diff --git a/core/src/main/scala/spark/Accumulators.scala b/core/src/main/scala/spark/Accumulators.scala
index c157cc8feb..cd8e43f556 100644
--- a/core/src/main/scala/spark/Accumulators.scala
+++ b/core/src/main/scala/spark/Accumulators.scala
@@ -18,7 +18,7 @@ import scala.collection.generic.Growable
  * @tparam R the full accumulated data
  * @tparam T partial data that can be added in
  */
-class Accumulable[R, T] (
+private[spark] class Accumulable[R, T] (
     @transient initialValue: R,
     param: AccumulableParam[R, T])
   extends Serializable {
@@ -73,7 +73,7 @@ class Accumulable[R, T] (
  * @tparam R the full accumulated data
  * @tparam T partial data that can be added in
  */
-trait AccumulableParam[R, T] extends Serializable {
+private[spark] trait AccumulableParam[R, T] extends Serializable {
   /**
    * Add additional data to the accumulator value.
    * @param r the current value of the accumulator
@@ -93,7 +93,7 @@ trait AccumulableParam[R, T] extends Serializable {
   def zero(initialValue: R): R
 }
 
-class GrowableAccumulableParam[R <% Growable[T] with TraversableOnce[T] with Serializable, T]
+private[spark] class GrowableAccumulableParam[R <% Growable[T] with TraversableOnce[T] with Serializable, T]
   extends AccumulableParam[R,T] {
 
   def addAccumulator(growable: R, elem: T) : R = {
@@ -124,7 +124,7 @@ class GrowableAccumulableParam[R <% Growable[T] with TraversableOnce[T] with Ser
  * @param param helper object defining how to add elements of type `T`
  * @tparam T result type
  */
-class Accumulator[T](
+private[spark] class Accumulator[T](
   @transient initialValue: T,
   param: AccumulatorParam[T]) extends Accumulable[T,T](initialValue, param)
 
@@ -133,7 +133,7 @@ class Accumulator[T](
  * as the accumulated value
  * @tparam T type of value to accumulate
  */
-trait AccumulatorParam[T] extends AccumulableParam[T, T] {
+private[spark] trait AccumulatorParam[T] extends AccumulableParam[T, T] {
   def addAccumulator(t1: T, t2: T) : T = {
     addInPlace(t1, t2)
   }
diff --git a/core/src/main/scala/spark/BlockRDD.scala b/core/src/main/scala/spark/BlockRDD.scala
index daabc0d566..faa99fe3e9 100644
--- a/core/src/main/scala/spark/BlockRDD.scala
+++ b/core/src/main/scala/spark/BlockRDD.scala
@@ -2,7 +2,7 @@ package spark
 
 import scala.collection.mutable.HashMap
 
-class BlockRDDSplit(val blockId: String, idx: Int) extends Split {
+private[spark] class BlockRDDSplit(val blockId: String, idx: Int) extends Split {
   val index = idx
 }
 
diff --git a/core/src/main/scala/spark/BlockStoreShuffleFetcher.scala b/core/src/main/scala/spark/BlockStoreShuffleFetcher.scala
index 9c42e88b68..fb65ba421a 100644
--- a/core/src/main/scala/spark/BlockStoreShuffleFetcher.scala
+++ b/core/src/main/scala/spark/BlockStoreShuffleFetcher.scala
@@ -11,8 +11,7 @@ import spark.storage.BlockManagerId
 
 import it.unimi.dsi.fastutil.io.FastBufferedInputStream
 
-
-class BlockStoreShuffleFetcher extends ShuffleFetcher with Logging {
+private[spark] class BlockStoreShuffleFetcher extends ShuffleFetcher with Logging {
   def fetch[K, V](shuffleId: Int, reduceId: Int, func: (K, V) => Unit) {
     logDebug("Fetching outputs for shuffle %d, reduce %d".format(shuffleId, reduceId))
     val blockManager = SparkEnv.get.blockManager
diff --git a/core/src/main/scala/spark/BoundedMemoryCache.scala b/core/src/main/scala/spark/BoundedMemoryCache.scala
index 6fe0b94297..e8392a194f 100644
--- a/core/src/main/scala/spark/BoundedMemoryCache.scala
+++ b/core/src/main/scala/spark/BoundedMemoryCache.scala
@@ -9,7 +9,7 @@ import java.util.LinkedHashMap
  * some cache entries have pointers to a shared object. Nonetheless, this Cache should work well
  * when most of the space is used by arrays of primitives or of simple classes.
  */
-class BoundedMemoryCache(maxBytes: Long) extends Cache with Logging {
+private[spark] class BoundedMemoryCache(maxBytes: Long) extends Cache with Logging {
   logInfo("BoundedMemoryCache.maxBytes = " + maxBytes)
 
   def this() {
@@ -104,9 +104,9 @@ class BoundedMemoryCache(maxBytes: Long) extends Cache with Logging {
 }
 
 // An entry in our map; stores a cached object and its size in bytes
-case class Entry(value: Any, size: Long)
+private[spark] case class Entry(value: Any, size: Long)
 
-object BoundedMemoryCache {
+private[spark] object BoundedMemoryCache {
   /**
    * Get maximum cache capacity from system configuration
    */
diff --git a/core/src/main/scala/spark/Cache.scala b/core/src/main/scala/spark/Cache.scala
index 150fe14e2c..20d677a854 100644
--- a/core/src/main/scala/spark/Cache.scala
+++ b/core/src/main/scala/spark/Cache.scala
@@ -2,9 +2,9 @@ package spark
 
 import java.util.concurrent.atomic.AtomicInteger
 
-sealed trait CachePutResponse
-case class CachePutSuccess(size: Long) extends CachePutResponse
-case class CachePutFailure() extends CachePutResponse
+private[spark] sealed trait CachePutResponse
+private[spark] case class CachePutSuccess(size: Long) extends CachePutResponse
+private[spark] case class CachePutFailure() extends CachePutResponse
 
 /**
  * An interface for caches in Spark, to allow for multiple implementations. Caches are used to store
@@ -22,7 +22,7 @@ case class CachePutFailure() extends CachePutResponse
  * This abstract class handles the creation of key spaces, so that subclasses need only deal with
  * keys that are unique across modules.
  */
-abstract class Cache {
+private[spark] abstract class Cache {
   private val nextKeySpaceId = new AtomicInteger(0)
   private def newKeySpaceId() = nextKeySpaceId.getAndIncrement()
 
@@ -52,7 +52,7 @@ abstract class Cache {
 /**
  * A key namespace in a Cache.
  */
-class KeySpace(cache: Cache, val keySpaceId: Int) {
+private[spark] class KeySpace(cache: Cache, val keySpaceId: Int) {
   def get(datasetId: Any, partition: Int): Any =
     cache.get((keySpaceId, datasetId), partition)
 
diff --git a/core/src/main/scala/spark/CacheTracker.scala b/core/src/main/scala/spark/CacheTracker.scala
index d9e0ef90b8..9a23f9e7cc 100644
--- a/core/src/main/scala/spark/CacheTracker.scala
+++ b/core/src/main/scala/spark/CacheTracker.scala
@@ -15,19 +15,20 @@ import scala.collection.mutable.HashSet
 import spark.storage.BlockManager
 import spark.storage.StorageLevel
 
