[SPARK-15645][STREAMING] Fix some typos of Streaming module

## What changes were proposed in this pull request?

No code change, just some typo fixing.

## How was this patch tested?

Manually run project build with testing, and build is successful.

Author: Xin Ren <iamshrek@126.com>

Closes #13385 from keypointt/codeWalkThroughStreaming.

5 files changed, 9 insertions, 10 deletions

diff --git a/streaming/src/main/scala/org/apache/spark/streaming/dstream/DStream.scala b/streaming/src/main/scala/org/apache/spark/streaming/dstream/DStream.scala
index 01dcfcf24b..147e8c1290 100644
--- a/streaming/src/main/scala/org/apache/spark/streaming/dstream/DStream.scala
+++ b/streaming/src/main/scala/org/apache/spark/streaming/dstream/DStream.scala
@@ -52,7 +52,7 @@ import org.apache.spark.util.{CallSite, Utils}
  * `join`. These operations are automatically available on any DStream of pairs
  * (e.g., DStream[(Int, Int)] through implicit conversions.
  *
- * DStreams internally is characterized by a few basic properties:
+ * A DStream internally is characterized by a few basic properties:
  *  - A list of other DStreams that the DStream depends on
  *  - A time interval at which the DStream generates an RDD
  *  - A function that is used to generate an RDD after each time interval
diff --git a/streaming/src/main/scala/org/apache/spark/streaming/receiver/BlockGenerator.scala b/streaming/src/main/scala/org/apache/spark/streaming/receiver/BlockGenerator.scala
index 4592e015ed..90309c0145 100644
--- a/streaming/src/main/scala/org/apache/spark/streaming/receiver/BlockGenerator.scala
+++ b/streaming/src/main/scala/org/apache/spark/streaming/receiver/BlockGenerator.scala
@@ -86,13 +86,13 @@ private[streaming] class BlockGenerator(
   /**
    * The BlockGenerator can be in 5 possible states, in the order as follows.
    *
-   *  - Initialized: Nothing has been started
+   *  - Initialized: Nothing has been started.
    *  - Active: start() has been called, and it is generating blocks on added data.
    *  - StoppedAddingData: stop() has been called, the adding of data has been stopped,
    *                       but blocks are still being generated and pushed.
    *  - StoppedGeneratingBlocks: Generating of blocks has been stopped, but
    *                             they are still being pushed.
-   *  - StoppedAll: Everything has stopped, and the BlockGenerator object can be GCed.
+   *  - StoppedAll: Everything has been stopped, and the BlockGenerator object can be GCed.
    */
   private object GeneratorState extends Enumeration {
     type GeneratorState = Value
@@ -148,7 +148,7 @@ private[streaming] class BlockGenerator(
     blockIntervalTimer.stop(interruptTimer = false)
     synchronized { state = StoppedGeneratingBlocks }
 
-    // Wait for the queue to drain and mark generated as stopped
+    // Wait for the queue to drain and mark state as StoppedAll
     logInfo("Waiting for block pushing thread to terminate")
     blockPushingThread.join()
     synchronized { state = StoppedAll }
diff --git a/streaming/src/main/scala/org/apache/spark/streaming/receiver/Receiver.scala b/streaming/src/main/scala/org/apache/spark/streaming/receiver/Receiver.scala
index 5157ca62dc..d91a64df32 100644
--- a/streaming/src/main/scala/org/apache/spark/streaming/receiver/Receiver.scala
+++ b/streaming/src/main/scala/org/apache/spark/streaming/receiver/Receiver.scala
@@ -32,7 +32,7 @@ import org.apache.spark.storage.StorageLevel
  * should define the setup steps necessary to start receiving data,
  * and `onStop()` should define the cleanup steps necessary to stop receiving data.
  * Exceptions while receiving can be handled either by restarting the receiver with `restart(...)`
- * or stopped completely by `stop(...)` or
+ * or stopped completely by `stop(...)`.
  *
  * A custom receiver in Scala would look like this.
  *
@@ -45,7 +45,7 @@ import org.apache.spark.storage.StorageLevel
  *          // Call store(...) in those threads to store received data into Spark's memory.
  *
  *          // Call stop(...), restart(...) or reportError(...) on any thread based on how
- *          // different errors needs to be handled.
+ *          // different errors need to be handled.
  *
  *          // See corresponding method documentation for more details
  *      }
@@ -71,7 +71,7 @@ import org.apache.spark.storage.StorageLevel
  *          // Call store(...) in those threads to store received data into Spark's memory.
  *
  *          // Call stop(...), restart(...) or reportError(...) on any thread based on how
- *          // different errors needs to be handled.
+ *          // different errors need to be handled.
  *
  *          // See corresponding method documentation for more details
  *     }
diff --git a/streaming/src/main/scala/org/apache/spark/streaming/scheduler/JobGenerator.scala b/streaming/src/main/scala/org/apache/spark/streaming/scheduler/JobGenerator.scala
index 8f9421fc09..19c88f1ee0 100644
--- a/streaming/src/main/scala/org/apache/spark/streaming/scheduler/JobGenerator.scala
+++ b/streaming/src/main/scala/org/apache/spark/streaming/scheduler/JobGenerator.scala
@@ -19,7 +19,6 @@ package org.apache.spark.streaming.scheduler
 
 import scala.util.{Failure, Success, Try}
 
-import org.apache.spark.SparkEnv
 import org.apache.spark.internal.Logging
 import org.apache.spark.rdd.RDD
 import org.apache.spark.streaming.{Checkpoint, CheckpointWriter, Time}
@@ -239,7 +238,7 @@ class JobGenerator(jobScheduler: JobScheduler) extends Logging {
     logInfo("Restarted JobGenerator at " + restartTime)
   }
 
-  /** Generate jobs and perform checkpoint for the given `time`.  */
+  /** Generate jobs and perform checkpointing for the given `time`.  */
   private def generateJobs(time: Time) {
     // Checkpoint all RDDs marked for checkpointing to ensure their lineages are
     // truncated periodically. Otherwise, we may run into stack overflows (SPARK-6847).
diff --git a/streaming/src/main/scala/org/apache/spark/streaming/scheduler/ReceiverTracker.scala b/streaming/src/main/scala/org/apache/spark/streaming/scheduler/ReceiverTracker.scala
index 9aa2f0bbb9..b9d898a723 100644
--- a/streaming/src/main/scala/org/apache/spark/streaming/scheduler/ReceiverTracker.scala
+++ b/streaming/src/main/scala/org/apache/spark/streaming/scheduler/ReceiverTracker.scala
@@ -20,7 +20,7 @@ package org.apache.spark.streaming.scheduler
 import java.util.concurrent.{CountDownLatch, TimeUnit}
 
 import scala.collection.mutable.HashMap
-import scala.concurrent.{ExecutionContext, Future}
+import scala.concurrent.ExecutionContext
 import scala.language.existentials
 import scala.util.{Failure, Success}