.spark.sql.{DataFrame, SQLContext}
 import org.apache.spark.sql.functions._
 import org.apache.spark.sql.types._
 
diff --git a/mllib/src/main/scala/org/apache/spark/ml/regression/GBTRegressor.scala b/mllib/src/main/scala/org/apache/spark/ml/regression/GBTRegressor.scala
index 07144cc7cf..9c842a6c88 100644
--- a/mllib/src/main/scala/org/apache/spark/ml/regression/GBTRegressor.scala
+++ b/mllib/src/main/scala/org/apache/spark/ml/regression/GBTRegressor.scala
@@ -23,18 +23,19 @@ import org.apache.spark.Logging
 import org.apache.spark.annotation.{Experimental, Since}
 import org.apache.spark.ml.{PredictionModel, Predictor}
 import org.apache.spark.ml.param.{Param, ParamMap}
-import org.apache.spark.ml.tree.{DecisionTreeModel, GBTParams, TreeEnsembleModel, TreeRegressorParams}
+import org.apache.spark.ml.tree.{DecisionTreeModel, GBTParams, TreeEnsembleModel,
+  TreeRegressorParams}
 import org.apache.spark.ml.util.{Identifiable, MetadataUtils}
 import org.apache.spark.mllib.linalg.Vector
 import org.apache.spark.mllib.regression.LabeledPoint
 import org.apache.spark.mllib.tree.{GradientBoostedTrees => OldGBT}
 import org.apache.spark.mllib.tree.configuration.{Algo => OldAlgo}
-import org.apache.spark.mllib.tree.loss.{AbsoluteError => OldAbsoluteError, Loss => OldLoss, SquaredError => OldSquaredError}
+import org.apache.spark.mllib.tree.loss.{AbsoluteError => OldAbsoluteError, Loss => OldLoss,
+  SquaredError => OldSquaredError}
 import org.apache.spark.mllib.tree.model.{GradientBoostedTreesModel => OldGBTModel}
 import org.apache.spark.rdd.RDD
 import org.apache.spark.sql.DataFrame
 import org.apache.spark.sql.functions._
-import org.apache.spark.sql.types.DoubleType
 
 /**
  * :: Experimental ::
diff --git a/mllib/src/main/scala/org/apache/spark/mllib/api/python/FPGrowthModelWrapper.scala b/mllib/src/main/scala/org/apache/spark/mllib/api/python/FPGrowthModelWrapper.scala
index ee933f4cfc..e6d1dceebe 100644
--- a/mllib/src/main/scala/org/apache/spark/mllib/api/python/FPGrowthModelWrapper.scala
+++ b/mllib/src/main/scala/org/apache/spark/mllib/api/python/FPGrowthModelWrapper.scala
@@ -17,8 +17,7 @@
 
 package org.apache.spark.mllib.api.python
 
-import org.apache.spark.api.java.JavaRDD
-import org.apache.spark.mllib.fpm.{FPGrowth, FPGrowthModel}
+import org.apache.spark.mllib.fpm.FPGrowthModel
 import org.apache.spark.rdd.RDD
 
 /**
diff --git a/mllib/src/main/scala/org/apache/spark/mllib/api/python/PythonMLLibAPI.scala b/mllib/src/main/scala/org/apache/spark/mllib/api/python/PythonMLLibAPI.scala
index cf17689a3a..886cd60687 100644
--- a/mllib/src/main/scala/org/apache/spark/mllib/api/python/PythonMLLibAPI.scala
+++ b/mllib/src/main/scala/org/apache/spark/mllib/api/python/PythonMLLibAPI.scala
@@ -22,13 +22,11 @@ import java.nio.{ByteBuffer, ByteOrder}
 import java.util.{ArrayList => JArrayList, List => JList, Map => JMap}
 
 import scala.collection.JavaConverters._
-import scala.collection.mutable.ArrayBuffer
 import scala.language.existentials
 import scala.reflect.ClassTag
 
 import net.razorvine.pickle._
 
-import org.apache.spark.SparkContext
 import org.apache.spark.api.java.{JavaRDD, JavaSparkContext}
 import org.apache.spark.api.python.SerDeUtil
 import org.apache.spark.mllib.classification._
@@ -51,7 +49,8 @@ import org.apache.spark.mllib.tree.{DecisionTree, GradientBoostedTrees, RandomFo
 import org.apache.spark.mllib.tree.configuration.{Algo, BoostingStrategy, Strategy}
 import org.apache.spark.mllib.tree.impurity._
 import org.apache.spark.mllib.tree.loss.Losses
-import org.apache.spark.mllib.tree.model.{DecisionTreeModel, GradientBoostedTreesModel, RandomForestModel}
+import org.apache.spark.mllib.tree.model.{DecisionTreeModel, GradientBoostedTreesModel,
+  RandomForestModel}
 import org.apache.spark.mllib.util.{LinearDataGenerator, MLUtils}
 import org.apache.spark.rdd.RDD
 import org.apache.spark.sql.{DataFrame, Row, SQLContext}
diff --git a/mllib/src/main/scala/org/apache/spark/mllib/api/python/Word2VecModelWrapper.scala b/mllib/src/main/scala/org/apache/spark/mllib/api/python/Word2VecModelWrapper.scala
index 55dfd973eb..073f03e16f 100644
--- a/mllib/src/main/scala/org/apache/spark/mllib/api/python/Word2VecModelWrapper.scala
+++ b/mllib/src/main/scala/org/apache/spark/mllib/api/python/Word2VecModelWrapper.scala
@@ -17,7 +17,7 @@
 
 package org.apache.spark.mllib.api.python
 
-import java.util.{ArrayList => JArrayList, List => JList, Map => JMap}
+import java.util.{List => JList, Map => JMap}
 
 import scala.collection.JavaConverters._
 
diff --git a/mllib/src/main/scala/org/apache/spark/mllib/classification/LogisticRegression.scala b/mllib/src/main/scala/org/apache/spark/mllib/classification/LogisticRegression.scala
index f807b5683c..c0404be019 100644
--- a/mllib/src/main/scala/org/apache/spark/mllib/classification/LogisticRegression.scala
+++ b/mllib/src/main/scala/org/apache/spark/mllib/classification/LogisticRegression.scala
@@ -27,7 +27,6 @@ import org.apache.spark.mllib.optimization._
 import org.apache.spark.mllib.pmml.PMMLExportable
 import org.apache.spark.mllib.regression._
 import org.apache.spark.mllib.util.{DataValidators, Loader, Saveable}
-import org.apache.spark.mllib.util.MLUtils.appendBias
 import org.apache.spark.rdd.RDD
 import org.apache.spark.sql.SQLContext
 import org.apache.spark.storage.StorageLevel
diff --git a/mllib/src/main/scala/org/apache/spark/mllib/clustering/GaussianMixtureModel.scala b/mllib/src/main/scala/org/apache/spark/mllib/clustering/GaussianMixtureModel.scala
index 42fe27024f..02417b1124 100644
--- a/mllib/src/main/scala/org/apache/spark/mllib/clustering/GaussianMixtureModel.scala
+++ b/mllib/src/main/scala/org/apache/spark/mllib/clustering/GaussianMixtureModel.scala
@@ -25,7 +25,7 @@ import org.json4s.jackson.JsonMethods._
 import org.apache.spark.SparkContext
 import org.apache.spark.annotation.Since
 import org.apache.spark.api.java.JavaRDD
-import org.apache.spark.mllib.linalg.{Matrices, Matrix, Vector}
+import org.apache.spark.mllib.linalg.{Matrix, Vector}
 import org.apache.spark.mllib.stat.distribution.MultivariateGaussian
 import org.apache.spark.mllib.util.{Loader, MLUtils, Saveable}
 import org.apache.spark.rdd.RDD
diff --git a/mllib/src/main/scala/org/apache/spark/mllib/evaluation/MultilabelMetrics.scala b/mllib/src/main/scala/org/apache/spark/mllib/evaluation/MultilabelMetrics.scala
index 95b2fef27a..6dd541e5c0 100644
--- a/mllib/src/main/scala/org/apache/spark/mllib/evaluation/MultilabelMetrics.scala
+++ b/mllib/src/main/scala/org/apache/spark/mllib/evaluation/MultilabelMetrics.scala
@@ -19,7 +19,6 @@ package org.apache.spark.mllib.evaluation
 
 import org.apache.spark.annotation.Since
 import org.apache.spark.rdd.RDD
-import org.apache.spark.SparkContext._
 import org.apache.spark.sql.DataFrame
 
 /**
diff --git a/mllib/src/main/scala/org/apache/spark/mllib/optimization/LBFGS.scala b/mllib/src/main/scala/org/apache/spark/mllib/optimization/LBFGS.scala
index 11179a21c8..e871165161 100644
--- a/mllib/src/main/scala/org/apache/spark/mllib/optimization/LBFGS.scala
+++ b/mllib/src/main/scala/org/apache/spark/mllib/optimization/LBFGS.scala
@@ -18,7 +18,6 @@
 package org.apache.spark.mllib.optimization
 
 import scala.collection.mutable
-import scala.collection.mutable.ArrayBuffer
 
 import breeze.linalg.{DenseVector => BDV}
 import breeze.optimize.{CachedDiffFunction, DiffFunction, LBFGS => BreezeLBFGS}
diff --git a/mllib/src/main/scala/org/apache/spark/mllib/stat/correlation/SpearmanCorrelation.scala b/mllib/src/main/scala/org/apache/spark/mllib/stat/correlation/SpearmanCorrelation.scala
index 4a6c677f06..fc684d7c5f 100644
--- a/mllib/src/main/scala/org/apache/spark/mllib/stat/correlation/SpearmanCorrelation.scala
+++ b/mllib/src/main/scala/org/apache/spark/mllib/stat/correlation/SpearmanCorrelation.scala
@@ -20,7 +20,6 @@ package org.apache.spark.mllib.stat.correlation
 import scala.collection.mutable.ArrayBuffer
 
 import org.apache.spark.Logging
-import org.apache.spark.SparkContext._
 import org.apache.spark.mllib.linalg.{Matrix, Vector, Vectors}
 import org.apache.spark.rdd.RDD
 
diff --git a/mllib/src/main/scala/org/apache/spark/mllib/tree/loss/AbsoluteError.scala b/mllib/src/main/scala/org/apache/spark/mllib/tree/loss/AbsoluteError.scala
index bab7b8c6ca..48a4e38a34 100644
--- a/mllib/src/main/scala/org/apache/spark/mllib/tree/loss/AbsoluteError.scala
+++ b/mllib/src/main/scala/org/apache/spark/mllib/tree/loss/AbsoluteError.scala
@@ -18,8 +18,6 @@
 package org.apache.spark.mllib.tree.loss
 
 import org.apache.spark.annotation.{DeveloperApi, Since}
-import org.apache.spark.mllib.regression.LabeledPoint
-import org.apache.spark.mllib.tree.model.TreeEnsembleModel
 