-sealed trait CacheTrackerMessage
-case class AddedToCache(rddId: Int, partition: Int, host: String, size: Long = 0L)
-  extends CacheTrackerMessage
-case class DroppedFromCache(rddId: Int, partition: Int, host: String, size: Long = 0L)
-  extends CacheTrackerMessage
-case class MemoryCacheLost(host: String) extends CacheTrackerMessage
-case class RegisterRDD(rddId: Int, numPartitions: Int) extends CacheTrackerMessage
-case class SlaveCacheStarted(host: String, size: Long) extends CacheTrackerMessage
-case object GetCacheStatus extends CacheTrackerMessage
-case object GetCacheLocations extends CacheTrackerMessage
-case object StopCacheTracker extends CacheTrackerMessage
+private[spark] sealed trait CacheTrackerMessage
 
-class CacheTrackerActor extends Actor with Logging {
+private[spark] case class AddedToCache(rddId: Int, partition: Int, host: String, size: Long = 0L)
+  extends CacheTrackerMessage
+private[spark] case class DroppedFromCache(rddId: Int, partition: Int, host: String, size: Long = 0L)
+  extends CacheTrackerMessage
+private[spark] case class MemoryCacheLost(host: String) extends CacheTrackerMessage
+private[spark] case class RegisterRDD(rddId: Int, numPartitions: Int) extends CacheTrackerMessage
+private[spark] case class SlaveCacheStarted(host: String, size: Long) extends CacheTrackerMessage
+private[spark] case object GetCacheStatus extends CacheTrackerMessage
+private[spark] case object GetCacheLocations extends CacheTrackerMessage
+private[spark] case object StopCacheTracker extends CacheTrackerMessage
+
+private[spark] class CacheTrackerActor extends Actor with Logging {
   // TODO: Should probably store (String, CacheType) tuples
   private val locs = new HashMap[Int, Array[List[String]]]
 
@@ -89,7 +90,7 @@ class CacheTrackerActor extends Actor with Logging {
   }
 }
 
-class CacheTracker(actorSystem: ActorSystem, isMaster: Boolean, blockManager: BlockManager)
+private[spark] class CacheTracker(actorSystem: ActorSystem, isMaster: Boolean, blockManager: BlockManager)
   extends Logging {
  
   // Tracker actor on the master, or remote reference to it on workers
diff --git a/core/src/main/scala/spark/CartesianRDD.scala b/core/src/main/scala/spark/CartesianRDD.scala
index e26041555a..9f94bcb413 100644
--- a/core/src/main/scala/spark/CartesianRDD.scala
+++ b/core/src/main/scala/spark/CartesianRDD.scala
@@ -1,6 +1,6 @@
 package spark
 
-class CartesianSplit(idx: Int, val s1: Split, val s2: Split) extends Split with Serializable {
+private[spark] class CartesianSplit(idx: Int, val s1: Split, val s2: Split) extends Split with Serializable {
   override val index: Int = idx
 }
 
diff --git a/core/src/main/scala/spark/ClosureCleaner.scala b/core/src/main/scala/spark/ClosureCleaner.scala
index 3b83d23a13..98525b99c8 100644
--- a/core/src/main/scala/spark/ClosureCleaner.scala
+++ b/core/src/main/scala/spark/ClosureCleaner.scala
@@ -9,7 +9,7 @@ import org.objectweb.asm.{ClassReader, MethodVisitor, Type}
 import org.objectweb.asm.commons.EmptyVisitor
 import org.objectweb.asm.Opcodes._
 
-object ClosureCleaner extends Logging {
+private[spark] object ClosureCleaner extends Logging {
   // Get an ASM class reader for a given class from the JAR that loaded it
   private def getClassReader(cls: Class[_]): ClassReader = {
     new ClassReader(cls.getResourceAsStream(
@@ -154,7 +154,7 @@ object ClosureCleaner extends Logging {
   }
 }
 
-class FieldAccessFinder(output: Map[Class[_], Set[String]]) extends EmptyVisitor {
+private[spark] class FieldAccessFinder(output: Map[Class[_], Set[String]]) extends EmptyVisitor {
   override def visitMethod(access: Int, name: String, desc: String,
       sig: String, exceptions: Array[String]): MethodVisitor = {
     return new EmptyVisitor {
@@ -180,7 +180,7 @@ class FieldAccessFinder(output: Map[Class[_], Set[String]]) extends EmptyVisitor
   }
 }
 
-class InnerClosureFinder(output: Set[Class[_]]) extends EmptyVisitor {
+private[spark] class InnerClosureFinder(output: Set[Class[_]]) extends EmptyVisitor {
   var myName: String = null
   
   override def visit(version: Int, access: Int, name: String, sig: String,
diff --git a/core/src/main/scala/spark/CoGroupedRDD.scala b/core/src/main/scala/spark/CoGroupedRDD.scala
index 6959917d14..2c270766f9 100644
--- a/core/src/main/scala/spark/CoGroupedRDD.scala
+++ b/core/src/main/scala/spark/CoGroupedRDD.scala
@@ -6,16 +6,16 @@ import java.io.ObjectInputStream
 import scala.collection.mutable.ArrayBuffer
 import scala.collection.mutable.HashMap
 
-sealed trait CoGroupSplitDep extends Serializable
-case class NarrowCoGroupSplitDep(rdd: RDD[_], split: Split) extends CoGroupSplitDep
-case class ShuffleCoGroupSplitDep(shuffleId: Int) extends CoGroupSplitDep
+private[spark] sealed trait CoGroupSplitDep extends Serializable
+private[spark] case class NarrowCoGroupSplitDep(rdd: RDD[_], split: Split) extends CoGroupSplitDep
+private[spark] case class ShuffleCoGroupSplitDep(shuffleId: Int) extends CoGroupSplitDep
 
-class CoGroupSplit(idx: Int, val deps: Seq[CoGroupSplitDep]) extends Split with Serializable {
+private[spark] class CoGroupSplit(idx: Int, val deps: Seq[CoGroupSplitDep]) extends Split with Serializable {
   override val index: Int = idx
   override def hashCode(): Int = idx
 }
 
-class CoGroupAggregator
+private[spark] class CoGroupAggregator
   extends Aggregator[Any, Any, ArrayBuffer[Any]](
     { x => ArrayBuffer(x) },
     { (b, x) => b += x },
diff --git a/core/src/main/scala/spark/Dependency.scala b/core/src/main/scala/spark/Dependency.scala
index c0ff94acc6..a478710f04 100644
--- a/core/src/main/scala/spark/Dependency.scala
+++ b/core/src/main/scala/spark/Dependency.scala
@@ -1,23 +1,23 @@
 package spark
 
-abstract class Dependency[T](val rdd: RDD[T], val isShuffle: Boolean) extends Serializable
+private[spark] abstract class Dependency[T](val rdd: RDD[T], val isShuffle: Boolean) extends Serializable
 
-abstract class NarrowDependency[T](rdd: RDD[T]) extends Dependency(rdd, false) {
+private[spark] abstract class NarrowDependency[T](rdd: RDD[T]) extends Dependency(rdd, false) {
   def getParents(outputPartition: Int): Seq[Int]
 }
 
-class ShuffleDependency[K, V, C](
+private[spark] class ShuffleDependency[K, V, C](
     val shuffleId: Int,
     @transient rdd: RDD[(K, V)],
     val aggregator: Aggregator[K, V, C],
     val partitioner: Partitioner)
   extends Dependency(rdd, true)
 
