Optimized imports

Optimized imports and arranged according to scala style guide @
https://cwiki.apache.org/confluence/display/SPARK/Spark+Code+Style+Guide#SparkCodeStyleGuide-Imports

Author: NirmalReddy <nirmal.reddy@imaginea.com>
Author: NirmalReddy <nirmal_reddy2000@yahoo.com>

Closes apache#613 from NirmalReddy/opt-imports and squashes the following commits:

578b4f5 [NirmalReddy] imported java.lang.Double as JDouble
a2cbcc5 [NirmalReddy] addressed the comments
776d664 [NirmalReddy] Optimized imports in core

Author: NirmalReddy

core/src/main/java/org/apache/spark/network/netty/FileClient.java

@@ -17,6 +17,8 @@
 
 package org.apache.spark.network.netty;
 
+import java.util.concurrent.TimeUnit;
+
 import io.netty.bootstrap.Bootstrap;
 import io.netty.channel.Channel;
 import io.netty.channel.ChannelOption;
@@ -27,8 +29,6 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import java.util.concurrent.TimeUnit;
-
 class FileClient {
 
   private static final Logger LOG = LoggerFactory.getLogger(FileClient.class.getName());

core/src/main/java/org/apache/spark/network/netty/FileServerHandler.java

@@ -23,11 +23,11 @@
 import io.netty.channel.ChannelHandlerContext;
 import io.netty.channel.SimpleChannelInboundHandler;
 import io.netty.channel.DefaultFileRegion;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import org.apache.spark.storage.BlockId;
 import org.apache.spark.storage.FileSegment;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
 
 class FileServerHandler extends SimpleChannelInboundHandler<String> {
 

core/src/main/scala/org/apache/hadoop/mapreduce/SparkHadoopMapReduceUtil.scala

@@ -17,7 +17,8 @@
 
 package org.apache.hadoop.mapreduce
 
-import java.lang.{Integer => JInteger, Boolean => JBoolean}
+import java.lang.{Boolean => JBoolean, Integer => JInteger}
+
 import org.apache.hadoop.conf.Configuration
 
 private[apache]

core/src/main/scala/org/apache/spark/Accumulators.scala

@@ -19,8 +19,9 @@ package org.apache.spark
 
 import java.io.{ObjectInputStream, Serializable}
 
-import scala.collection.mutable.Map
 import scala.collection.generic.Growable
+import scala.collection.mutable.Map
+
 import org.apache.spark.serializer.JavaSerializer
 
 /**

core/src/main/scala/org/apache/spark/BlockStoreShuffleFetcher.scala

@@ -20,12 +20,11 @@ package org.apache.spark
 import scala.collection.mutable.ArrayBuffer
 import scala.collection.mutable.HashMap
 
-import org.apache.spark.executor.{ShuffleReadMetrics, TaskMetrics}
+import org.apache.spark.executor.ShuffleReadMetrics
 import org.apache.spark.serializer.Serializer
 import org.apache.spark.storage.{BlockId, BlockManagerId, ShuffleBlockId}
 import org.apache.spark.util.CompletionIterator
 
-
 private[spark] class BlockStoreShuffleFetcher extends ShuffleFetcher with Logging {
 
   override def fetch[T](

core/src/main/scala/org/apache/spark/CacheManager.scala

@@ -18,9 +18,9 @@
 package org.apache.spark
 
 import scala.collection.mutable.{ArrayBuffer, HashSet}
-import org.apache.spark.storage.{BlockId, BlockManager, StorageLevel, RDDBlockId}
-import org.apache.spark.rdd.RDD
 
+import org.apache.spark.rdd.RDD
+import org.apache.spark.storage.{BlockManager, RDDBlockId, StorageLevel}
 
 /** Spark class responsible for passing RDDs split contents to the BlockManager and making
     sure a node doesn't load two copies of an RDD at once.

core/src/main/scala/org/apache/spark/FutureAction.scala

@@ -21,10 +21,8 @@ import scala.concurrent._
 import scala.concurrent.duration.Duration
 import scala.util.Try
 
-import org.apache.spark.scheduler.{JobSucceeded, JobWaiter}
-import org.apache.spark.scheduler.JobFailed
 import org.apache.spark.rdd.RDD
-
+import org.apache.spark.scheduler.{JobFailed, JobSucceeded, JobWaiter}
 
 /**
  * A future for the result of an action to support cancellation. This is an extension of the

core/src/main/scala/org/apache/spark/HttpFileServer.scala

@@ -17,8 +17,10 @@
 
 package org.apache.spark
 
-import java.io.{File}
+import java.io.File
+
 import com.google.common.io.Files
+
 import org.apache.spark.util.Utils
 
 private[spark] class HttpFileServer extends Logging {

core/src/main/scala/org/apache/spark/HttpServer.scala

@@ -18,14 +18,14 @@
 package org.apache.spark
 
 import java.io.File
-import java.net.InetAddress
 
 import org.eclipse.jetty.server.Server
 import org.eclipse.jetty.server.bio.SocketConnector
 import org.eclipse.jetty.server.handler.DefaultHandler
 import org.eclipse.jetty.server.handler.HandlerList
 import org.eclipse.jetty.server.handler.ResourceHandler
 import org.eclipse.jetty.util.thread.QueuedThreadPool
+
 import org.apache.spark.util.Utils
 
 /**

core/src/main/scala/org/apache/spark/MapOutputTracker.scala

@@ -22,7 +22,6 @@ import java.util.zip.{GZIPInputStream, GZIPOutputStream}
 
 import scala.collection.mutable.HashSet
 import scala.concurrent.Await
-import scala.concurrent.duration._
 
 import akka.actor._
 import akka.pattern.ask