 
 /**
diff --git a/mllib/src/main/scala/org/apache/spark/mllib/tree/loss/LogLoss.scala b/mllib/src/main/scala/org/apache/spark/mllib/tree/loss/LogLoss.scala
index b2b4594712..b88743c0db 100644
--- a/mllib/src/main/scala/org/apache/spark/mllib/tree/loss/LogLoss.scala
+++ b/mllib/src/main/scala/org/apache/spark/mllib/tree/loss/LogLoss.scala
@@ -18,8 +18,6 @@
 package org.apache.spark.mllib.tree.loss
 
 import org.apache.spark.annotation.{DeveloperApi, Since}
-import org.apache.spark.mllib.regression.LabeledPoint
-import org.apache.spark.mllib.tree.model.TreeEnsembleModel
 import org.apache.spark.mllib.util.MLUtils
 
 
diff --git a/mllib/src/main/scala/org/apache/spark/mllib/tree/loss/SquaredError.scala b/mllib/src/main/scala/org/apache/spark/mllib/tree/loss/SquaredError.scala
index 3f7d3d38be..cb97f6fd29 100644
--- a/mllib/src/main/scala/org/apache/spark/mllib/tree/loss/SquaredError.scala
+++ b/mllib/src/main/scala/org/apache/spark/mllib/tree/loss/SquaredError.scala
@@ -18,8 +18,6 @@
 package org.apache.spark.mllib.tree.loss
 
 import org.apache.spark.annotation.{DeveloperApi, Since}
-import org.apache.spark.mllib.regression.LabeledPoint
-import org.apache.spark.mllib.tree.model.TreeEnsembleModel
 
 
 /**
diff --git a/mllib/src/main/scala/org/apache/spark/mllib/tree/model/Split.scala b/mllib/src/main/scala/org/apache/spark/mllib/tree/model/Split.scala
index 783a4acb55..5cef9d0631 100644
--- a/mllib/src/main/scala/org/apache/spark/mllib/tree/model/Split.scala
+++ b/mllib/src/main/scala/org/apache/spark/mllib/tree/model/Split.scala
@@ -18,7 +18,6 @@
 package org.apache.spark.mllib.tree.model
 
 import org.apache.spark.annotation.{DeveloperApi, Since}
-import org.apache.spark.mllib.tree.configuration.FeatureType
 import org.apache.spark.mllib.tree.configuration.FeatureType.FeatureType
 
 /**
diff --git a/mllib/src/test/java/org/apache/spark/ml/classification/JavaNaiveBayesSuite.java b/mllib/src/test/java/org/apache/spark/ml/classification/JavaNaiveBayesSuite.java
index f5f690eabd..07936eb79b 100644
--- a/mllib/src/test/java/org/apache/spark/ml/classification/JavaNaiveBayesSuite.java
+++ b/mllib/src/test/java/org/apache/spark/ml/classification/JavaNaiveBayesSuite.java
@@ -26,7 +26,6 @@ import org.junit.Before;
 import org.junit.Test;
 import static org.junit.Assert.assertEquals;
 
-import org.apache.spark.api.java.JavaRDD;
 import org.apache.spark.api.java.JavaSparkContext;
 import org.apache.spark.mllib.linalg.VectorUDT;
 import org.apache.spark.mllib.linalg.Vectors;
diff --git a/mllib/src/test/java/org/apache/spark/ml/clustering/JavaKMeansSuite.java b/mllib/src/test/java/org/apache/spark/ml/clustering/JavaKMeansSuite.java
index d09fa7fd56..cc5a4ef4c2 100644
--- a/mllib/src/test/java/org/apache/spark/ml/clustering/JavaKMeansSuite.java
+++ b/mllib/src/test/java/org/apache/spark/ml/clustering/JavaKMeansSuite.java
@@ -24,7 +24,6 @@ import java.util.List;
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
-import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
 
diff --git a/mllib/src/test/java/org/apache/spark/ml/feature/JavaBucketizerSuite.java b/mllib/src/test/java/org/apache/spark/ml/feature/JavaBucketizerSuite.java
index 8a1e5ef015..d707bdee99 100644
--- a/mllib/src/test/java/org/apache/spark/ml/feature/JavaBucketizerSuite.java
+++ b/mllib/src/test/java/org/apache/spark/ml/feature/JavaBucketizerSuite.java
@@ -24,7 +24,6 @@ import org.junit.Assert;
 import org.junit.Before;
 import org.junit.Test;
 
-import org.apache.spark.api.java.JavaRDD;
 import org.apache.spark.api.java.JavaSparkContext;
 import org.apache.spark.sql.DataFrame;
 import org.apache.spark.sql.Row;
diff --git a/mllib/src/test/java/org/apache/spark/ml/feature/JavaDCTSuite.java b/mllib/src/test/java/org/apache/spark/ml/feature/JavaDCTSuite.java
index 39da47381b..63e5c93798 100644
--- a/mllib/src/test/java/org/apache/spark/ml/feature/JavaDCTSuite.java
+++ b/mllib/src/test/java/org/apache/spark/ml/feature/JavaDCTSuite.java
@@ -25,7 +25,6 @@ import org.junit.Assert;
 import org.junit.Before;
 import org.junit.Test;
 
-import org.apache.spark.api.java.JavaRDD;
 import org.apache.spark.api.java.JavaSparkContext;
 import org.apache.spark.mllib.linalg.Vector;
 import org.apache.spark.mllib.linalg.VectorUDT;
diff --git a/mllib/src/test/java/org/apache/spark/ml/feature/JavaHashingTFSuite.java b/mllib/src/test/java/org/apache/spark/ml/feature/JavaHashingTFSuite.java
index d12332c2a0..5932017f8f 100644
--- a/mllib/src/test/java/org/apache/spark/ml/feature/JavaHashingTFSuite.java
+++ b/mllib/src/test/java/org/apache/spark/ml/feature/JavaHashingTFSuite.java
@@ -25,7 +25,6 @@ import org.junit.Assert;
 import org.junit.Before;
 import org.junit.Test;
 
-import org.apache.spark.api.java.JavaRDD;
 import org.apache.spark.api.java.JavaSparkContext;
 import org.apache.spark.mllib.linalg.Vector;
 import org.apache.spark.sql.DataFrame;
diff --git a/mllib/src/test/java/org/apache/spark/ml/feature/JavaPolynomialExpansionSuite.java b/mllib/src/test/java/org/apache/spark/ml/feature/JavaPolynomialExpansionSuite.java
index bf8eefd719..e22d117032 100644
--- a/mllib/src/test/java/org/apache/spark/ml/feature/JavaPolynomialExpansionSuite.java
+++ b/mllib/src/test/java/org/apache/spark/ml/feature/JavaPolynomialExpansionSuite.java
@@ -25,7 +25,6 @@ import org.junit.Assert;
 import org.junit.Before;
 import org.junit.Test;
 
-import org.apache.spark.api.java.JavaRDD;
 import org.apache.spark.api.java.JavaSparkContext;
 import org.apache.spark.mllib.linalg.Vector;
 import org.apache.spark.mllib.linalg.VectorUDT;
diff --git a/mllib/src/test/java/org/apache/spark/ml/feature/JavaStopWordsRemoverSuite.java b/mllib/src/test/java/org/apache/spark/ml/feature/JavaStopWordsRemoverSuite.java
index 848d9f8aa9..139d1d005a 100644
--- a/mllib/src/test/java/org/apache/spark/ml/feature/JavaStopWordsRemoverSuite.java
+++ b/mllib/src/test/java/org/apache/spark/ml/feature/JavaStopWordsRemoverSuite.java
@@ -24,7 +24,6 @@ import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
 
-import org.apache.spark.api.java.JavaRDD;
 import org.apache.spark.api.java.JavaSparkContext;
 import org.apache.spark.sql.DataFrame;
 import org.apache.spark.sql.Row;
diff --git a/mllib/src/test/java/org/apache/spark/ml/feature/JavaStringIndexerSuite.java b/mllib/src/test/java/org/apache/spark/ml/feature/JavaStringIndexerSuite.java
index b2df79ba74..153a08a4cd 100644
--- a/mllib/src/test/java/org/apache/spark/ml/feature/JavaStringIndexerSuite.java
+++ b/mllib/src/test/java/org/apache/spark/ml/feature/JavaStringIndexerSuite.java
@@ -25,7 +25,6 @@ import org.junit.Assert;
 import org.junit.Before;
 import org.junit.Test;
 
-import org.apache.spark.api.java.JavaRDD;
 import org.apache.spark.api.java.JavaSparkContext;
 import org.apache.spark.sql.DataFrame;
 import org.apache.spark.sql.Row;
diff --git a/mllib/src/test/java/org/apache/spark/ml/feature/JavaVectorAssemblerSuite.java b/mllib/src/test/java/org/apache/spark/ml/feature/JavaVectorAssemblerSuite.java
index e283777570..f8ba84ef77 100644
--- a/mllib/src/test/java/org/apache/spark/ml/feature/JavaVectorAssemblerSuite.java
+++ b/mllib/src/test/java/org/apache/spark/ml/feature/JavaVectorAssemblerSuite.java
@@ -24,7 +24,6 @@ import org.junit.Assert;
 import org.junit.Before;
 import org.junit.Test;
 
-import org.apache.spark.api.java.JavaRDD;
 import org.apache.spark.api.java.JavaSparkContext;
 import org.apache.spark.mllib.linalg.Vector;
 import org.apache.spark.mllib.linalg.VectorUDT;
diff --git a/mllib/src/test/java/org/apache/spark/ml/feature/JavaVectorSlicerSuite.java b/mllib/src/test/java/org/apache/spark/ml/feature/JavaVectorSlicerSuite.java
index 00174e6a68..786c11c412 100644
--- a/mllib/src/test/java/org/apache/spark/ml/feature/JavaVectorSlicerSuite.java
+++ b/mllib/src/test/java/org/apache/spark/ml/feature/JavaVectorSlicerSuite.java
@@ -25,7 +25,6 @@ import org.junit.Assert;
 import org.junit.Before;
 import org.junit.Test;
 
-import org.apache.spark.api.java.JavaRDD;
 import org.apache.spark.api.java.JavaSparkContext;
 import org.apache.spark.ml.attribute.Attribute;
 import org.apache.spark.ml.attribute.AttributeGroup;
diff --git a/mllib/src/test/java/org/apache/spark/ml/feature/JavaWord2VecSuite.java b/mllib/src/test/java/org/apache/spark/ml/feature/JavaWord2VecSuite.java
index 0c0c1c4d12..b292b1b06d 100644
--- a/mllib/src/test/java/org/apache/spark/ml/feature/JavaWord2VecSuite.java
+++ b/mllib/src/test/java/org/apache/spark/ml/feature/JavaWord2VecSuite.java
@@ -24,7 +24,6 @@ import org.junit.Assert;
 import org.junit.Before;
 import org.junit.Test;
 
-import org.apache.spark.api.java.JavaRDD;
 import org.apache.spark.api.java.JavaSparkContext;
 import org.apache.spark.mllib.linalg.Vector;
 import org.apache.spark.sql.DataFrame;
diff --git a/mllib/src/test/scala/org/apache/spark/ml/feature/DCTSuite.scala b/mllib/src/test/scala/org/apache/spark/ml/feature/DCTSuite.scala
index 0f2aafebaf..36cafa290f 100644
--- a/mllib/src/test/scala/org/apache/spark/ml/feature/DCTSuite.scala
+++ b/mllib/src/test/scala/org/apache/spark/ml/feature/DCTSuite.scala
@@ -25,7 +25,7 @@ import org.apache.spark.SparkFunSuite
 import org.apache.spark.ml.util.DefaultReadWriteTest
 import org.apache.spark.mllib.linalg.{Vector, Vectors}
 import org.apache.spark.mllib.util.MLlibTestSparkContext
-import org.apache.spark.sql.{DataFrame, Row}
+import org.apache.spark.sql.Row
 