-class OneToOneDependency[T](rdd: RDD[T]) extends NarrowDependency[T](rdd) {
+private[spark] class OneToOneDependency[T](rdd: RDD[T]) extends NarrowDependency[T](rdd) {
   override def getParents(partitionId: Int) = List(partitionId)
 }
 
-class RangeDependency[T](rdd: RDD[T], inStart: Int, outStart: Int, length: Int)
+private[spark] class RangeDependency[T](rdd: RDD[T], inStart: Int, outStart: Int, length: Int)
   extends NarrowDependency[T](rdd) {
   
   override def getParents(partitionId: Int) = {
diff --git a/core/src/main/scala/spark/DoubleRDDFunctions.scala b/core/src/main/scala/spark/DoubleRDDFunctions.scala
index 1fbf66b7de..6252dc44f7 100644
--- a/core/src/main/scala/spark/DoubleRDDFunctions.scala
+++ b/core/src/main/scala/spark/DoubleRDDFunctions.scala
@@ -10,7 +10,7 @@ import spark.util.StatCounter
 /**
  * Extra functions available on RDDs of Doubles through an implicit conversion.
  */
-class DoubleRDDFunctions(self: RDD[Double]) extends Logging with Serializable {
+private[spark] class DoubleRDDFunctions(self: RDD[Double]) extends Logging with Serializable {
   def sum(): Double = {
     self.reduce(_ + _)
   }
diff --git a/core/src/main/scala/spark/FetchFailedException.scala b/core/src/main/scala/spark/FetchFailedException.scala
index 55512f4481..a953081d24 100644
--- a/core/src/main/scala/spark/FetchFailedException.scala
+++ b/core/src/main/scala/spark/FetchFailedException.scala
@@ -2,7 +2,7 @@ package spark
 
 import spark.storage.BlockManagerId
 
-class FetchFailedException(
+private[spark] class FetchFailedException(
     val bmAddress: BlockManagerId,
     val shuffleId: Int,
     val mapId: Int,
diff --git a/core/src/main/scala/spark/HadoopRDD.scala b/core/src/main/scala/spark/HadoopRDD.scala
index 0befca582d..6d448116a9 100644
--- a/core/src/main/scala/spark/HadoopRDD.scala
+++ b/core/src/main/scala/spark/HadoopRDD.scala
@@ -18,7 +18,7 @@ import org.apache.hadoop.util.ReflectionUtils
 /** 
  * A Spark split class that wraps around a Hadoop InputSplit.
  */
-class HadoopSplit(rddId: Int, idx: Int, @transient s: InputSplit)
+private[spark] class HadoopSplit(rddId: Int, idx: Int, @transient s: InputSplit)
   extends Split
   with Serializable {
   
diff --git a/core/src/main/scala/spark/HttpFileServer.scala b/core/src/main/scala/spark/HttpFileServer.scala
index 05ca846c85..659d17718f 100644
--- a/core/src/main/scala/spark/HttpFileServer.scala
+++ b/core/src/main/scala/spark/HttpFileServer.scala
@@ -5,7 +5,7 @@ import java.net.URL
 import scala.collection.mutable.HashMap
 import org.apache.hadoop.fs.FileUtil
 
-class HttpFileServer extends Logging {
+private[spark] class HttpFileServer extends Logging {
   
   var baseDir : File = null
   var fileDir : File = null
diff --git a/core/src/main/scala/spark/HttpServer.scala b/core/src/main/scala/spark/HttpServer.scala
index 855f2c752f..0196595ba1 100644
--- a/core/src/main/scala/spark/HttpServer.scala
+++ b/core/src/main/scala/spark/HttpServer.scala
@@ -12,14 +12,14 @@ import org.eclipse.jetty.util.thread.QueuedThreadPool
 /**
  * Exception type thrown by HttpServer when it is in the wrong state for an operation.
  */
-class ServerStateException(message: String) extends Exception(message)
+private[spark] class ServerStateException(message: String) extends Exception(message)
 
 /**
  * An HTTP server for static content used to allow worker nodes to access JARs added to SparkContext
  * as well as classes created by the interpreter when the user types in code. This is just a wrapper
  * around a Jetty server.
  */
-class HttpServer(resourceBase: File) extends Logging {
+private[spark] class HttpServer(resourceBase: File) extends Logging {
   private var server: Server = null
   private var port: Int = -1
 
diff --git a/core/src/main/scala/spark/JavaSerializer.scala b/core/src/main/scala/spark/JavaSerializer.scala
index 1511c2620e..39d554b6a5 100644
--- a/core/src/main/scala/spark/JavaSerializer.scala
+++ b/core/src/main/scala/spark/JavaSerializer.scala
@@ -5,14 +5,14 @@ import java.nio.ByteBuffer
 
 import spark.util.ByteBufferInputStream
 
-class JavaSerializationStream(out: OutputStream) extends SerializationStream {
+private[spark] class JavaSerializationStream(out: OutputStream) extends SerializationStream {
   val objOut = new ObjectOutputStream(out)
   def writeObject[T](t: T): SerializationStream = { objOut.writeObject(t); this }
   def flush() { objOut.flush() }
   def close() { objOut.close() }
 }
 
-class JavaDeserializationStream(in: InputStream, loader: ClassLoader)
+private[spark] class JavaDeserializationStream(in: InputStream, loader: ClassLoader)
 extends DeserializationStream {
   val objIn = new ObjectInputStream(in) {
     override def resolveClass(desc: ObjectStreamClass) =
@@ -23,7 +23,7 @@ extends DeserializationStream {
   def close() { objIn.close() }
 }
 
-class JavaSerializerInstance extends SerializerInstance {
+private[spark] class JavaSerializerInstance extends SerializerInstance {
   def serialize[T](t: T): ByteBuffer = {
     val bos = new ByteArrayOutputStream()
     val out = serializeStream(bos)
@@ -57,6 +57,6 @@ class JavaSerializerInstance extends SerializerInstance {
   }
 }
 
-class JavaSerializer extends Serializer {
+private[spark] class JavaSerializer extends Serializer {
   def newInstance(): SerializerInstance = new JavaSerializerInstance
 }
diff --git a/core/src/main/scala/spark/KryoSerializer.scala b/core/src/main/scala/spark/KryoSerializer.scala
index 376fcff4c8..1e55621b8e 100644
--- a/core/src/main/scala/spark/KryoSerializer.scala
+++ b/core/src/main/scala/spark/KryoSerializer.scala
@@ -20,7 +20,7 @@ import spark.storage._
  * Zig-zag encoder used to write object sizes to serialization streams.
  * Based on Kryo's integer encoder.
  */
-object ZigZag {
+private[spark] object ZigZag {
   def writeInt(n: Int, out: OutputStream) {
     var value = n
     if ((value & ~0x7F) == 0) {
@@ -68,7 +68,7 @@ object ZigZag {
   }
 }
 
-class KryoSerializationStream(kryo: Kryo, threadBuffer: ByteBuffer, out: OutputStream)
+private[spark] class KryoSerializationStream(kryo: Kryo, threadBuffer: ByteBuffer, out: OutputStream)
 extends SerializationStream {
   val channel = Channels.newChannel(out)
 
@@ -85,7 +85,7 @@ extends SerializationStream {
   def close() { out.close() }
 }
 
-class KryoDeserializationStream(objectBuffer: ObjectBuffer, in: InputStream)
+private[spark] class KryoDeserializationStream(objectBuffer: ObjectBuffer, in: InputStream)
 extends DeserializationStream {
   def readObject[T](): T = {
     val len = ZigZag.readInt(in)
@@ -95,7 +95,7 @@ extends DeserializationStream {
   def close() { in.close() }
 }
 
