[MINOR][SQL] Remove extra anonymous closure within functional transformations

## What changes were proposed in this pull request?

This PR removes extra anonymous closure within functional transformations.

For example,

```scala
.map(item => {
  ...
})
```

which can be just simply as below:

```scala
.map { item =>
  ...
}
```

## How was this patch tested?

Related unit tests and `sbt scalastyle`.

Author: hyukjinkwon <gurwls223@gmail.com>

Closes #12382 from HyukjinKwon/minor-extra-closers.

3 files changed, 8 insertions, 8 deletions

diff --git a/streaming/src/main/scala/org/apache/spark/streaming/Checkpoint.scala b/streaming/src/main/scala/org/apache/spark/streaming/Checkpoint.scala
index 5cc677d085..0395600954 100644
--- a/streaming/src/main/scala/org/apache/spark/streaming/Checkpoint.scala
+++ b/streaming/src/main/scala/org/apache/spark/streaming/Checkpoint.scala
@@ -247,10 +247,10 @@ class CheckpointWriter(
           // Delete old checkpoint files
           val allCheckpointFiles = Checkpoint.getCheckpointFiles(checkpointDir, Some(fs))
           if (allCheckpointFiles.size > 10) {
-            allCheckpointFiles.take(allCheckpointFiles.size - 10).foreach(file => {
+            allCheckpointFiles.take(allCheckpointFiles.size - 10).foreach { file =>
               logInfo("Deleting " + file)
               fs.delete(file, true)
-            })
+            }
           }
 
           // All done, print success
@@ -345,7 +345,7 @@ object CheckpointReader extends Logging {
     // Try to read the checkpoint files in the order
     logInfo("Checkpoint files found: " + checkpointFiles.mkString(","))
     var readError: Exception = null
-    checkpointFiles.foreach(file => {
+    checkpointFiles.foreach { file =>
       logInfo("Attempting to load checkpoint from file " + file)
       try {
         val fis = fs.open(file)
@@ -358,7 +358,7 @@ object CheckpointReader extends Logging {
           readError = e
           logWarning("Error reading checkpoint from file " + file, e)
       }
-    })
+    }
 
     // If none of checkpoint files could be read, then throw exception
     if (!ignoreReadError) {
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 28aed0ca45..8efb09a8ce 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
@@ -48,11 +48,11 @@ class StateDStream[K: ClassTag, V: ClassTag, S: ClassTag](
     // and then apply the update function
     val updateFuncLocal = updateFunc
     val finalFunc = (iterator: Iterator[(K, (Iterable[V], Iterable[S]))]) => {
-      val i = iterator.map(t => {
+      val i = iterator.map { t =>
         val itr = t._2._2.iterator
         val headOption = if (itr.hasNext) Some(itr.next()) else None
         (t._1, t._2._1.toSeq, headOption)
-      })
+      }
       updateFuncLocal(i)
     }
     val cogroupedRDD = parentRDD.cogroup(prevStateRDD, partitioner)
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 3b33a979df..9aa2f0bbb9 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
@@ -434,11 +434,11 @@ class ReceiverTracker(ssc: StreamingContext, skipReceiverLaunch: Boolean = false
    * worker nodes as a parallel collection, and runs them.
    */
   private def launchReceivers(): Unit = {
-    val receivers = receiverInputStreams.map(nis => {
+    val receivers = receiverInputStreams.map { nis =>
       val rcvr = nis.getReceiver()
       rcvr.setReceiverId(nis.id)
       rcvr
-    })
+    }
 
     runDummySparkJob()