 @BeanInfo
 case class DCTTestData(vec: Vector, wantedVec: Vector)
diff --git a/mllib/src/test/scala/org/apache/spark/ml/feature/StandardScalerSuite.scala b/mllib/src/test/scala/org/apache/spark/ml/feature/StandardScalerSuite.scala
index 28631cef79..8c5e47a22c 100644
--- a/mllib/src/test/scala/org/apache/spark/ml/feature/StandardScalerSuite.scala
+++ b/mllib/src/test/scala/org/apache/spark/ml/feature/StandardScalerSuite.scala
@@ -20,7 +20,6 @@ package org.apache.spark.ml.feature
 import org.apache.spark.SparkFunSuite
 import org.apache.spark.ml.param.ParamsSuite
 import org.apache.spark.ml.util.DefaultReadWriteTest
-import org.apache.spark.mllib.feature
 import org.apache.spark.mllib.linalg.{Vector, Vectors}
 import org.apache.spark.mllib.util.MLlibTestSparkContext
 import org.apache.spark.mllib.util.TestingUtils._
diff --git a/mllib/src/test/scala/org/apache/spark/ml/feature/Word2VecSuite.scala b/mllib/src/test/scala/org/apache/spark/ml/feature/Word2VecSuite.scala
index 1671fb6f3a..80c177b8d3 100644
--- a/mllib/src/test/scala/org/apache/spark/ml/feature/Word2VecSuite.scala
+++ b/mllib/src/test/scala/org/apache/spark/ml/feature/Word2VecSuite.scala
@@ -24,7 +24,7 @@ import org.apache.spark.mllib.feature.{Word2VecModel => OldWord2VecModel}
 import org.apache.spark.mllib.linalg.{Vector, Vectors}
 import org.apache.spark.mllib.util.MLlibTestSparkContext
 import org.apache.spark.mllib.util.TestingUtils._
-import org.apache.spark.sql.{Row, SQLContext}
+import org.apache.spark.sql.Row
 
 class Word2VecSuite extends SparkFunSuite with MLlibTestSparkContext with DefaultReadWriteTest {
 
diff --git a/mllib/src/test/scala/org/apache/spark/mllib/feature/Word2VecSuite.scala b/mllib/src/test/scala/org/apache/spark/mllib/feature/Word2VecSuite.scala
index e74ecc16ee..4fcf417d5f 100644
--- a/mllib/src/test/scala/org/apache/spark/mllib/feature/Word2VecSuite.scala
+++ b/mllib/src/test/scala/org/apache/spark/mllib/feature/Word2VecSuite.scala
@@ -19,7 +19,6 @@ package org.apache.spark.mllib.feature
 
 import org.apache.spark.SparkFunSuite
 import org.apache.spark.mllib.util.MLlibTestSparkContext
-import org.apache.spark.mllib.util.TestingUtils._
 import org.apache.spark.util.Utils
 
 class Word2VecSuite extends SparkFunSuite with MLlibTestSparkContext {
diff --git a/mllib/src/test/scala/org/apache/spark/mllib/random/RandomRDDsSuite.scala b/mllib/src/test/scala/org/apache/spark/mllib/random/RandomRDDsSuite.scala
index 0b4c7eb302..f464d25c3f 100644
--- a/mllib/src/test/scala/org/apache/spark/mllib/random/RandomRDDsSuite.scala
+++ b/mllib/src/test/scala/org/apache/spark/mllib/random/RandomRDDsSuite.scala
@@ -19,7 +19,6 @@ package org.apache.spark.mllib.random
 
 import scala.collection.mutable.ArrayBuffer
 
-import org.apache.spark.SparkContext._
 import org.apache.spark.SparkFunSuite
 import org.apache.spark.mllib.linalg.Vector
 import org.apache.spark.mllib.rdd.{RandomRDD, RandomRDDPartition}
diff --git a/repl/scala-2.11/src/main/scala/org/apache/spark/repl/Main.scala b/repl/scala-2.11/src/main/scala/org/apache/spark/repl/Main.scala
index 1ae4182947..999e7ad3cc 100644
--- a/repl/scala-2.11/src/main/scala/org/apache/spark/repl/Main.scala
+++ b/repl/scala-2.11/src/main/scala/org/apache/spark/repl/Main.scala
@@ -21,8 +21,8 @@ import java.io.File
 
 import scala.tools.nsc.GenericRunnerSettings
 
-import org.apache.spark.util.Utils
 import org.apache.spark._
+import org.apache.spark.util.Utils
 import org.apache.spark.sql.SQLContext
 
 object Main extends Logging {
diff --git a/repl/scala-2.11/src/main/scala/org/apache/spark/repl/SparkILoop.scala b/repl/scala-2.11/src/main/scala/org/apache/spark/repl/SparkILoop.scala
index e91139fb29..7ed6d3b1f9 100644
--- a/repl/scala-2.11/src/main/scala/org/apache/spark/repl/SparkILoop.scala
+++ b/repl/scala-2.11/src/main/scala/org/apache/spark/repl/SparkILoop.scala
@@ -17,10 +17,10 @@
 
 package org.apache.spark.repl
 
-import java.io.{BufferedReader, FileReader}
+import java.io.BufferedReader
 
 import Predef.{println => _, _}
-import scala.util.Properties.{jdkHome, javaVersion, versionString, javaVmName}
+import scala.util.Properties.{javaVersion, versionString, javaVmName}
 
 import scala.tools.nsc.interpreter.{JPrintWriter, ILoop}
 import scala.tools.nsc.Settings
diff --git a/repl/scala-2.11/src/test/scala/org/apache/spark/repl/ReplSuite.scala b/repl/scala-2.11/src/test/scala/org/apache/spark/repl/ReplSuite.scala
index b9ed79da42..239096be79 100644
--- a/repl/scala-2.11/src/test/scala/org/apache/spark/repl/ReplSuite.scala
+++ b/repl/scala-2.11/src/test/scala/org/apache/spark/repl/ReplSuite.scala
@@ -21,7 +21,6 @@ import java.io._
 import java.net.URLClassLoader
 
 import scala.collection.mutable.ArrayBuffer
-import scala.concurrent.duration._
 
 import org.apache.commons.lang3.StringEscapeUtils
 import org.apache.spark.{SparkContext, SparkFunSuite}
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/Row.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/Row.scala
index b14c66cc5a..f108264861 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/Row.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/Row.scala
@@ -20,7 +20,6 @@ package org.apache.spark.sql
 import scala.collection.JavaConverters._
 import scala.util.hashing.MurmurHash3
 
-import org.apache.spark.sql.catalyst.InternalRow
 import org.apache.spark.sql.catalyst.expressions.GenericRow
 import org.apache.spark.sql.types.StructType
 
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/encoders/package.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/encoders/package.scala
index 9e283f5eb6..03708fb7af 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/encoders/package.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/encoders/package.scala
@@ -18,7 +18,6 @@
 package org.apache.spark.sql.catalyst
 
 import org.apache.spark.sql.Encoder
-import org.apache.spark.sql.catalyst.expressions.AttributeReference
 
 package object encoders {
   /**
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/ExpectsInputTypes.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/ExpectsInputTypes.scala
index c7be8e886c..b3dfac806f 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/ExpectsInputTypes.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/ExpectsInputTypes.scala
@@ -17,7 +17,6 @@
 
 package org.apache.spark.sql.catalyst.expressions
 
-import org.apache.spark.sql.catalyst.analysis.HiveTypeCoercion.ImplicitTypeCasts
 import org.apache.spark.sql.catalyst.analysis.TypeCheckResult
 import org.apache.spark.sql.types.AbstractDataType
 
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/codegen/GenerateMutableProjection.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/codegen/GenerateMutableProjection.scala
index 9abe92b1e7..7f840890f8 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/codegen/GenerateMutableProjection.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/codegen/GenerateMutableProjection.scala
@@ -19,7 +19,6 @@ package org.apache.spark.sql.catalyst.expressions.codegen
 
 import org.apache.spark.sql.catalyst.expressions._
 import org.apache.spark.sql.catalyst.expressions.aggregate.NoOp
-import org.apache.spark.sql.types.DecimalType
 
 // MutableProjection is not accessible in Java
 abstract class BaseMutableProjection extends MutableProjection
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/QueryPlan.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/QueryPlan.scala
index a74b288cb2..3ff37fffbd 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/QueryPlan.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/QueryPlan.scala
@@ -18,7 +18,6 @@
 package org.apache.spark.sql.catalyst.plans
 
 import org.apache.spark.sql.catalyst.expressions._
-import org.apache.spark.sql.catalyst.plans.logical.SubqueryAlias
 import org.apache.spark.sql.catalyst.trees.TreeNode
 import org.apache.spark.sql.types.{DataType, StructType}
 
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/LocalRelation.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/LocalRelation.scala
index f9f1f88cec..5813b74c77 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/LocalRelation.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/LocalRelation.scala
@@ -19,7 +19,7 @@ package org.apache.spark.sql.catalyst.plans.logical
 
 import org.apache.spark.sql.Row
 import org.apache.spark.sql.catalyst.{analysis, CatalystTypeConverters, InternalRow}
-import org.apache.spark.sql.catalyst.expressions.{Attribute, AttributeSet}
+import org.apache.spark.sql.catalyst.expressions.Attribute
 import org.apache.spark.sql.types.{StructField, StructType}
 
 object LocalRelation {
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/physical/partitioning.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/physical/partitioning.scala
index 45e2841ec9..be9f1ffa22 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/physical/partitioning.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/physical/partitioning.scala
@@ -17,7 +17,6 @@
 
 package org.apache.spark.sql.catalyst.plans.physical
 
-import org.apache.spark.sql.catalyst.InternalRow
 import org.apache.spark.sql.catalyst.expressions._
 import org.apache.spark.sql.types.{DataType, IntegerType}
 
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/trees/TreeNode.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/trees/TreeNode.scala
index e46ce1cee7..2d0bf6b375 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/trees/TreeNode.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/trees/TreeNode.scala
@@ -28,15 +28,12 @@ import org.json4s.jackson.JsonMethods._
 
 import org.apache.spark.SparkContext
 import org.apache.spark.rdd.{EmptyRDD, RDD}
-import org.apache.spark.sql.catalyst.{ScalaReflectionLock, TableIdentifier}
 import org.apache.spark.sql.catalyst.ScalaReflection._
+import org.apache.spark.sql.catalyst.ScalaReflectionLock
 import org.apache.spark.sql.catalyst.errors._
 import org.apache.spark.sql.catalyst.expressions._
-import org.apache.spark.sql.catalyst.plans.logical.Statistics
-import org.apache.spark.sql.catalyst.util.DateTimeUtils
 import org.apache.spark.sql.types._
 import org.apache.spark.storage.StorageLevel
-import org.apache.spark.unsafe.types.{CalendarInterval, UTF8String}
 import org.apache.spark.util.Utils
 
 /** Used by [[TreeNode.getNodeNumbered]] when traversing the tree for a given number */
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/ScalaReflectionSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/ScalaReflectionSuite.scala
index a32f5b70a0..5fe09b1a4d 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/ScalaReflectionSuite.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/ScalaReflectionSuite.scala
@@ -17,7 +17,6 @@
 
 package org.apache.spark.sql.catalyst
 
-import java.math.BigInteger
 import java.sql.{Date, Timestamp}
 
 import org.apache.spark.SparkFunSuite
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/encoders/RowEncoderSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/encoders/RowEncoderSuite.scala
index 932511134c..f119c6f4f7 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/encoders/RowEncoderSuite.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/encoders/RowEncoderSuite.scala
@@ -23,7 +23,6 @@ import org.apache.spark.SparkFunSuite
 import org.apache.spark.sql.{RandomDataGenerator, Row}
 import org.apache.spark.sql.catalyst.util.{ArrayData, GenericArrayData}
 import org.apache.spark.sql.types._
-import org.apache.spark.unsafe.types.UTF8String
 