-class KryoSerializerInstance(ks: KryoSerializer) extends SerializerInstance {
+private[spark] class KryoSerializerInstance(ks: KryoSerializer) extends SerializerInstance {
   val kryo = ks.kryo
   val threadBuffer = ks.threadBuffer.get()
   val objectBuffer = ks.objectBuffer.get()
diff --git a/core/src/main/scala/spark/MapOutputTracker.scala b/core/src/main/scala/spark/MapOutputTracker.scala
index 82c1391345..116d526854 100644
--- a/core/src/main/scala/spark/MapOutputTracker.scala
+++ b/core/src/main/scala/spark/MapOutputTracker.scala
@@ -16,11 +16,11 @@ import scala.collection.mutable.HashSet
 
 import spark.storage.BlockManagerId
 
-sealed trait MapOutputTrackerMessage
-case class GetMapOutputLocations(shuffleId: Int) extends MapOutputTrackerMessage 
-case object StopMapOutputTracker extends MapOutputTrackerMessage
+private[spark] sealed trait MapOutputTrackerMessage
+private[spark] case class GetMapOutputLocations(shuffleId: Int) extends MapOutputTrackerMessage 
+private[spark] case object StopMapOutputTracker extends MapOutputTrackerMessage
 
-class MapOutputTrackerActor(tracker: MapOutputTracker) extends Actor with Logging {
+private[spark] class MapOutputTrackerActor(tracker: MapOutputTracker) extends Actor with Logging {
   def receive = {
     case GetMapOutputLocations(shuffleId: Int) =>
       logInfo("Asked to get map output locations for shuffle " + shuffleId)
@@ -33,7 +33,7 @@ class MapOutputTrackerActor(tracker: MapOutputTracker) extends Actor with Loggin
   }
 }
 
-class MapOutputTracker(actorSystem: ActorSystem, isMaster: Boolean) extends Logging {
+private[spark] class MapOutputTracker(actorSystem: ActorSystem, isMaster: Boolean) extends Logging {
   val ip: String = System.getProperty("spark.master.host", "localhost")
   val port: Int = System.getProperty("spark.master.port", "7077").toInt
   val actorName: String = "MapOutputTracker"
diff --git a/core/src/main/scala/spark/NewHadoopRDD.scala b/core/src/main/scala/spark/NewHadoopRDD.scala
index 14f708a3f8..9c5ad3511e 100644
--- a/core/src/main/scala/spark/NewHadoopRDD.scala
+++ b/core/src/main/scala/spark/NewHadoopRDD.scala
@@ -13,7 +13,7 @@ import org.apache.hadoop.mapreduce.TaskAttemptID
 import java.util.Date
 import java.text.SimpleDateFormat
 
-class NewHadoopSplit(rddId: Int, val index: Int, @transient rawSplit: InputSplit with Writable)
+private[spark] class NewHadoopSplit(rddId: Int, val index: Int, @transient rawSplit: InputSplit with Writable)
   extends Split {
   
   val serializableHadoopSplit = new SerializableWritable(rawSplit)
diff --git a/core/src/main/scala/spark/PairRDDFunctions.scala b/core/src/main/scala/spark/PairRDDFunctions.scala
index 4752bf8d9f..57fdb741df 100644
--- a/core/src/main/scala/spark/PairRDDFunctions.scala
+++ b/core/src/main/scala/spark/PairRDDFunctions.scala
@@ -41,7 +41,7 @@ import spark.partial.PartialResult
 /**
  * Extra functions available on RDDs of (key, value) pairs through an implicit conversion.
  */
-class PairRDDFunctions[K: ClassManifest, V: ClassManifest](
+private[spark] class PairRDDFunctions[K: ClassManifest, V: ClassManifest](
     self: RDD[(K, V)])
   extends Logging
   with Serializable {
@@ -430,7 +430,7 @@ class PairRDDFunctions[K: ClassManifest, V: ClassManifest](
   def getValueClass() = implicitly[ClassManifest[V]].erasure
 }
 
-class OrderedRDDFunctions[K <% Ordered[K]: ClassManifest, V: ClassManifest](
+private[spark] class OrderedRDDFunctions[K <% Ordered[K]: ClassManifest, V: ClassManifest](
   self: RDD[(K, V)])
   extends Logging
   with Serializable {
@@ -459,6 +459,6 @@ class FlatMappedValuesRDD[K, V, U](prev: RDD[(K, V)], f: V => TraversableOnce[U]
   }
 }
 
-object Manifests {
+private[spark] object Manifests {
   val seqSeqManifest = classManifest[Seq[Seq[_]]]
 }
diff --git a/core/src/main/scala/spark/ParallelCollection.scala b/core/src/main/scala/spark/ParallelCollection.scala
index d79007ab40..321f5264b8 100644
--- a/core/src/main/scala/spark/ParallelCollection.scala
+++ b/core/src/main/scala/spark/ParallelCollection.scala
@@ -3,7 +3,7 @@ package spark
 import scala.collection.immutable.NumericRange
 import scala.collection.mutable.ArrayBuffer
 
-class ParallelCollectionSplit[T: ClassManifest](
+private[spark] class ParallelCollectionSplit[T: ClassManifest](
     val rddId: Long,
     val slice: Int,
     values: Seq[T])
diff --git a/core/src/main/scala/spark/SampledRDD.scala b/core/src/main/scala/spark/SampledRDD.scala
index c066017e89..4b33148364 100644
--- a/core/src/main/scala/spark/SampledRDD.scala
+++ b/core/src/main/scala/spark/SampledRDD.scala
@@ -4,7 +4,7 @@ import java.util.Random
 import cern.jet.random.Poisson
 import cern.jet.random.engine.DRand
 
-class SampledRDDSplit(val prev: Split, val seed: Int) extends Split with Serializable {
+private[spark] class SampledRDDSplit(val prev: Split, val seed: Int) extends Split with Serializable {
   override val index: Int = prev.index
 }
 
diff --git a/core/src/main/scala/spark/SequenceFileRDDFunctions.scala b/core/src/main/scala/spark/SequenceFileRDDFunctions.scala
index ea7171d3a1..6224e957e5 100644
--- a/core/src/main/scala/spark/SequenceFileRDDFunctions.scala
+++ b/core/src/main/scala/spark/SequenceFileRDDFunctions.scala
@@ -30,7 +30,7 @@ import SparkContext._
  * through an implicit conversion. Note that this can't be part of PairRDDFunctions because
  * we need more implicit parameters to convert our keys and values to Writable.
  */
-class SequenceFileRDDFunctions[K <% Writable: ClassManifest, V <% Writable : ClassManifest](
+private[spark] class SequenceFileRDDFunctions[K <% Writable: ClassManifest, V <% Writable : ClassManifest](
     self: RDD[(K, V)])
   extends Logging
   with Serializable {
diff --git a/core/src/main/scala/spark/Serializer.scala b/core/src/main/scala/spark/Serializer.scala
index 9ec07cc173..c0e08289d8 100644
--- a/core/src/main/scala/spark/Serializer.scala
+++ b/core/src/main/scala/spark/Serializer.scala
@@ -12,14 +12,14 @@ import spark.util.ByteBufferInputStream
  * A serializer. Because some serialization libraries are not thread safe, this class is used to 
  * create SerializerInstances that do the actual serialization.
  */
-trait Serializer {
+private[spark] trait Serializer {
   def newInstance(): SerializerInstance
 }
 
