[SPARK-19227][SPARK-19251] remove unused imports and outdated comments

## What changes were proposed in this pull request?
remove ununsed imports and outdated comments, and fix some minor code style issue.

## How was this patch tested?
existing ut

Author: uncleGen <hustyugm@gmail.com>

Closes #16591 from uncleGen/SPARK-19227.

6 files changed, 5 insertions, 7 deletions

diff --git a/external/kafka-0-10-sql/src/main/scala/org/apache/spark/sql/kafka010/KafkaSource.scala b/external/kafka-0-10-sql/src/main/scala/org/apache/spark/sql/kafka010/KafkaSource.scala
index 43b8d9d6d7..8e6c93e672 100644
--- a/external/kafka-0-10-sql/src/main/scala/org/apache/spark/sql/kafka010/KafkaSource.scala
+++ b/external/kafka-0-10-sql/src/main/scala/org/apache/spark/sql/kafka010/KafkaSource.scala
@@ -24,7 +24,7 @@ import java.nio.charset.StandardCharsets
 import scala.collection.JavaConverters._
 import scala.util.control.NonFatal
 
-import org.apache.kafka.clients.consumer.{Consumer, ConsumerConfig, KafkaConsumer, OffsetOutOfRangeException}
+import org.apache.kafka.clients.consumer.{Consumer, ConsumerConfig, KafkaConsumer}
 import org.apache.kafka.clients.consumer.internals.NoOpConsumerRebalanceListener
 import org.apache.kafka.common.TopicPartition
 
diff --git a/external/kafka-0-10/src/main/scala/org/apache/spark/streaming/kafka010/KafkaRDD.scala b/external/kafka-0-10/src/main/scala/org/apache/spark/streaming/kafka010/KafkaRDD.scala
index 8f38095208..bf8adbe42f 100644
--- a/external/kafka-0-10/src/main/scala/org/apache/spark/streaming/kafka010/KafkaRDD.scala
+++ b/external/kafka-0-10/src/main/scala/org/apache/spark/streaming/kafka010/KafkaRDD.scala
@@ -24,7 +24,7 @@ import scala.collection.mutable.ArrayBuffer
 import org.apache.kafka.clients.consumer.{ ConsumerConfig, ConsumerRecord }
 import org.apache.kafka.common.TopicPartition
 
-import org.apache.spark.{Partition, SparkContext, SparkException, TaskContext}
+import org.apache.spark.{Partition, SparkContext, TaskContext}
 import org.apache.spark.internal.Logging
 import org.apache.spark.partial.{BoundedDouble, PartialResult}
 import org.apache.spark.rdd.RDD
diff --git a/external/kafka-0-10/src/main/scala/org/apache/spark/streaming/kafka010/KafkaUtils.scala b/external/kafka-0-10/src/main/scala/org/apache/spark/streaming/kafka010/KafkaUtils.scala
index 37046329e5..e6bdef0451 100644
--- a/external/kafka-0-10/src/main/scala/org/apache/spark/streaming/kafka010/KafkaUtils.scala
+++ b/external/kafka-0-10/src/main/scala/org/apache/spark/streaming/kafka010/KafkaUtils.scala
@@ -25,7 +25,6 @@ import org.apache.kafka.common.TopicPartition
 import org.apache.spark.SparkContext
 import org.apache.spark.annotation.Experimental
 import org.apache.spark.api.java.{ JavaRDD, JavaSparkContext }
-import org.apache.spark.api.java.function.{ Function0 => JFunction0 }
 import org.apache.spark.internal.Logging
 import org.apache.spark.rdd.RDD
 import org.apache.spark.streaming.StreamingContext
diff --git a/external/kinesis-asl/src/main/scala/org/apache/spark/examples/streaming/KinesisWordCountASL.scala b/external/kinesis-asl/src/main/scala/org/apache/spark/examples/streaming/KinesisWordCountASL.scala
index 859fe9edb4..a70c13d7d6 100644
--- a/external/kinesis-asl/src/main/scala/org/apache/spark/examples/streaming/KinesisWordCountASL.scala
+++ b/external/kinesis-asl/src/main/scala/org/apache/spark/examples/streaming/KinesisWordCountASL.scala
@@ -22,7 +22,7 @@ import java.nio.ByteBuffer
 
 import scala.util.Random
 
-import com.amazonaws.auth.{BasicAWSCredentials, DefaultAWSCredentialsProviderChain}
+import com.amazonaws.auth.DefaultAWSCredentialsProviderChain
 import com.amazonaws.regions.RegionUtils
 import com.amazonaws.services.kinesis.AmazonKinesisClient
 import com.amazonaws.services.kinesis.clientlibrary.lib.worker.InitialPositionInStream
diff --git a/external/kinesis-asl/src/main/scala/org/apache/spark/streaming/kinesis/KinesisCheckpointer.scala b/external/kinesis-asl/src/main/scala/org/apache/spark/streaming/kinesis/KinesisCheckpointer.scala
index 70b5cc7ca0..3e697f36a4 100644
--- a/external/kinesis-asl/src/main/scala/org/apache/spark/streaming/kinesis/KinesisCheckpointer.scala
+++ b/external/kinesis-asl/src/main/scala/org/apache/spark/streaming/kinesis/KinesisCheckpointer.scala
@@ -26,7 +26,7 @@ import com.amazonaws.services.kinesis.clientlibrary.types.ShutdownReason
 import org.apache.spark.internal.Logging
 import org.apache.spark.streaming.Duration
 import org.apache.spark.streaming.util.RecurringTimer
-import org.apache.spark.util.{Clock, SystemClock, ThreadUtils}
+import org.apache.spark.util.{Clock, SystemClock}
 
 /**
  * This is a helper class for managing Kinesis checkpointing.
diff --git a/external/kinesis-asl/src/test/scala/org/apache/spark/streaming/kinesis/KinesisCheckpointerSuite.scala b/external/kinesis-asl/src/test/scala/org/apache/spark/streaming/kinesis/KinesisCheckpointerSuite.scala
index e1499a8220..bcaed628a8 100644
--- a/external/kinesis-asl/src/test/scala/org/apache/spark/streaming/kinesis/KinesisCheckpointerSuite.scala
+++ b/external/kinesis-asl/src/test/scala/org/apache/spark/streaming/kinesis/KinesisCheckpointerSuite.scala
@@ -17,7 +17,7 @@
 
 package org.apache.spark.streaming.kinesis
 
-import java.util.concurrent.{ExecutorService, TimeoutException}
+import java.util.concurrent.TimeoutException
 
 import scala.concurrent.{Await, ExecutionContext, Future}
 import scala.concurrent.duration._
@@ -30,7 +30,6 @@ import org.mockito.invocation.InvocationOnMock
 import org.mockito.stubbing.Answer
 import org.scalatest.{BeforeAndAfterEach, PrivateMethodTester}
 import org.scalatest.concurrent.Eventually
-import org.scalatest.concurrent.Eventually._
 import org.scalatest.mock.MockitoSugar
 
 import org.apache.spark.streaming.{Duration, TestSuiteBase}