 @SQLUserDefinedType(udt = classOf[ExamplePointUDT])
 class ExamplePoint(val x: Double, val y: Double) extends Serializable {
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/LiteralGenerator.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/LiteralGenerator.scala
index d9c91415e2..032aec0178 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/LiteralGenerator.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/LiteralGenerator.scala
@@ -20,8 +20,6 @@ package org.apache.spark.sql.catalyst.expressions
 import java.sql.{Date, Timestamp}
 
 import org.scalacheck.{Arbitrary, Gen}
-import org.scalatest.Matchers
-import org.scalatest.prop.GeneratorDrivenPropertyChecks
 
 import org.apache.spark.sql.types._
 import org.apache.spark.unsafe.types.CalendarInterval
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/aggregate/HyperLogLogPlusPlusSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/aggregate/HyperLogLogPlusPlusSuite.scala
index 83838294a9..0dbfb01e88 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/aggregate/HyperLogLogPlusPlusSuite.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/aggregate/HyperLogLogPlusPlusSuite.scala
@@ -21,8 +21,6 @@ import java.util.Random
 
 import scala.collection.mutable
 
-import org.scalatest.Assertions._
-
 import org.apache.spark.SparkFunSuite
 import org.apache.spark.sql.catalyst.expressions.{BoundReference, MutableRow, SpecificMutableRow}
 import org.apache.spark.sql.types.{DataType, IntegerType}
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/AggregateOptimizeSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/AggregateOptimizeSuite.scala
index a4a12c0d62..e458eb8a1d 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/AggregateOptimizeSuite.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/AggregateOptimizeSuite.scala
@@ -21,7 +21,7 @@ import org.apache.spark.sql.catalyst.dsl.expressions._
 import org.apache.spark.sql.catalyst.dsl.plans._
 import org.apache.spark.sql.catalyst.expressions.Literal
 import org.apache.spark.sql.catalyst.plans.PlanTest
-import org.apache.spark.sql.catalyst.plans.logical.{Aggregate, Distinct, LocalRelation, LogicalPlan}
+import org.apache.spark.sql.catalyst.plans.logical.{LocalRelation, LogicalPlan}
 import org.apache.spark.sql.catalyst.rules.RuleExecutor
 
 class AggregateOptimizeSuite extends PlanTest {
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/OptimizeInSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/OptimizeInSuite.scala
index 17255ecfe8..0e43ce034f 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/OptimizeInSuite.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/OptimizeInSuite.scala
@@ -17,8 +17,6 @@
 
 package org.apache.spark.sql.catalyst.optimizer
 
-import scala.collection.immutable.HashSet
-
 import org.apache.spark.sql.catalyst.analysis.{EliminateSubqueryAliases, UnresolvedAttribute}
 import org.apache.spark.sql.catalyst.dsl.expressions._
 import org.apache.spark.sql.catalyst.dsl.plans._
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/plans/LogicalPlanSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/plans/LogicalPlanSuite.scala
index 455a3810c7..faef9ed274 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/plans/LogicalPlanSuite.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/plans/LogicalPlanSuite.scala
@@ -18,9 +18,7 @@
 package org.apache.spark.sql.catalyst.plans
 
 import org.apache.spark.SparkFunSuite
-import org.apache.spark.sql.catalyst.expressions._
 import org.apache.spark.sql.catalyst.plans.logical._
-import org.apache.spark.sql.catalyst.util._
 
 /**
  * This suite is used to test [[LogicalPlan]]'s `resolveOperators` and make sure it can correctly
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/plans/SameResultSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/plans/SameResultSuite.scala
index fb4f34d059..37941cf34e 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/plans/SameResultSuite.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/plans/SameResultSuite.scala
@@ -20,7 +20,6 @@ package org.apache.spark.sql.catalyst.plans
 import org.apache.spark.SparkFunSuite
 import org.apache.spark.sql.catalyst.dsl.expressions._
 import org.apache.spark.sql.catalyst.dsl.plans._
-import org.apache.spark.sql.catalyst.expressions.{AttributeReference, ExprId}
 import org.apache.spark.sql.catalyst.plans.logical.{LocalRelation, LogicalPlan}
 import org.apache.spark.sql.catalyst.util._
 
diff --git a/sql/core/src/main/java/org/apache/spark/sql/execution/UnsafeFixedWidthAggregationMap.java b/sql/core/src/main/java/org/apache/spark/sql/execution/UnsafeFixedWidthAggregationMap.java
index 2e84178d69..57e8218f3b 100644
--- a/sql/core/src/main/java/org/apache/spark/sql/execution/UnsafeFixedWidthAggregationMap.java
+++ b/sql/core/src/main/java/org/apache/spark/sql/execution/UnsafeFixedWidthAggregationMap.java
@@ -29,7 +29,6 @@ import org.apache.spark.sql.types.StructType;
 import org.apache.spark.unsafe.KVIterator;
 import org.apache.spark.unsafe.Platform;
 import org.apache.spark.unsafe.map.BytesToBytesMap;
-import org.apache.spark.unsafe.memory.MemoryLocation;
 
 /**
  * Unsafe-based HashMap for performing aggregations where the aggregated values are fixed-width.
diff --git a/sql/core/src/main/java/org/apache/spark/sql/execution/datasources/parquet/VectorizedPlainValuesReader.java b/sql/core/src/main/java/org/apache/spark/sql/execution/datasources/parquet/VectorizedPlainValuesReader.java
index ee9a7a221b..2672e0453b 100644
--- a/sql/core/src/main/java/org/apache/spark/sql/execution/datasources/parquet/VectorizedPlainValuesReader.java
+++ b/sql/core/src/main/java/org/apache/spark/sql/execution/datasources/parquet/VectorizedPlainValuesReader.java
@@ -18,11 +18,9 @@ package org.apache.spark.sql.execution.datasources.parquet;
 
 import java.io.IOException;
 
-import org.apache.spark.sql.Column;
 import org.apache.spark.sql.execution.vectorized.ColumnVector;
 import org.apache.spark.unsafe.Platform;
 
-import org.apache.commons.lang.NotImplementedException;
 import org.apache.parquet.column.values.ValuesReader;
 import org.apache.parquet.io.api.Binary;
 
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/DataFrame.scala b/sql/core/src/main/scala/org/apache/spark/sql/DataFrame.scala
index 5f5b7f4c19..844bc0fdd1 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/DataFrame.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/DataFrame.scala
@@ -20,7 +20,6 @@ package org.apache.spark.sql
 import java.io.CharArrayWriter
 
 import scala.language.implicitConversions
-import scala.reflect.ClassTag
 import scala.reflect.runtime.universe.TypeTag
 
 import com.fasterxml.jackson.core.JsonFactory
@@ -37,7 +36,8 @@ import org.apache.spark.sql.catalyst.optimizer.CombineUnions
 import org.apache.spark.sql.catalyst.plans._
 import org.apache.spark.sql.catalyst.plans.logical._
 import org.apache.spark.sql.catalyst.util.usePrettyExpression
-import org.apache.spark.sql.execution.{ExplainCommand, FileRelation, LogicalRDD, Queryable, QueryExecution, SQLExecution}
+import org.apache.spark.sql.execution.{ExplainCommand, FileRelation, LogicalRDD, Queryable,
+  QueryExecution, SQLExecution}
 import org.apache.spark.sql.execution.datasources.{CreateTableUsingAsSelect, LogicalRelation}
 import org.apache.spark.sql.execution.datasources.json.JacksonGenerator
 import org.apache.spark.sql.execution.python.EvaluatePython
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/GroupedDataset.scala b/sql/core/src/main/scala/org/apache/spark/sql/GroupedDataset.scala
index 53cb8eb524..cd8ed472ec 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/GroupedDataset.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/GroupedDataset.scala
@@ -25,7 +25,6 @@ import org.apache.spark.sql.catalyst.encoders.{encoderFor, ExpressionEncoder, Ou
 import org.apache.spark.sql.catalyst.expressions.{Alias, Attribute, CreateStruct}
 import org.apache.spark.sql.catalyst.plans.logical._
 import org.apache.spark.sql.execution.QueryExecution
-import org.apache.spark.sql.expressions.Aggregator
 
 /**
  * :: Experimental ::
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/api/r/SQLUtils.scala b/sql/core/src/main/scala/org/apache/spark/sql/api/r/SQLUtils.scala
index d8af799d89..22ded7a4bf 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/api/r/SQLUtils.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/api/r/SQLUtils.scala
@@ -24,8 +24,8 @@ import scala.util.matching.Regex
 import org.apache.spark.api.java.{JavaRDD, JavaSparkContext}
 import org.apache.spark.api.r.SerDe
 import org.apache.spark.rdd.RDD
-import org.apache.spark.sql.{Column, DataFrame, GroupedData, Row, SaveMode, SQLContext}
-import org.apache.spark.sql.catalyst.expressions.{Alias, Expression, GenericRowWithSchema, NamedExpression}
+import org.apache.spark.sql.{DataFrame, Row, SaveMode, SQLContext}
+import org.apache.spark.sql.catalyst.expressions.GenericRowWithSchema
 import org.apache.spark.sql.types._
 
 private[r] object SQLUtils {
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/SparkQl.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/SparkQl.scala
index 4174e27e9c..8c41d80bf1 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/SparkQl.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/SparkQl.scala
@@ -21,7 +21,6 @@ import org.apache.spark.sql.catalyst.{CatalystQl, TableIdentifier}
 import org.apache.spark.sql.catalyst.analysis.UnresolvedRelation
 import org.apache.spark.sql.catalyst.parser.{ASTNode, ParserConf, SimpleParserConf}
 import org.apache.spark.sql.catalyst.plans.logical.{LogicalPlan, OneRowRelation}
-import org.apache.spark.sql.catalyst.plans.logical
 import org.apache.spark.sql.execution.datasources._
 import org.apache.spark.sql.types.StructType
 
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/aggregate/TungstenAggregationIterator.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/aggregate/TungstenAggregationIterator.scala
index c4f6594835..5e1ea90cd4 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/aggregate/TungstenAggregationIterator.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/aggregate/TungstenAggregationIterator.scala
@@ -17,7 +17,7 @@
 
 package org.apache.spark.sql.execution.aggregate
 
-import org.apache.spark.{InternalAccumulator, Logging, TaskContext}
+import org.apache.spark.{Logging, TaskContext}
 import org.apache.spark.sql.catalyst.InternalRow
 import org.apache.spark.sql.catalyst.expressions._
 import org.apache.spark.sql.catalyst.expressions.aggregate._
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/WriterContainer.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/WriterContainer.scala
index 097e9c912b..3653aca994 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/WriterContainer.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/WriterContainer.scala
@@ -26,7 +26,6 @@ import org.apache.hadoop.mapreduce.task.TaskAttemptContextImpl
 
 import org.apache.spark._
 import org.apache.spark.mapred.SparkHadoopMapRedUtil
-import org.apache.spark.sql._
 import org.apache.spark.sql.catalyst.expressions._
 import org.apache.spark.sql.catalyst.plans.physical.HashPartitioning
 import org.apache.spark.sql.catalyst.InternalRow
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/json/JSONRelation.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/json/JSONRelation.scala
index 28136911fe..2eba52f326 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/json/JSONRelation.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/json/JSONRelation.scala
@@ -23,7 +23,6 @@ import com.fasterxml.jackson.core.JsonFactory
 import com.google.common.base.Objects
 import org.apache.hadoop.fs.{FileStatus, Path}
 import org.apache.hadoop.io.{LongWritable, NullWritable, Text}
-import org.apache.hadoop.io.SequenceFile.CompressionType
 import org.apache.hadoop.mapred.{JobConf, TextInputFormat}
 import org.apache.hadoop.mapreduce.{Job, RecordWriter, TaskAttemptContext}
 import org.apache.hadoop.mapreduce.lib.input.FileInputFormat
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/json/JacksonGenerator.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/json/JacksonGenerator.scala
index 078e1cbec5..8b920ecafa 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/json/JacksonGenerator.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/json/JacksonGenerator.scala
@@ -17,11 +17,8 @@
 
 package org.apache.spark.sql.execution.datasources.json
 
-import scala.collection.Map
-
 import com.fasterxml.jackson.core._
 
-import org.apache.spark.sql.Row
 import org.apache.spark.sql.catalyst.InternalRow
 import org.apache.spark.sql.catalyst.util.{ArrayData, DateTimeUtils, MapData}
 import org.apache.spark.sql.types._
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/parquet/CatalystReadSupport.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/parquet/CatalystReadSupport.scala
index c3b7483e80..e34309bab1 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/parquet/CatalystReadSupport.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/parquet/CatalystReadSupport.scala
@@ -29,7 +29,6 @@ import org.apache.parquet.schema._
 import org.apache.parquet.schema.Type.Repetition
 
 import org.apache.spark.Logging
-import org.apache.spark.deploy.SparkHadoopUtil
 import org.apache.spark.sql.catalyst.InternalRow
 import org.apache.spark.sql.types._
 