 /**
  * An instance of the serializer, for use by one thread at a time.
  */
-trait SerializerInstance {
+private[spark] trait SerializerInstance {
   def serialize[T](t: T): ByteBuffer
 
   def deserialize[T](bytes: ByteBuffer): T
@@ -50,7 +50,7 @@ trait SerializerInstance {
 /**
  * A stream for writing serialized objects.
  */
-trait SerializationStream {
+private[spark] trait SerializationStream {
   def writeObject[T](t: T): SerializationStream
   def flush(): Unit
   def close(): Unit
@@ -66,7 +66,7 @@ trait SerializationStream {
 /**
  * A stream for reading serialized objects.
  */
-trait DeserializationStream {
+private[spark] trait DeserializationStream {
   def readObject[T](): T
   def close(): Unit
 
diff --git a/core/src/main/scala/spark/ShuffleFetcher.scala b/core/src/main/scala/spark/ShuffleFetcher.scala
index 4f8d98f7d0..daa35fe7f2 100644
--- a/core/src/main/scala/spark/ShuffleFetcher.scala
+++ b/core/src/main/scala/spark/ShuffleFetcher.scala
@@ -1,6 +1,6 @@
 package spark
 
-abstract class ShuffleFetcher {
+private[spark] abstract class ShuffleFetcher {
   // Fetch the shuffle outputs for a given ShuffleDependency, calling func exactly
   // once on each key-value pair obtained.
   def fetch[K, V](shuffleId: Int, reduceId: Int, func: (K, V) => Unit)
diff --git a/core/src/main/scala/spark/ShuffledRDD.scala b/core/src/main/scala/spark/ShuffledRDD.scala
index 11d5c0ede8..1a9f4cfec3 100644
--- a/core/src/main/scala/spark/ShuffledRDD.scala
+++ b/core/src/main/scala/spark/ShuffledRDD.scala
@@ -4,7 +4,7 @@ import scala.collection.mutable.ArrayBuffer
 import java.util.{HashMap => JHashMap}
 
 
-class ShuffledRDDSplit(val idx: Int) extends Split {
+private[spark] class ShuffledRDDSplit(val idx: Int) extends Split {
   override val index = idx
   override def hashCode(): Int = idx
 }
diff --git a/core/src/main/scala/spark/SizeEstimator.scala b/core/src/main/scala/spark/SizeEstimator.scala
index 6a71522922..7c3e8640e9 100644
--- a/core/src/main/scala/spark/SizeEstimator.scala
+++ b/core/src/main/scala/spark/SizeEstimator.scala
@@ -22,7 +22,7 @@ import it.unimi.dsi.fastutil.ints.IntOpenHashSet
  * Based on the following JavaWorld article:
  * http://www.javaworld.com/javaworld/javaqa/2003-12/02-qa-1226-sizeof.html
  */
-object SizeEstimator extends Logging {
+private[spark] object SizeEstimator extends Logging {
 
   // Sizes of primitive types
   private val BYTE_SIZE    = 1
diff --git a/core/src/main/scala/spark/SoftReferenceCache.scala b/core/src/main/scala/spark/SoftReferenceCache.scala
index ce9370c5d7..3dd0a4b1f9 100644
--- a/core/src/main/scala/spark/SoftReferenceCache.scala
+++ b/core/src/main/scala/spark/SoftReferenceCache.scala
@@ -5,7 +5,7 @@ import com.google.common.collect.MapMaker
 /**
  * An implementation of Cache that uses soft references.
  */
-class SoftReferenceCache extends Cache {
+private[spark] class SoftReferenceCache extends Cache {
   val map = new MapMaker().softValues().makeMap[Any, Any]()
 
   override def get(datasetId: Any, partition: Int): Any =
diff --git a/core/src/main/scala/spark/SparkContext.scala b/core/src/main/scala/spark/SparkContext.scala
index 79a9e8e34e..5742e64b56 100644
--- a/core/src/main/scala/spark/SparkContext.scala
+++ b/core/src/main/scala/spark/SparkContext.scala
@@ -589,7 +589,7 @@ object SparkContext {
  * that doesn't know the type of T when it is created. This sounds strange but is necessary to
  * support converting subclasses of Writable to themselves (writableWritableConverter).
  */
-class WritableConverter[T](
+private[spark] class WritableConverter[T](
     val writableClass: ClassManifest[T] => Class[_ <: Writable],
     val convert: Writable => T)
   extends Serializable
diff --git a/core/src/main/scala/spark/TaskEndReason.scala b/core/src/main/scala/spark/TaskEndReason.scala
index 6e4eb25ed4..3e5668892f 100644
--- a/core/src/main/scala/spark/TaskEndReason.scala
+++ b/core/src/main/scala/spark/TaskEndReason.scala
@@ -7,10 +7,10 @@ import spark.storage.BlockManagerId
  * tasks several times for "ephemeral" failures, and only report back failures that require some
  * old stages to be resubmitted, such as shuffle map fetch failures.
  */
-sealed trait TaskEndReason
+private[spark] sealed trait TaskEndReason
 
-case object Success extends TaskEndReason
-case object Resubmitted extends TaskEndReason // Task was finished earlier but we've now lost it
-case class FetchFailed(bmAddress: BlockManagerId, shuffleId: Int, mapId: Int, reduceId: Int) extends TaskEndReason
-case class ExceptionFailure(exception: Throwable) extends TaskEndReason
-case class OtherFailure(message: String) extends TaskEndReason
+private[spark] case object Success extends TaskEndReason
+private[spark] case object Resubmitted extends TaskEndReason // Task was finished earlier but we've now lost it
+private[spark] case class FetchFailed(bmAddress: BlockManagerId, shuffleId: Int, mapId: Int, reduceId: Int) extends TaskEndReason
+private[spark] case class ExceptionFailure(exception: Throwable) extends TaskEndReason
+private[spark] case class OtherFailure(message: String) extends TaskEndReason
diff --git a/core/src/main/scala/spark/TaskState.scala b/core/src/main/scala/spark/TaskState.scala
index 9566b52432..78eb33a628 100644
--- a/core/src/main/scala/spark/TaskState.scala
+++ b/core/src/main/scala/spark/TaskState.scala
@@ -2,7 +2,7 @@ package spark
 
 import org.apache.mesos.Protos.{TaskState => MesosTaskState}
 
-object TaskState
+private[spark] object TaskState
   extends Enumeration("LAUNCHING", "RUNNING", "FINISHED", "FAILED", "KILLED", "LOST") {
 
   val LAUNCHING, RUNNING, FINISHED, FAILED, KILLED, LOST = Value
diff --git a/core/src/main/scala/spark/UnionRDD.scala b/core/src/main/scala/spark/UnionRDD.scala
index 0e8164d6ab..3e795ea2a2 100644
--- a/core/src/main/scala/spark/UnionRDD.scala
+++ b/core/src/main/scala/spark/UnionRDD.scala
@@ -2,7 +2,7 @@ package spark
 
 import scala.collection.mutable.ArrayBuffer
 
-class UnionSplit[T: ClassManifest](
+private[spark] class UnionSplit[T: ClassManifest](
     idx: Int, 
     rdd: RDD[T],
     split: Split)
diff --git a/core/src/main/scala/spark/broadcast/BitTorrentBroadcast.scala b/core/src/main/scala/spark/broadcast/BitTorrentBroadcast.scala
index b72e8986d3..cf20f456c4 100644
--- a/core/src/main/scala/spark/broadcast/BitTorrentBroadcast.scala
+++ b/core/src/main/scala/spark/broadcast/BitTorrentBroadcast.scala
@@ -11,7 +11,7 @@ import scala.math
 import spark._
 import spark.storage.StorageLevel
 
