diff --git a/core/src/main/scala/org/apache/spark/deploy/client/Client.scala b/core/src/main/scala/org/apache/spark/deploy/client/Client.scala
index f60e56d959634..d0d65ca72ad7c 100644
--- a/core/src/main/scala/org/apache/spark/deploy/client/Client.scala
+++ b/core/src/main/scala/org/apache/spark/deploy/client/Client.scala
@@ -104,8 +104,10 @@ private[spark] class Client(
       activeMasterUrl = url
       master = context.actorSelection(Master.toAkkaUrl(activeMasterUrl))
       masterAddress = activeMasterUrl match {
-        case Master.sparkUrlRegex(host, port) => Address("akka.tcp", Master.systemName, host, port.toInt)
-        case x => throw new SparkException("Invalid spark URL:"+x)
+        case Master.sparkUrlRegex(host, port) =>
+          Address("akka.tcp", Master.systemName, host, port.toInt)
+        case x =>
+          throw new SparkException("Invalid spark URL: " + x)
       }
     }
 
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 808b54c0af782..87531b6719e1b 100644
--- a/core/src/main/scala/org/apache/spark/deploy/worker/Worker.scala
+++ b/core/src/main/scala/org/apache/spark/deploy/worker/Worker.scala
@@ -138,8 +138,10 @@ private[spark] class Worker(
       activeMasterWebUiUrl = uiUrl
       master = context.actorSelection(Master.toAkkaUrl(activeMasterUrl))
       masterAddress = activeMasterUrl match {
-        case Master.sparkUrlRegex(_host, _port) => Address("akka.tcp", Master.systemName, _host, _port.toInt)
-        case x => throw new SparkException("Invalid spark URL:"+x)
+        case Master.sparkUrlRegex(_host, _port) =>
+          Address("akka.tcp", Master.systemName, _host, _port.toInt)
+        case x =>
+          throw new SparkException("Invalid spark URL: " + x)
       }
       connected = true
     }
diff --git a/core/src/main/scala/org/apache/spark/storage/BlockObjectWriter.scala b/core/src/main/scala/org/apache/spark/storage/BlockObjectWriter.scala
index df33f6bfb0bb1..b4451fc7b8e56 100644
--- a/core/src/main/scala/org/apache/spark/storage/BlockObjectWriter.scala
+++ b/core/src/main/scala/org/apache/spark/storage/BlockObjectWriter.scala
@@ -44,7 +44,7 @@ abstract class BlockObjectWriter(val blockId: BlockId) {
    * Flush the partial writes and commit them as a single atomic block. Return the
    * number of bytes written for this commit.
    */
-  def commit(): LongSpark
+  def commit(): Long
 
   /**
    * Reverts writes that haven't been flushed yet. Callers should invoke this function
diff --git a/core/src/main/scala/org/apache/spark/util/AkkaUtils.scala b/core/src/main/scala/org/apache/spark/util/AkkaUtils.scala
index 9f3f1632776b7..74133cef6c132 100644
--- a/core/src/main/scala/org/apache/spark/util/AkkaUtils.scala
+++ b/core/src/main/scala/org/apache/spark/util/AkkaUtils.scala
@@ -17,11 +17,8 @@
 
 package org.apache.spark.util
 
-import akka.actor.{IndestructibleActorSystem, ActorSystem, ExtendedActorSystem}
+import akka.actor.{ActorSystem, ExtendedActorSystem, IndestructibleActorSystem}
 import com.typesafe.config.ConfigFactory
-import scala.concurrent.duration._
-import scala.concurrent.Await
-import akka.remote.RemoteActorRefProvider
 
 /**
  * Various utility classes for working with Akka.
@@ -47,7 +44,8 @@ private[spark] object AkkaUtils {
     val akkaTimeout = System.getProperty("spark.akka.timeout", "100").toInt
 
     val akkaFrameSize = System.getProperty("spark.akka.frameSize", "10").toInt
-    val lifecycleEvents = if (System.getProperty("spark.akka.logLifecycleEvents", "false").toBoolean) "on" else "off"
+    val lifecycleEvents =
+      if (System.getProperty("spark.akka.logLifecycleEvents", "false").toBoolean) "on" else "off"
 
     val akkaHeartBeatPauses = System.getProperty("spark.akka.heartbeat.pauses", "600").toInt
     val akkaFailureDetector =