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/joins/HashSemiJoin.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/joins/HashSemiJoin.scala
index 3eed6e3e11..813ec02425 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/joins/HashSemiJoin.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/joins/HashSemiJoin.scala
@@ -19,7 +19,6 @@ package org.apache.spark.sql.execution.joins
 
 import org.apache.spark.sql.catalyst.InternalRow
 import org.apache.spark.sql.catalyst.expressions._
-import org.apache.spark.sql.catalyst.plans.physical.BroadcastMode
 import org.apache.spark.sql.execution.SparkPlan
 import org.apache.spark.sql.execution.metric.LongSQLMetric
 
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/joins/HashedRelation.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/joins/HashedRelation.scala
index 606269bf25..9a3cdaf697 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/joins/HashedRelation.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/joins/HashedRelation.scala
@@ -26,7 +26,7 @@ import org.apache.spark.memory.{StaticMemoryManager, TaskMemoryManager}
 import org.apache.spark.sql.catalyst.InternalRow
 import org.apache.spark.sql.catalyst.expressions._
 import org.apache.spark.sql.catalyst.plans.physical.BroadcastMode
-import org.apache.spark.sql.execution.{SparkPlan, SparkSqlSerializer}
+import org.apache.spark.sql.execution.SparkSqlSerializer
 import org.apache.spark.sql.execution.local.LocalNode
 import org.apache.spark.unsafe.Platform
 import org.apache.spark.unsafe.map.BytesToBytesMap
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/limit.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/limit.scala
index 45175d36d5..5a7516b7f9 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/limit.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/limit.scala
@@ -24,7 +24,6 @@ import org.apache.spark.sql.catalyst.expressions._
 import org.apache.spark.sql.catalyst.expressions.codegen.{CodegenContext, ExprCode, LazilyGeneratedOrdering}
 import org.apache.spark.sql.catalyst.plans.physical._
 import org.apache.spark.sql.execution.exchange.ShuffleExchange
-import org.apache.spark.sql.execution.metric.SQLMetrics
 
 
 /**
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/local/BinaryHashJoinNode.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/local/BinaryHashJoinNode.scala
index 8f063e24fb..97f9358016 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/local/BinaryHashJoinNode.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/local/BinaryHashJoinNode.scala
@@ -17,7 +17,6 @@
 
 package org.apache.spark.sql.execution.local
 
-import org.apache.spark.sql.catalyst.InternalRow
 import org.apache.spark.sql.catalyst.expressions._
 import org.apache.spark.sql.execution.joins.{BuildLeft, BuildRight, BuildSide, HashedRelation}
 import org.apache.spark.sql.internal.SQLConf
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/local/BroadcastHashJoinNode.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/local/BroadcastHashJoinNode.scala
index 9ffa272d21..779f4833fa 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/local/BroadcastHashJoinNode.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/local/BroadcastHashJoinNode.scala
@@ -18,7 +18,6 @@
 package org.apache.spark.sql.execution.local
 
 import org.apache.spark.broadcast.Broadcast
-import org.apache.spark.sql.catalyst.InternalRow
 import org.apache.spark.sql.catalyst.expressions._
 import org.apache.spark.sql.execution.joins.{BuildLeft, BuildRight, BuildSide, HashedRelation}
 import org.apache.spark.sql.internal.SQLConf
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/CompositeOffset.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/CompositeOffset.scala
index d2cb20ef8b..59a52a3d59 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/CompositeOffset.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/CompositeOffset.scala
@@ -17,8 +17,6 @@
 
 package org.apache.spark.sql.execution.streaming
 
-import scala.util.Try
-
 /**
  * An ordered collection of offsets, used to track the progress of processing data from one or more
  * [[Source]]s that are present in a streaming query. This is similar to simplified, single-instance
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/expressions/WindowSpec.scala b/sql/core/src/main/scala/org/apache/spark/sql/expressions/WindowSpec.scala
index 3921147857..9e9c58cb66 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/expressions/WindowSpec.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/expressions/WindowSpec.scala
@@ -20,7 +20,6 @@ package org.apache.spark.sql.expressions
 import org.apache.spark.annotation.Experimental
 import org.apache.spark.sql.{catalyst, Column}
 import org.apache.spark.sql.catalyst.expressions._
-import org.apache.spark.sql.catalyst.expressions.aggregate._
 
 /**
  * :: Experimental ::
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/UserDefinedTypeSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/UserDefinedTypeSuite.scala
index 6800a8ddf6..9081bc722a 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/UserDefinedTypeSuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/UserDefinedTypeSuite.scala
@@ -26,7 +26,6 @@ import org.apache.spark.sql.execution.datasources.parquet.ParquetTest
 import org.apache.spark.sql.functions._
 import org.apache.spark.sql.test.SharedSQLContext
 import org.apache.spark.sql.types._
-import org.apache.spark.util.collection.OpenHashSet
 
 @SQLUserDefinedType(udt = classOf[MyDenseVectorUDT])
 private[sql] class MyDenseVector(val data: Array[Double]) extends Serializable {
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/execution/ReferenceSort.scala b/sql/core/src/test/scala/org/apache/spark/sql/execution/ReferenceSort.scala
index 273937fa8c..2963a856d1 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/execution/ReferenceSort.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/execution/ReferenceSort.scala
@@ -17,7 +17,7 @@
 
 package org.apache.spark.sql.execution
 
-import org.apache.spark.{InternalAccumulator, TaskContext}
+import org.apache.spark.TaskContext
 import org.apache.spark.rdd.RDD
 import org.apache.spark.sql.catalyst.InternalRow
 import org.apache.spark.sql.catalyst.errors._
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/execution/SQLExecutionSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/execution/SQLExecutionSuite.scala
index 63639681ef..824d89e3b2 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/execution/SQLExecutionSuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/execution/SQLExecutionSuite.scala
@@ -19,8 +19,6 @@ package org.apache.spark.sql.execution
 
 import java.util.Properties
 
-import scala.collection.parallel.CompositeThrowable
-
 import org.apache.spark.{SparkConf, SparkContext, SparkFunSuite}
 import org.apache.spark.sql.SQLContext
 
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/execution/SparkPlanTest.scala b/sql/core/src/test/scala/org/apache/spark/sql/execution/SparkPlanTest.scala
index 8549a6a0f6..aa928cfc80 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/execution/SparkPlanTest.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/execution/SparkPlanTest.scala
@@ -18,11 +18,10 @@
 package org.apache.spark.sql.execution
 
 import scala.language.implicitConversions
-import scala.reflect.runtime.universe.TypeTag
 import scala.util.control.NonFatal
 
 import org.apache.spark.SparkFunSuite
-import org.apache.spark.sql.{DataFrame, DataFrameHolder, Row, SQLContext}
+import org.apache.spark.sql.{DataFrame, Row, SQLContext}
 import org.apache.spark.sql.catalyst.analysis.UnresolvedAttribute
 import org.apache.spark.sql.test.SQLTestUtils
 
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/execution/UnsafeFixedWidthAggregationMapSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/execution/UnsafeFixedWidthAggregationMapSuite.scala
index c7df8b51e2..4dc7d3461c 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/execution/UnsafeFixedWidthAggregationMapSuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/execution/UnsafeFixedWidthAggregationMapSuite.scala
@@ -26,7 +26,7 @@ import org.scalatest.Matchers
 import org.apache.spark.{SparkConf, SparkFunSuite, TaskContext, TaskContextImpl}
 import org.apache.spark.memory.{TaskMemoryManager, TestMemoryManager}
 import org.apache.spark.sql.catalyst.InternalRow
-import org.apache.spark.sql.catalyst.expressions.{UnsafeProjection, UnsafeRow}
+import org.apache.spark.sql.catalyst.expressions.UnsafeRow
 import org.apache.spark.sql.test.SharedSQLContext
 import org.apache.spark.sql.types._
 import org.apache.spark.unsafe.types.UTF8String
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/execution/UnsafeRowSerializerSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/execution/UnsafeRowSerializerSuite.scala
index 7438e11ef7..50bdcd6c2c 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/execution/UnsafeRowSerializerSuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/execution/UnsafeRowSerializerSuite.scala
@@ -20,7 +20,6 @@ package org.apache.spark.sql.execution
 import java.io.{ByteArrayInputStream, ByteArrayOutputStream, File}
 
 import org.apache.spark._
-import org.apache.spark.executor.ShuffleWriteMetrics
 import org.apache.spark.memory.TaskMemoryManager
 import org.apache.spark.rdd.RDD
 import org.apache.spark.sql.Row
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/execution/columnar/PartitionBatchPruningSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/execution/columnar/PartitionBatchPruningSuite.scala
index d19fec6140..4f185ed283 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/execution/columnar/PartitionBatchPruningSuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/execution/columnar/PartitionBatchPruningSuite.scala
@@ -20,7 +20,6 @@ package org.apache.spark.sql.execution.columnar
 import org.scalatest.BeforeAndAfterEach
 
 import org.apache.spark.SparkFunSuite
-import org.apache.spark.sql._
 import org.apache.spark.sql.internal.SQLConf
 import org.apache.spark.sql.test.SharedSQLContext
 import org.apache.spark.sql.test.SQLTestData._
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetEncodingSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetEncodingSuite.scala
index 281a2cffa8..29318d8b56 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetEncodingSuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetEncodingSuite.scala
@@ -16,7 +16,6 @@
  */
 package org.apache.spark.sql.execution.datasources.parquet
 
-import org.apache.spark.sql.execution.vectorized.ColumnVectorUtils
 import org.apache.spark.sql.test.SharedSQLContext
 