-class BitTorrentBroadcast[T](@transient var value_ : T, isLocal: Boolean, id: Long)
+private[spark] class BitTorrentBroadcast[T](@transient var value_ : T, isLocal: Boolean, id: Long)
   extends Broadcast[T](id)
   with Logging
   with Serializable {
@@ -1027,7 +1027,7 @@ class BitTorrentBroadcast[T](@transient var value_ : T, isLocal: Boolean, id: Lo
   }
 }
 
-class BitTorrentBroadcastFactory
+private[spark] class BitTorrentBroadcastFactory
 extends BroadcastFactory {
   def initialize(isMaster: Boolean) { MultiTracker.initialize(isMaster) }
 
diff --git a/core/src/main/scala/spark/broadcast/Broadcast.scala b/core/src/main/scala/spark/broadcast/Broadcast.scala
index 3ba91c93e9..370978113f 100644
--- a/core/src/main/scala/spark/broadcast/Broadcast.scala
+++ b/core/src/main/scala/spark/broadcast/Broadcast.scala
@@ -5,7 +5,7 @@ import java.util.concurrent.atomic.AtomicLong
 
 import spark._
 
-abstract class Broadcast[T](id: Long) extends Serializable {
+private[spark] abstract class Broadcast[T](id: Long) extends Serializable {
   def value: T
 
   // We cannot have an abstract readObject here due to some weird issues with
@@ -14,7 +14,7 @@ abstract class Broadcast[T](id: Long) extends Serializable {
   override def toString = "spark.Broadcast(" + id + ")"
 }
 
-class BroadcastManager(val isMaster_ : Boolean) extends Logging with Serializable {
+private[spark] class BroadcastManager(val isMaster_ : Boolean) extends Logging with Serializable {
 
   private var initialized = false
   private var broadcastFactory: BroadcastFactory = null
diff --git a/core/src/main/scala/spark/broadcast/BroadcastFactory.scala b/core/src/main/scala/spark/broadcast/BroadcastFactory.scala
index 66ca8d56d5..ab6d302827 100644
--- a/core/src/main/scala/spark/broadcast/BroadcastFactory.scala
+++ b/core/src/main/scala/spark/broadcast/BroadcastFactory.scala
@@ -6,7 +6,7 @@ package spark.broadcast
  * BroadcastFactory implementation to instantiate a particular broadcast for the
  * entire Spark job.
  */
-trait BroadcastFactory {
+private[spark] trait BroadcastFactory {
   def initialize(isMaster: Boolean): Unit
   def newBroadcast[T](value_ : T, isLocal: Boolean, id: Long): Broadcast[T]
   def stop(): Unit
diff --git a/core/src/main/scala/spark/broadcast/HttpBroadcast.scala b/core/src/main/scala/spark/broadcast/HttpBroadcast.scala
index d8cf5e37d4..7eb4ddb74f 100644
--- a/core/src/main/scala/spark/broadcast/HttpBroadcast.scala
+++ b/core/src/main/scala/spark/broadcast/HttpBroadcast.scala
@@ -12,7 +12,7 @@ import it.unimi.dsi.fastutil.io.FastBufferedOutputStream
 import spark._
 import spark.storage.StorageLevel
 
-class HttpBroadcast[T](@transient var value_ : T, isLocal: Boolean, id: Long)
+private[spark] class HttpBroadcast[T](@transient var value_ : T, isLocal: Boolean, id: Long)
 extends Broadcast[T](id) with Logging with Serializable {
   
   def value = value_
@@ -46,7 +46,7 @@ extends Broadcast[T](id) with Logging with Serializable {
   }
 }
 
-class HttpBroadcastFactory extends BroadcastFactory {
+private[spark] class HttpBroadcastFactory extends BroadcastFactory {
   def initialize(isMaster: Boolean) { HttpBroadcast.initialize(isMaster) }
 
   def newBroadcast[T](value_ : T, isLocal: Boolean, id: Long) =
diff --git a/core/src/main/scala/spark/broadcast/MultiTracker.scala b/core/src/main/scala/spark/broadcast/MultiTracker.scala
index d00db23362..dd8e6dd246 100644
--- a/core/src/main/scala/spark/broadcast/MultiTracker.scala
+++ b/core/src/main/scala/spark/broadcast/MultiTracker.scala
@@ -382,10 +382,10 @@ extends Logging {
   }
 }
 
-case class BroadcastBlock(blockID: Int, byteArray: Array[Byte]) 
+private[spark] case class BroadcastBlock(blockID: Int, byteArray: Array[Byte]) 
 extends Serializable
 
-case class VariableInfo(@transient arrayOfBlocks : Array[BroadcastBlock],
+private[spark] case class VariableInfo(@transient arrayOfBlocks : Array[BroadcastBlock],
                         totalBlocks: Int, 
                         totalBytes: Int) 
 extends Serializable {
diff --git a/core/src/main/scala/spark/broadcast/SourceInfo.scala b/core/src/main/scala/spark/broadcast/SourceInfo.scala
index f90385fd47..705dd6fd81 100644
--- a/core/src/main/scala/spark/broadcast/SourceInfo.scala
+++ b/core/src/main/scala/spark/broadcast/SourceInfo.scala
@@ -7,7 +7,7 @@ import spark._
 /**
  * Used to keep and pass around information of peers involved in a broadcast
  */
-case class SourceInfo (hostAddress: String,
+private[spark] case class SourceInfo (hostAddress: String,
                        listenPort: Int,
                        totalBlocks: Int = SourceInfo.UnusedParam,
                        totalBytes: Int = SourceInfo.UnusedParam)
@@ -26,7 +26,7 @@ extends Comparable[SourceInfo] with Logging {
 /**
  * Helper Object of SourceInfo for its constants
  */
-object SourceInfo {
+private[spark] object SourceInfo {
   // Constants for special values of listenPort
   val TxNotStartedRetry = -1
   val TxOverGoToDefault = 0
diff --git a/core/src/main/scala/spark/broadcast/TreeBroadcast.scala b/core/src/main/scala/spark/broadcast/TreeBroadcast.scala
index c1148b22ca..5bd40a40e3 100644
--- a/core/src/main/scala/spark/broadcast/TreeBroadcast.scala
+++ b/core/src/main/scala/spark/broadcast/TreeBroadcast.scala
@@ -10,7 +10,7 @@ import scala.math
 import spark._
 import spark.storage.StorageLevel
 
-class TreeBroadcast[T](@transient var value_ : T, isLocal: Boolean, id: Long)
+private[spark] class TreeBroadcast[T](@transient var value_ : T, isLocal: Boolean, id: Long)
 extends Broadcast[T](id) with Logging with Serializable {
 
   def value = value_
@@ -572,7 +572,7 @@ extends Broadcast[T](id) with Logging with Serializable {
   }
 }
 