 // TODO: this needs a lot more testing but it's currently not easy to test with the parquet
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/execution/local/HashJoinNodeSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/execution/local/HashJoinNodeSuite.scala
index 268f2aac87..74142ea598 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/execution/local/HashJoinNodeSuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/execution/local/HashJoinNodeSuite.scala
@@ -21,7 +21,7 @@ import org.mockito.Mockito.{mock, when}
 
 import org.apache.spark.broadcast.TorrentBroadcast
 import org.apache.spark.sql.catalyst.dsl.expressions._
-import org.apache.spark.sql.catalyst.expressions.{Expression, InterpretedMutableProjection, UnsafeProjection}
+import org.apache.spark.sql.catalyst.expressions.{Expression, UnsafeProjection}
 import org.apache.spark.sql.execution.joins.{BuildLeft, BuildRight, BuildSide, HashedRelation}
 import org.apache.spark.sql.internal.SQLConf
 
diff --git a/sql/hive-thriftserver/src/main/scala/org/apache/spark/sql/hive/thriftserver/SparkSQLCLIDriver.scala b/sql/hive-thriftserver/src/main/scala/org/apache/spark/sql/hive/thriftserver/SparkSQLCLIDriver.scala
index fb31119a9e..79cf7e8378 100644
--- a/sql/hive-thriftserver/src/main/scala/org/apache/spark/sql/hive/thriftserver/SparkSQLCLIDriver.scala
+++ b/sql/hive-thriftserver/src/main/scala/org/apache/spark/sql/hive/thriftserver/SparkSQLCLIDriver.scala
@@ -32,14 +32,15 @@ import org.apache.hadoop.hive.common.{HiveInterruptCallback, HiveInterruptUtils}
 import org.apache.hadoop.hive.conf.HiveConf
 import org.apache.hadoop.hive.ql.Driver
 import org.apache.hadoop.hive.ql.exec.Utilities
-import org.apache.hadoop.hive.ql.processors.{AddResourceProcessor, CommandProcessor, CommandProcessorFactory, SetProcessor}
+import org.apache.hadoop.hive.ql.processors.{AddResourceProcessor, CommandProcessor,
+  CommandProcessorFactory, SetProcessor}
 import org.apache.hadoop.hive.ql.session.SessionState
 import org.apache.thrift.transport.TSocket
 
 import org.apache.spark.Logging
 import org.apache.spark.sql.AnalysisException
 import org.apache.spark.sql.hive.HiveContext
-import org.apache.spark.util.{ShutdownHookManager, Utils}
+import org.apache.spark.util.ShutdownHookManager
 
 /**
  * This code doesn't support remote connections in Hive 1.2+, as the underlying CliDriver
diff --git a/sql/hive-thriftserver/src/main/scala/org/apache/spark/sql/hive/thriftserver/SparkSQLDriver.scala b/sql/hive-thriftserver/src/main/scala/org/apache/spark/sql/hive/thriftserver/SparkSQLDriver.scala
index 4278aa30fb..0eb2627e7a 100644
--- a/sql/hive-thriftserver/src/main/scala/org/apache/spark/sql/hive/thriftserver/SparkSQLDriver.scala
+++ b/sql/hive-thriftserver/src/main/scala/org/apache/spark/sql/hive/thriftserver/SparkSQLDriver.scala
@@ -25,7 +25,6 @@ import org.apache.commons.lang3.exception.ExceptionUtils
 import org.apache.hadoop.hive.metastore.api.{FieldSchema, Schema}
 import org.apache.hadoop.hive.ql.Driver
 import org.apache.hadoop.hive.ql.processors.CommandProcessorResponse
-import org.apache.log4j.LogManager
 
 import org.apache.spark.Logging
 import org.apache.spark.sql.AnalysisException
diff --git a/sql/hive-thriftserver/src/main/scala/org/apache/spark/sql/hive/thriftserver/ui/ThriftServerTab.scala b/sql/hive-thriftserver/src/main/scala/org/apache/spark/sql/hive/thriftserver/ui/ThriftServerTab.scala
index 1dc7d79436..63e6bbcfee 100644
--- a/sql/hive-thriftserver/src/main/scala/org/apache/spark/sql/hive/thriftserver/ui/ThriftServerTab.scala
+++ b/sql/hive-thriftserver/src/main/scala/org/apache/spark/sql/hive/thriftserver/ui/ThriftServerTab.scala
@@ -18,7 +18,7 @@
 package org.apache.spark.sql.hive.thriftserver.ui
 
 import org.apache.spark.{Logging, SparkContext, SparkException}
-import org.apache.spark.sql.hive.thriftserver.{HiveThriftServer2, SparkSQLEnv}
+import org.apache.spark.sql.hive.thriftserver.HiveThriftServer2
 import org.apache.spark.sql.hive.thriftserver.ui.ThriftServerTab._
 import org.apache.spark.ui.{SparkUI, SparkUITab}
 
diff --git a/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveSessionState.scala b/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveSessionState.scala
index 09f54be04d..0d4b79f531 100644
--- a/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveSessionState.scala
+++ b/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveSessionState.scala
@@ -20,7 +20,6 @@ package org.apache.spark.sql.hive
 import org.apache.spark.sql._
 import org.apache.spark.sql.catalyst.ParserInterface
 import org.apache.spark.sql.catalyst.analysis.{Analyzer, FunctionRegistry, OverrideCatalog}
-import org.apache.spark.sql.catalyst.expressions.Expression
 import org.apache.spark.sql.execution.{python, SparkPlanner}
 import org.apache.spark.sql.execution.datasources._
 import org.apache.spark.sql.internal.{SessionState, SQLConf}
diff --git a/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveStrategies.scala b/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveStrategies.scala
index 3687dd6f5a..8883e370dc 100644
--- a/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveStrategies.scala
+++ b/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveStrategies.scala
@@ -23,7 +23,8 @@ import org.apache.spark.sql.catalyst.planning._
 import org.apache.spark.sql.catalyst.plans._
 import org.apache.spark.sql.catalyst.plans.logical.LogicalPlan
 import org.apache.spark.sql.execution.{DescribeCommand => RunnableDescribeCommand, _}
-import org.apache.spark.sql.execution.datasources.{CreateTableUsing, CreateTableUsingAsSelect, DescribeCommand}
+import org.apache.spark.sql.execution.datasources.{CreateTableUsing, CreateTableUsingAsSelect,
+  DescribeCommand}
 import org.apache.spark.sql.hive.execution._
 
 private[hive] trait HiveStrategies {
diff --git a/sql/hive/src/main/scala/org/apache/spark/sql/hive/SQLBuilder.scala b/sql/hive/src/main/scala/org/apache/spark/sql/hive/SQLBuilder.scala
index bc48ed4f08..13a78c609e 100644
--- a/sql/hive/src/main/scala/org/apache/spark/sql/hive/SQLBuilder.scala
+++ b/sql/hive/src/main/scala/org/apache/spark/sql/hive/SQLBuilder.scala
@@ -24,7 +24,8 @@ import scala.util.control.NonFatal
 import org.apache.spark.Logging
 import org.apache.spark.sql.{DataFrame, SQLContext}
 import org.apache.spark.sql.catalyst.TableIdentifier
-import org.apache.spark.sql.catalyst.expressions.{Attribute, NamedExpression, NonSQLExpression, SortOrder}
+import org.apache.spark.sql.catalyst.expressions.{Attribute, NamedExpression, NonSQLExpression,
+  SortOrder}
 import org.apache.spark.sql.catalyst.optimizer.CollapseProject
 import org.apache.spark.sql.catalyst.plans.logical._
 import org.apache.spark.sql.catalyst.rules.{Rule, RuleExecutor}
diff --git a/sql/hive/src/main/scala/org/apache/spark/sql/hive/TableReader.scala b/sql/hive/src/main/scala/org/apache/spark/sql/hive/TableReader.scala
index fd465e80a8..5754bbb82d 100644
--- a/sql/hive/src/main/scala/org/apache/spark/sql/hive/TableReader.scala
+++ b/sql/hive/src/main/scala/org/apache/spark/sql/hive/TableReader.scala
@@ -23,10 +23,12 @@ import org.apache.hadoop.fs.{Path, PathFilter}
 import org.apache.hadoop.hive.conf.HiveConf
 import org.apache.hadoop.hive.metastore.api.hive_metastoreConstants._
 import org.apache.hadoop.hive.ql.exec.Utilities
-import org.apache.hadoop.hive.ql.metadata.{Hive, HiveStorageHandler, HiveUtils, Partition => HivePartition, Table => HiveTable}
+import org.apache.hadoop.hive.ql.metadata.{HiveUtils, Partition => HivePartition,
+  Table => HiveTable}
 import org.apache.hadoop.hive.ql.plan.TableDesc
 import org.apache.hadoop.hive.serde2.Deserializer
-import org.apache.hadoop.hive.serde2.objectinspector.{ObjectInspectorConverters, StructObjectInspector}
+import org.apache.hadoop.hive.serde2.objectinspector.{ObjectInspectorConverters,
+  StructObjectInspector}
 import org.apache.hadoop.hive.serde2.objectinspector.primitive._
 import org.apache.hadoop.io.Writable
 import org.apache.hadoop.mapred.{FileInputFormat, InputFormat, JobConf}
diff --git a/sql/hive/src/main/scala/org/apache/spark/sql/hive/execution/InsertIntoHiveTable.scala b/sql/hive/src/main/scala/org/apache/spark/sql/hive/execution/InsertIntoHiveTable.scala
index a89ed48608..b3d38dfdb4 100644
--- a/sql/hive/src/main/scala/org/apache/spark/sql/hive/execution/InsertIntoHiveTable.scala
+++ b/sql/hive/src/main/scala/org/apache/spark/sql/hive/execution/InsertIntoHiveTable.scala
@@ -33,7 +33,6 @@ import org.apache.spark.sql.execution.{SparkPlan, UnaryNode}
 import org.apache.spark.sql.hive._
 import org.apache.spark.sql.hive.HiveShim.{ShimFileSinkDesc => FileSinkDesc}
 import org.apache.spark.SparkException
-import org.apache.spark.sql.internal.SQLConf
 import org.apache.spark.util.SerializableJobConf
 
 private[hive]
diff --git a/sql/hive/src/main/scala/org/apache/spark/sql/hive/hiveUDFs.scala b/sql/hive/src/main/scala/org/apache/spark/sql/hive/hiveUDFs.scala
index bcafa045e0..abcc565683 100644
--- a/sql/hive/src/main/scala/org/apache/spark/sql/hive/hiveUDFs.scala
+++ b/sql/hive/src/main/scala/org/apache/spark/sql/hive/hiveUDFs.scala
@@ -26,7 +26,8 @@ import org.apache.hadoop.hive.ql.udf.{UDFType => HiveUDFType}
 import org.apache.hadoop.hive.ql.udf.generic._
 import org.apache.hadoop.hive.ql.udf.generic.GenericUDF._
 import org.apache.hadoop.hive.ql.udf.generic.GenericUDFUtils.ConversionHelper
-import org.apache.hadoop.hive.serde2.objectinspector.{ConstantObjectInspector, ObjectInspector, ObjectInspectorFactory}
+import org.apache.hadoop.hive.serde2.objectinspector.{ConstantObjectInspector, ObjectInspector,
+  ObjectInspectorFactory}
 import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspectorFactory.ObjectInspectorOptions
 
 import org.apache.spark.Logging
diff --git a/sql/hive/src/test/scala/org/apache/spark/sql/hive/CachedTableSuite.scala b/sql/hive/src/test/scala/org/apache/spark/sql/hive/CachedTableSuite.scala
index 86f02e68e5..656c1317c1 100644
--- a/sql/hive/src/test/scala/org/apache/spark/sql/hive/CachedTableSuite.scala
+++ b/sql/hive/src/test/scala/org/apache/spark/sql/hive/CachedTableSuite.scala
@@ -21,7 +21,6 @@ import java.io.File
 
 import org.apache.spark.sql.{AnalysisException, QueryTest, SaveMode}
 import org.apache.spark.sql.execution.columnar.InMemoryColumnarTableScan
-import org.apache.spark.sql.execution.datasources.parquet.ParquetRelation
 import org.apache.spark.sql.hive.test.TestHiveSingleton
 import org.apache.spark.storage.RDDBlockId
 import org.apache.spark.util.Utils
diff --git a/sql/hive/src/test/scala/org/apache/spark/sql/hive/execution/HiveOperatorQueryableSuite.scala b/sql/hive/src/test/scala/org/apache/spark/sql/hive/execution/HiveOperatorQueryableSuite.scala
index 9bdc24162b..b252c6ee2f 100644
--- a/sql/hive/src/test/scala/org/apache/spark/sql/hive/execution/HiveOperatorQueryableSuite.scala
+++ b/sql/hive/src/test/scala/org/apache/spark/sql/hive/execution/HiveOperatorQueryableSuite.scala
@@ -18,7 +18,7 @@
 package org.apache.spark.sql.hive.execution
 
 import org.apache.spark.sql.{QueryTest, Row}
-import org.apache.spark.sql.hive.test.{TestHive, TestHiveSingleton}
+import org.apache.spark.sql.hive.test.TestHiveSingleton
 
 /**
  * A set of tests that validates commands can also be queried by like a table
diff --git a/streaming/src/main/scala/org/apache/spark/streaming/api/java/JavaStreamingContext.scala b/streaming/src/main/scala/org/apache/spark/streaming/api/java/JavaStreamingContext.scala
index f8f1336693..860b802725 100644
--- a/streaming/src/main/scala/org/apache/spark/streaming/api/java/JavaStreamingContext.scala
+++ b/streaming/src/main/scala/org/apache/spark/streaming/api/java/JavaStreamingContext.scala
@@ -29,7 +29,6 @@ import org.apache.hadoop.fs.Path
 import org.apache.hadoop.mapreduce.{InputFormat => NewInputFormat}
 
 import org.apache.spark.{SparkConf, SparkContext}
-import org.apache.spark.annotation.Experimental
 import org.apache.spark.api.java.{JavaPairRDD, JavaRDD, JavaSparkContext}
 import org.apache.spark.api.java.function.{Function => JFunction, Function2 => JFunction2}
 import org.apache.spark.api.java.function.{Function0 => JFunction0}
diff --git a/streaming/src/main/scala/org/apache/spark/streaming/api/java/JavaStreamingListener.scala b/streaming/src/main/scala/org/apache/spark/streaming/api/java/JavaStreamingListener.scala
index 7bfd6bd5af..db0bae9958 100644
--- a/streaming/src/main/scala/org/apache/spark/streaming/api/java/JavaStreamingListener.scala
+++ b/streaming/src/main/scala/org/apache/spark/streaming/api/java/JavaStreamingListener.scala
@@ -18,7 +18,6 @@
 package org.apache.spark.streaming.api.java
 
 import org.apache.spark.streaming.Time
-import org.apache.spark.streaming.scheduler.StreamingListener
 
 private[streaming] trait PythonStreamingListener{
 
diff --git a/streaming/src/main/scala/org/apache/spark/streaming/api/python/PythonDStream.scala b/streaming/src/main/scala/org/apache/spark/streaming/api/python/PythonDStream.scala
index 8c9beccc29..aeff4d7a98 100644
--- a/streaming/src/main/scala/org/apache/spark/streaming/api/python/PythonDStream.scala
+++ b/streaming/src/main/scala/org/apache/spark/streaming/api/python/PythonDStream.scala
@@ -24,8 +24,6 @@ import java.util.{ArrayList => JArrayList, List => JList}
 import scala.collection.JavaConverters._
 import scala.language.existentials
 
-import py4j.GatewayServer
-
 import org.apache.spark.SparkException
 import org.apache.spark.api.java._
 import org.apache.spark.rdd.RDD
diff --git a/streaming/src/main/scala/org/apache/spark/streaming/dstream/FlatMapValuedDStream.scala b/streaming/src/main/scala/org/apache/spark/streaming/dstream/FlatMapValuedDStream.scala
index 778d556d2e..f5b1e5f3a1 100644
--- a/streaming/src/main/scala/org/apache/spark/streaming/dstream/FlatMapValuedDStream.scala
+++ b/streaming/src/main/scala/org/apache/spark/streaming/dstream/FlatMapValuedDStream.scala
@@ -19,7 +19,6 @@ package org.apache.spark.streaming.dstream
 
 import scala.reflect.ClassTag
 
-import org.apache.spark.SparkContext._
 import org.apache.spark.rdd.RDD
 import org.apache.spark.streaming.{Duration, Time}
 
diff --git a/streaming/src/main/scala/org/apache/spark/streaming/dstream/InputDStream.scala b/streaming/src/main/scala/org/apache/spark/streaming/dstream/InputDStream.scala
index 76f6230f36..0b6b191dbe 100644
--- a/streaming/src/main/scala/org/apache/spark/streaming/dstream/InputDStream.scala
+++ b/streaming/src/main/scala/org/apache/spark/streaming/dstream/InputDStream.scala
@@ -23,7 +23,6 @@ import org.apache.spark.SparkContext
 import org.apache.spark.rdd.RDDOperationScope
 import org.apache.spark.streaming.{Duration, StreamingContext, Time}
 import org.apache.spark.streaming.scheduler.RateController
-import org.apache.spark.streaming.scheduler.rate.RateEstimator
 import org.apache.spark.util.Utils
 
 /**
diff --git a/streaming/src/main/scala/org/apache/spark/streaming/dstream/MapValuedDStream.scala b/streaming/src/main/scala/org/apache/spark/streaming/dstream/MapValuedDStream.scala
index 855c3dd096..c209f86c86 100644
--- a/streaming/src/main/scala/org/apache/spark/streaming/dstream/MapValuedDStream.scala
+++ b/streaming/src/main/scala/org/apache/spark/streaming/dstream/MapValuedDStream.scala
@@ -19,7 +19,6 @@ package org.apache.spark.streaming.dstream
 
 import scala.reflect.ClassTag
 
-import org.apache.spark.SparkContext._
 import org.apache.spark.rdd.RDD
 import org.apache.spark.streaming.{Duration, Time}
 
diff --git a/streaming/src/main/scala/org/apache/spark/streaming/dstream/RawInputDStream.scala b/streaming/src/main/scala/org/apache/spark/streaming/dstream/RawInputDStream.scala
index 409c565380..c6afac934c 100644
--- a/streaming/src/main/scala/org/apache/spark/streaming/dstream/RawInputDStream.scala
+++ b/streaming/src/main/scala/org/apache/spark/streaming/dstream/RawInputDStream.scala
@@ -25,8 +25,8 @@ import java.util.concurrent.ArrayBlockingQueue
 
 import scala.reflect.ClassTag
 
-import org.apache.spark.{Logging, SparkEnv}
-import org.apache.spark.storage.{StorageLevel, StreamBlockId}
+import org.apache.spark.Logging
+import org.apache.spark.storage.StorageLevel
 import org.apache.spark.streaming.StreamingContext
 import org.apache.spark.streaming.receiver.Receiver
 
diff --git a/streaming/src/main/scala/org/apache/spark/streaming/dstream/ReducedWindowedDStream.scala b/streaming/src/main/scala/org/apache/spark/streaming/dstream/ReducedWindowedDStream.scala
index 817ecc1ace..a9be2f213f 100644
--- a/streaming/src/main/scala/org/apache/spark/streaming/dstream/ReducedWindowedDStream.scala
+++ b/streaming/src/main/scala/org/apache/spark/streaming/dstream/ReducedWindowedDStream.scala
@@ -21,8 +21,7 @@ import scala.collection.mutable.ArrayBuffer
 import scala.reflect.ClassTag
 
 import org.apache.spark.Partitioner
-import org.apache.spark.SparkContext._
-import org.apache.spark.rdd.{CoGroupedRDD, MapPartitionsRDD, RDD}
+import org.apache.spark.rdd.{CoGroupedRDD, RDD}
 import org.apache.spark.storage.StorageLevel
 import org.apache.spark.streaming.{Duration, Interval, Time}
 
diff --git a/streaming/src/main/scala/org/apache/spark/streaming/dstream/ShuffledDStream.scala b/streaming/src/main/scala/org/apache/spark/streaming/dstream/ShuffledDStream.scala
index 0fe15440dd..6971a66b38 100644
--- a/streaming/src/main/scala/org/apache/spark/streaming/dstream/ShuffledDStream.scala
+++ b/streaming/src/main/scala/org/apache/spark/streaming/dstream/ShuffledDStream.scala
@@ -20,7 +20,6 @@ package org.apache.spark.streaming.dstream
 import scala.reflect.ClassTag
 
 import org.apache.spark.Partitioner
-import org.apache.spark.SparkContext._
 import org.apache.spark.rdd.RDD
 import org.apache.spark.streaming.{Duration, Time}
 
diff --git a/streaming/src/main/scala/org/apache/spark/streaming/dstream/StateDStream.scala b/streaming/src/main/scala/org/apache/spark/streaming/dstream/StateDStream.scala
index fedffb2395..68eff89030 100644
--- a/streaming/src/main/scala/org/apache/spark/streaming/dstream/StateDStream.scala
+++ b/streaming/src/main/scala/org/apache/spark/streaming/dstream/StateDStream.scala
@@ -20,7 +20,6 @@ package org.apache.spark.streaming.dstream
 import scala.reflect.ClassTag
 
 import org.apache.spark.Partitioner
-import org.apache.spark.SparkContext._
 import org.apache.spark.rdd.RDD
 import org.apache.spark.storage.StorageLevel
 import org.apache.spark.streaming.{Duration, Time}
diff --git a/streaming/src/main/scala/org/apache/spark/streaming/rdd/MapWithStateRDD.scala b/streaming/src/main/scala/org/apache/spark/streaming/rdd/MapWithStateRDD.scala
index 6ab1956bed..8119d808ff 100644
--- a/streaming/src/main/scala/org/apache/spark/streaming/rdd/MapWithStateRDD.scala
+++ b/streaming/src/main/scala/org/apache/spark/streaming/rdd/MapWithStateRDD.scala
@@ -17,13 +17,13 @@
 
 package org.apache.spark.streaming.rdd
 
-import java.io.{IOException, ObjectInputStream, ObjectOutputStream}
+import java.io.{IOException, ObjectOutputStream}
 
 import scala.collection.mutable.ArrayBuffer
 import scala.reflect.ClassTag
 
 import org.apache.spark._
-import org.apache.spark.rdd.{MapPartitionsRDD, RDD}
+import org.apache.spark.rdd.RDD
 import org.apache.spark.streaming.{State, StateImpl, Time}
 import org.apache.spark.streaming.util.{EmptyStateMap, StateMap}
 import org.apache.spark.util.Utils
diff --git a/streaming/src/main/scala/org/apache/spark/streaming/scheduler/JobSet.scala b/streaming/src/main/scala/org/apache/spark/streaming/scheduler/JobSet.scala
index 6e7232a2a0..66d5ffb797 100644
--- a/streaming/src/main/scala/org/apache/spark/streaming/scheduler/JobSet.scala
+++ b/streaming/src/main/scala/org/apache/spark/streaming/scheduler/JobSet.scala
@@ -18,10 +18,8 @@
 package org.apache.spark.streaming.scheduler
 
 import scala.collection.mutable.HashSet
-import scala.util.Failure
 
 import org.apache.spark.streaming.Time
-import org.apache.spark.util.Utils
 
 /** Class representing a set of Jobs
   * belong to the same batch.
diff --git a/streaming/src/main/scala/org/apache/spark/streaming/scheduler/ReceivedBlockTracker.scala b/streaming/src/main/scala/org/apache/spark/streaming/scheduler/ReceivedBlockTracker.scala
index 5f1c671c3c..5ed5ae6358 100644
--- a/streaming/src/main/scala/org/apache/spark/streaming/scheduler/ReceivedBlockTracker.scala
+++ b/streaming/src/main/scala/org/apache/spark/streaming/scheduler/ReceivedBlockTracker.scala
@@ -30,7 +30,7 @@ import org.apache.hadoop.fs.Path
 import org.apache.spark.{Logging, SparkConf}
 import org.apache.spark.network.util.JavaUtils
 import org.apache.spark.streaming.Time
-import org.apache.spark.streaming.util.{BatchedWriteAheadLog, WriteAheadLog, WriteAheadLogUtils}
+import org.apache.spark.streaming.util.{WriteAheadLog, WriteAheadLogUtils}
 import org.apache.spark.util.{Clock, Utils}
 