-class TreeBroadcastFactory
+private[spark] class TreeBroadcastFactory
 extends BroadcastFactory {
   def initialize(isMaster: Boolean) { MultiTracker.initialize(isMaster) }
 
diff --git a/core/src/main/scala/spark/deploy/Command.scala b/core/src/main/scala/spark/deploy/Command.scala
index 344888919a..577101e3c3 100644
--- a/core/src/main/scala/spark/deploy/Command.scala
+++ b/core/src/main/scala/spark/deploy/Command.scala
@@ -2,7 +2,7 @@ package spark.deploy
 
 import scala.collection.Map
 
-case class Command(
+private[spark] case class Command(
     mainClass: String,
     arguments: Seq[String],
     environment: Map[String, String]) {
diff --git a/core/src/main/scala/spark/deploy/DeployMessage.scala b/core/src/main/scala/spark/deploy/DeployMessage.scala
index 141bbe4d57..7eaae2c618 100644
--- a/core/src/main/scala/spark/deploy/DeployMessage.scala
+++ b/core/src/main/scala/spark/deploy/DeployMessage.scala
@@ -7,14 +7,14 @@ import scala.collection.immutable.List
 import scala.collection.mutable.HashMap
 
 
-sealed trait DeployMessage extends Serializable
+private[spark] sealed trait DeployMessage extends Serializable
 
 // Worker to Master
 
-case class RegisterWorker(id: String, host: String, port: Int, cores: Int, memory: Int, webUiPort: Int)
+private[spark] case class RegisterWorker(id: String, host: String, port: Int, cores: Int, memory: Int, webUiPort: Int)
   extends DeployMessage
 
-case class ExecutorStateChanged(
+private[spark] case class ExecutorStateChanged(
     jobId: String,
     execId: Int,
     state: ExecutorState,
@@ -23,11 +23,11 @@ case class ExecutorStateChanged(
 
 // Master to Worker
 
-case class RegisteredWorker(masterWebUiUrl: String) extends DeployMessage
-case class RegisterWorkerFailed(message: String) extends DeployMessage
-case class KillExecutor(jobId: String, execId: Int) extends DeployMessage
+private[spark] case class RegisteredWorker(masterWebUiUrl: String) extends DeployMessage
+private[spark] case class RegisterWorkerFailed(message: String) extends DeployMessage
+private[spark] case class KillExecutor(jobId: String, execId: Int) extends DeployMessage
 
-case class LaunchExecutor(
+private[spark] case class LaunchExecutor(
     jobId: String,
     execId: Int,
     jobDesc: JobDescription,
@@ -38,33 +38,33 @@ case class LaunchExecutor(
 
 // Client to Master
 
-case class RegisterJob(jobDescription: JobDescription) extends DeployMessage
+private[spark] case class RegisterJob(jobDescription: JobDescription) extends DeployMessage
 
 // Master to Client
 
-case class RegisteredJob(jobId: String) extends DeployMessage
-case class ExecutorAdded(id: Int, workerId: String, host: String, cores: Int, memory: Int)
-case class ExecutorUpdated(id: Int, state: ExecutorState, message: Option[String])
-case class JobKilled(message: String)
+private[spark] case class RegisteredJob(jobId: String) extends DeployMessage
+private[spark] case class ExecutorAdded(id: Int, workerId: String, host: String, cores: Int, memory: Int)
+private[spark] case class ExecutorUpdated(id: Int, state: ExecutorState, message: Option[String])
+private[spark] case class JobKilled(message: String)
 
 // Internal message in Client
 
-case object StopClient
+private[spark] case object StopClient
 
 // MasterWebUI To Master
 
-case object RequestMasterState
+private[spark] case object RequestMasterState
 
 // Master to MasterWebUI
 
-case class MasterState(uri : String, workers: List[WorkerInfo], activeJobs: List[JobInfo], 
+private[spark] case class MasterState(uri : String, workers: List[WorkerInfo], activeJobs: List[JobInfo], 
   completedJobs: List[JobInfo])
 
 //  WorkerWebUI to Worker
-case object RequestWorkerState
+private[spark] case object RequestWorkerState
 
 // Worker to WorkerWebUI
 
-case class WorkerState(uri: String, workerId: String, executors: List[ExecutorRunner], 
+private[spark] case class WorkerState(uri: String, workerId: String, executors: List[ExecutorRunner], 
   finishedExecutors: List[ExecutorRunner], masterUrl: String, cores: Int, memory: Int, 
   coresUsed: Int, memoryUsed: Int, masterWebUiUrl: String)
\ No newline at end of file
diff --git a/core/src/main/scala/spark/deploy/ExecutorState.scala b/core/src/main/scala/spark/deploy/ExecutorState.scala
index d6ff1c54ca..5dc0c54552 100644
--- a/core/src/main/scala/spark/deploy/ExecutorState.scala
+++ b/core/src/main/scala/spark/deploy/ExecutorState.scala
@@ -1,6 +1,6 @@
 package spark.deploy
 
-object ExecutorState
+private[spark] object ExecutorState
   extends Enumeration("LAUNCHING", "LOADING", "RUNNING", "KILLED", "FAILED", "LOST") {
 
   val LAUNCHING, LOADING, RUNNING, KILLED, FAILED, LOST = Value
diff --git a/core/src/main/scala/spark/deploy/JobDescription.scala b/core/src/main/scala/spark/deploy/JobDescription.scala
index 8ae77b1038..20879c5f11 100644
--- a/core/src/main/scala/spark/deploy/JobDescription.scala
+++ b/core/src/main/scala/spark/deploy/JobDescription.scala
@@ -1,6 +1,6 @@
 package spark.deploy
 
-class JobDescription(
+private[spark] class JobDescription(
     val name: String,
     val cores: Int,
     val memoryPerSlave: Int,
diff --git a/core/src/main/scala/spark/deploy/LocalSparkCluster.scala b/core/src/main/scala/spark/deploy/LocalSparkCluster.scala
index 1591bfdeb6..e938981f6e 100644
--- a/core/src/main/scala/spark/deploy/LocalSparkCluster.scala
+++ b/core/src/main/scala/spark/deploy/LocalSparkCluster.scala
@@ -9,7 +9,7 @@ import spark.{Logging, Utils}
 
 import scala.collection.mutable.ArrayBuffer
 
-class LocalSparkCluster(numSlaves: Int, coresPerSlave: Int, memoryPerSlave: Int) extends Logging {
+private[spark] class LocalSparkCluster(numSlaves: Int, coresPerSlave: Int, memoryPerSlave: Int) extends Logging {
   
   val localIpAddress = Utils.localIpAddress
   
diff --git a/core/src/main/scala/spark/deploy/client/Client.scala b/core/src/main/scala/spark/deploy/client/Client.scala
index a2f88fc5e5..b1b72a3a1f 100644
--- a/core/src/main/scala/spark/deploy/client/Client.scala
+++ b/core/src/main/scala/spark/deploy/client/Client.scala
@@ -16,7 +16,7 @@ import akka.dispatch.Await
  * The main class used to talk to a Spark deploy cluster. Takes a master URL, a job description,
  * and a listener for job events, and calls back the listener when various events occur.
  */
-class Client(
+private[spark] class Client(
     actorSystem: ActorSystem,
     masterUrl: String,
     jobDescription: JobDescription,
diff --git a/core/src/main/scala/spark/deploy/client/ClientListener.scala b/core/src/main/scala/spark/deploy/client/ClientListener.scala
index 7d23baff32..a8fa982085 100644
--- a/core/src/main/scala/spark/deploy/client/ClientListener.scala
+++ b/core/src/main/scala/spark/deploy/client/ClientListener.scala
@@ -7,7 +7,7 @@ package spark.deploy.client
  *
  * Users of this API should *not* block inside the callback methods.
  */
-trait ClientListener {
+private[spark] trait ClientListener {
   def connected(jobId: String): Unit
 
   def disconnected(): Unit
diff --git a/core/src/main/scala/spark/deploy/client/TestClient.scala b/core/src/main/scala/spark/deploy/client/TestClient.scala
index df9a36c7fe..bf0e7428ba 100644
--- a/core/src/main/scala/spark/deploy/client/TestClient.scala
+++ b/core/src/main/scala/spark/deploy/client/TestClient.scala
@@ -4,7 +4,7 @@ import spark.util.AkkaUtils
 import spark.{Logging, Utils}
 import spark.deploy.{Command, JobDescription}
 