 /** Trait representing any event in the ReceivedBlockTracker that updates its state. */
diff --git a/streaming/src/main/scala/org/apache/spark/streaming/scheduler/ReceiverInfo.scala b/streaming/src/main/scala/org/apache/spark/streaming/scheduler/ReceiverInfo.scala
index 3b35964114..d16e158da3 100644
--- a/streaming/src/main/scala/org/apache/spark/streaming/scheduler/ReceiverInfo.scala
+++ b/streaming/src/main/scala/org/apache/spark/streaming/scheduler/ReceiverInfo.scala
@@ -18,7 +18,6 @@
 package org.apache.spark.streaming.scheduler
 
 import org.apache.spark.annotation.DeveloperApi
-import org.apache.spark.rpc.RpcEndpointRef
 
 /**
  * :: DeveloperApi ::
diff --git a/streaming/src/main/scala/org/apache/spark/streaming/ui/BatchPage.scala b/streaming/src/main/scala/org/apache/spark/streaming/ui/BatchPage.scala
index c8a2c17bbd..1ef26d2f86 100644
--- a/streaming/src/main/scala/org/apache/spark/streaming/ui/BatchPage.scala
+++ b/streaming/src/main/scala/org/apache/spark/streaming/ui/BatchPage.scala
@@ -24,7 +24,7 @@ import scala.xml._
 import org.apache.commons.lang3.StringEscapeUtils
 
 import org.apache.spark.streaming.Time
-import org.apache.spark.streaming.ui.StreamingJobProgressListener.{OutputOpId, SparkJobId}
+import org.apache.spark.streaming.ui.StreamingJobProgressListener.SparkJobId
 import org.apache.spark.ui.{UIUtils => SparkUIUtils, WebUIPage}
 import org.apache.spark.ui.jobs.UIData.JobUIData
 
diff --git a/streaming/src/main/scala/org/apache/spark/streaming/ui/StreamingPage.scala b/streaming/src/main/scala/org/apache/spark/streaming/ui/StreamingPage.scala
index 2a5d0839fd..eb1e5b0fdc 100644
--- a/streaming/src/main/scala/org/apache/spark/streaming/ui/StreamingPage.scala
+++ b/streaming/src/main/scala/org/apache/spark/streaming/ui/StreamingPage.scala
@@ -17,8 +17,6 @@
 
 package org.apache.spark.streaming.ui
 
-import java.text.SimpleDateFormat
-import java.util.Date
 import java.util.concurrent.TimeUnit
 import javax.servlet.http.HttpServletRequest
 
diff --git a/streaming/src/test/scala/org/apache/spark/streaming/StreamingListenerSuite.scala b/streaming/src/test/scala/org/apache/spark/streaming/StreamingListenerSuite.scala
index 19c89fcf67..9f96ee9b95 100644
--- a/streaming/src/test/scala/org/apache/spark/streaming/StreamingListenerSuite.scala
+++ b/streaming/src/test/scala/org/apache/spark/streaming/StreamingListenerSuite.scala
@@ -20,7 +20,7 @@ package org.apache.spark.streaming
 import java.util.concurrent.ConcurrentLinkedQueue
 
 import scala.collection.JavaConverters._
-import scala.collection.mutable.{HashMap, SynchronizedMap}
+import scala.collection.mutable.HashMap
 import scala.concurrent.ExecutionContext.Implicits.global
 import scala.concurrent.Future
 
diff --git a/streaming/src/test/scala/org/apache/spark/streaming/scheduler/RateControllerSuite.scala b/streaming/src/test/scala/org/apache/spark/streaming/scheduler/RateControllerSuite.scala
index 1eb52b7029..37ca0ce2f6 100644
--- a/streaming/src/test/scala/org/apache/spark/streaming/scheduler/RateControllerSuite.scala
+++ b/streaming/src/test/scala/org/apache/spark/streaming/scheduler/RateControllerSuite.scala
@@ -17,8 +17,6 @@
 
 package org.apache.spark.streaming.scheduler
 
-import scala.collection.mutable
-
 import org.scalatest.concurrent.Eventually._
 import org.scalatest.time.SpanSugar._
 
diff --git a/yarn/src/main/scala/org/apache/spark/deploy/yarn/ApplicationMasterArguments.scala b/yarn/src/main/scala/org/apache/spark/deploy/yarn/ApplicationMasterArguments.scala
index 87f50875e3..6987e5a55f 100644
--- a/yarn/src/main/scala/org/apache/spark/deploy/yarn/ApplicationMasterArguments.scala
+++ b/yarn/src/main/scala/org/apache/spark/deploy/yarn/ApplicationMasterArguments.scala
@@ -19,7 +19,6 @@ package org.apache.spark.deploy.yarn
 
 import scala.collection.mutable.ArrayBuffer
 
-import org.apache.spark.deploy.yarn.YarnSparkHadoopUtil._
 import org.apache.spark.util.{IntParam, MemoryParam}
 
 class ApplicationMasterArguments(val args: Array[String]) {
diff --git a/yarn/src/main/scala/org/apache/spark/deploy/yarn/Client.scala b/yarn/src/main/scala/org/apache/spark/deploy/yarn/Client.scala
index dac3ea2517..be45e9597f 100644
--- a/yarn/src/main/scala/org/apache/spark/deploy/yarn/Client.scala
+++ b/yarn/src/main/scala/org/apache/spark/deploy/yarn/Client.scala
@@ -19,15 +19,13 @@ package org.apache.spark.deploy.yarn
 
 import java.io.{ByteArrayInputStream, DataInputStream, File, FileOutputStream, IOException,
   OutputStreamWriter}
-import java.net.{InetAddress, UnknownHostException, URI, URISyntaxException}
+import java.net.{InetAddress, UnknownHostException, URI}
 import java.nio.ByteBuffer
-import java.security.PrivilegedExceptionAction
 import java.util.{Properties, UUID}
 import java.util.zip.{ZipEntry, ZipOutputStream}
 
 import scala.collection.JavaConverters._
 import scala.collection.mutable.{ArrayBuffer, HashMap, HashSet, ListBuffer, Map}
-import scala.reflect.runtime.universe
 import scala.util.{Failure, Success, Try}
 import scala.util.control.NonFatal
 
@@ -38,10 +36,9 @@ import org.apache.hadoop.conf.Configuration
 import org.apache.hadoop.fs._
 import org.apache.hadoop.fs.permission.FsPermission
 import org.apache.hadoop.hdfs.security.token.delegation.DelegationTokenIdentifier
-import org.apache.hadoop.io.{DataOutputBuffer, Text}
+import org.apache.hadoop.io.DataOutputBuffer
 import org.apache.hadoop.mapreduce.MRJobConfig
 import org.apache.hadoop.security.{Credentials, UserGroupInformation}
-import org.apache.hadoop.security.token.{Token, TokenIdentifier}
 import org.apache.hadoop.util.StringUtils
 import org.apache.hadoop.yarn.api._
 import org.apache.hadoop.yarn.api.ApplicationConstants.Environment
diff --git a/yarn/src/main/scala/org/apache/spark/deploy/yarn/YarnRMClient.scala b/yarn/src/main/scala/org/apache/spark/deploy/yarn/YarnRMClient.scala
index af83cf6a77..98505b93dd 100644
--- a/yarn/src/main/scala/org/apache/spark/deploy/yarn/YarnRMClient.scala
+++ b/yarn/src/main/scala/org/apache/spark/deploy/yarn/YarnRMClient.scala
@@ -19,8 +19,8 @@ package org.apache.spark.deploy.yarn
 
 import java.util.{List => JList}
 
-import scala.collection.{Map, Set}
 import scala.collection.JavaConverters._
+import scala.collection.Map
 import scala.util.Try
 
 import org.apache.hadoop.conf.Configuration
@@ -32,7 +32,6 @@ import org.apache.hadoop.yarn.webapp.util.WebAppUtils
 
 import org.apache.spark.{Logging, SecurityManager, SparkConf}
 import org.apache.spark.rpc.RpcEndpointRef
-import org.apache.spark.scheduler.SplitInfo
 import org.apache.spark.util.Utils
 
 /**
diff --git a/yarn/src/test/scala/org/apache/spark/deploy/yarn/ClientDistributedCacheManagerSuite.scala b/yarn/src/test/scala/org/apache/spark/deploy/yarn/ClientDistributedCacheManagerSuite.scala
index 4cffbb2e9b..ac8f663df2 100644
--- a/yarn/src/test/scala/org/apache/spark/deploy/yarn/ClientDistributedCacheManagerSuite.scala
+++ b/yarn/src/test/scala/org/apache/spark/deploy/yarn/ClientDistributedCacheManagerSuite.scala
@@ -26,11 +26,10 @@ import org.apache.hadoop.conf.Configuration
 import org.apache.hadoop.fs.FileStatus
 import org.apache.hadoop.fs.FileSystem
 import org.apache.hadoop.fs.Path
-import org.apache.hadoop.fs.permission.FsAction
 import org.apache.hadoop.yarn.api.records.LocalResource
 import org.apache.hadoop.yarn.api.records.LocalResourceType
 import org.apache.hadoop.yarn.api.records.LocalResourceVisibility
-import org.apache.hadoop.yarn.util.{ConverterUtils, Records}
+import org.apache.hadoop.yarn.util.ConverterUtils
 import org.mockito.Mockito.when
 import org.scalatest.mock.MockitoSugar
 
diff --git a/yarn/src/test/scala/org/apache/spark/deploy/yarn/YarnClusterSuite.scala b/yarn/src/test/scala/org/apache/spark/deploy/yarn/YarnClusterSuite.scala
index 60d35d3452..e935163c34 100644
--- a/yarn/src/test/scala/org/apache/spark/deploy/yarn/YarnClusterSuite.scala
+++ b/yarn/src/test/scala/org/apache/spark/deploy/yarn/YarnClusterSuite.scala
@@ -19,7 +19,7 @@ package org.apache.spark.deploy.yarn
 
 import java.io.File
 import java.net.URL
-import java.util.{HashMap => JHashMap, Properties}
+import java.util.{HashMap => JHashMap}
 
 import scala.collection.mutable
 import scala.concurrent.duration._
diff --git a/yarn/src/test/scala/org/apache/spark/network/shuffle/ShuffleTestAccessor.scala b/yarn/src/test/scala/org/apache/spark/network/shuffle/ShuffleTestAccessor.scala
index d6902c7bb0..1fed2562fc 100644
--- a/yarn/src/test/scala/org/apache/spark/network/shuffle/ShuffleTestAccessor.scala
+++ b/yarn/src/test/scala/org/apache/spark/network/shuffle/ShuffleTestAccessor.scala
@@ -16,7 +16,7 @@
  */
 package org.apache.spark.network.shuffle
 
-import java.io.{File, IOException}
+import java.io.File
 import java.util.concurrent.ConcurrentMap
 
 import org.apache.hadoop.yarn.api.records.ApplicationId