-object TestClient {
+private[spark] object TestClient {
 
   class TestListener extends ClientListener with Logging {
     def connected(id: String) {
diff --git a/core/src/main/scala/spark/deploy/client/TestExecutor.scala b/core/src/main/scala/spark/deploy/client/TestExecutor.scala
index 2e40e10d18..0e46db2272 100644
--- a/core/src/main/scala/spark/deploy/client/TestExecutor.scala
+++ b/core/src/main/scala/spark/deploy/client/TestExecutor.scala
@@ -1,6 +1,6 @@
 package spark.deploy.client
 
-object TestExecutor {
+private[spark] object TestExecutor {
   def main(args: Array[String]) {
     println("Hello world!")
     while (true) {
diff --git a/core/src/main/scala/spark/deploy/master/ExecutorInfo.scala b/core/src/main/scala/spark/deploy/master/ExecutorInfo.scala
index 335e00958c..1db2c32633 100644
--- a/core/src/main/scala/spark/deploy/master/ExecutorInfo.scala
+++ b/core/src/main/scala/spark/deploy/master/ExecutorInfo.scala
@@ -2,7 +2,7 @@ package spark.deploy.master
 
 import spark.deploy.ExecutorState
 
-class ExecutorInfo(
+private[spark] class ExecutorInfo(
     val id: Int,
     val job: JobInfo,
     val worker: WorkerInfo,
diff --git a/core/src/main/scala/spark/deploy/master/JobInfo.scala b/core/src/main/scala/spark/deploy/master/JobInfo.scala
index 4c81a1b447..e2364f1863 100644
--- a/core/src/main/scala/spark/deploy/master/JobInfo.scala
+++ b/core/src/main/scala/spark/deploy/master/JobInfo.scala
@@ -5,7 +5,7 @@ import java.util.Date
 import akka.actor.ActorRef
 import scala.collection.mutable
 
-class JobInfo(val id: String, val desc: JobDescription, val submitDate: Date, val actor: ActorRef) {
+private[spark] class JobInfo(val id: String, val desc: JobDescription, val submitDate: Date, val actor: ActorRef) {
   var state = JobState.WAITING
   var executors = new mutable.HashMap[Int, ExecutorInfo]
   var coresGranted = 0
diff --git a/core/src/main/scala/spark/deploy/master/JobState.scala b/core/src/main/scala/spark/deploy/master/JobState.scala
index 8d458ac39c..2b70cf0191 100644
--- a/core/src/main/scala/spark/deploy/master/JobState.scala
+++ b/core/src/main/scala/spark/deploy/master/JobState.scala
@@ -1,6 +1,6 @@
 package spark.deploy.master
 
-object JobState extends Enumeration("WAITING", "RUNNING", "FINISHED", "FAILED") {
+private[spark] object JobState extends Enumeration("WAITING", "RUNNING", "FINISHED", "FAILED") {
   type JobState = Value
 
   val WAITING, RUNNING, FINISHED, FAILED = Value
diff --git a/core/src/main/scala/spark/deploy/master/Master.scala b/core/src/main/scala/spark/deploy/master/Master.scala
index 5cc73633ab..6010f7cff2 100644
--- a/core/src/main/scala/spark/deploy/master/Master.scala
+++ b/core/src/main/scala/spark/deploy/master/Master.scala
@@ -14,7 +14,7 @@ import spark.{Logging, SparkException, Utils}
 import spark.util.AkkaUtils
 
 
-class Master(ip: String, port: Int, webUiPort: Int) extends Actor with Logging {
+private[spark] class Master(ip: String, port: Int, webUiPort: Int) extends Actor with Logging {
   val DATE_FORMAT = new SimpleDateFormat("yyyyMMddHHmmss")  // For job IDs
 
   var nextJobNumber = 0
@@ -212,7 +212,7 @@ class Master(ip: String, port: Int, webUiPort: Int) extends Actor with Logging {
   }
 }
 
-object Master {
+private[spark] object Master {
   def main(argStrings: Array[String]) {
     val args = new MasterArguments(argStrings)
     val (actorSystem, boundPort) = AkkaUtils.createActorSystem("spark", args.ip, args.port)
diff --git a/core/src/main/scala/spark/deploy/master/MasterArguments.scala b/core/src/main/scala/spark/deploy/master/MasterArguments.scala
index d712e3d5b3..1b1c3dd0ad 100644
--- a/core/src/main/scala/spark/deploy/master/MasterArguments.scala
+++ b/core/src/main/scala/spark/deploy/master/MasterArguments.scala
@@ -6,7 +6,7 @@ import spark.Utils
 /**
  * Command-line parser for the master.
  */
-class MasterArguments(args: Array[String]) {
+private[spark] class MasterArguments(args: Array[String]) {
   var ip = Utils.localIpAddress()
   var port = 7077
   var webUiPort = 8080
diff --git a/core/src/main/scala/spark/deploy/master/MasterWebUI.scala b/core/src/main/scala/spark/deploy/master/MasterWebUI.scala
index 9f9994e4ba..c083e7f5ea 100644
--- a/core/src/main/scala/spark/deploy/master/MasterWebUI.scala
+++ b/core/src/main/scala/spark/deploy/master/MasterWebUI.scala
@@ -10,7 +10,7 @@ import cc.spray.directives._
 import cc.spray.typeconversion.TwirlSupport._
 import spark.deploy._
 
-class MasterWebUI(val actorSystem: ActorSystem, master: ActorRef) extends Directives {
+private[spark] class MasterWebUI(val actorSystem: ActorSystem, master: ActorRef) extends Directives {
   val RESOURCE_DIR = "spark/deploy/master/webui"
   val STATIC_RESOURCE_DIR = "spark/deploy/static"
   
diff --git a/core/src/main/scala/spark/deploy/master/WorkerInfo.scala b/core/src/main/scala/spark/deploy/master/WorkerInfo.scala
index 59474a0945..16b3f9b653 100644
--- a/core/src/main/scala/spark/deploy/master/WorkerInfo.scala
+++ b/core/src/main/scala/spark/deploy/master/WorkerInfo.scala
@@ -3,7 +3,7 @@ package spark.deploy.master
 import akka.actor.ActorRef
 import scala.collection.mutable
 
-class WorkerInfo(
+private[spark] class WorkerInfo(
   val id: String,
   val host: String,
   val port: Int,
diff --git a/core/src/main/scala/spark/deploy/worker/ExecutorRunner.scala b/core/src/main/scala/spark/deploy/worker/ExecutorRunner.scala
index e2a9df275a..73722a82e0 100644
--- a/core/src/main/scala/spark/deploy/worker/ExecutorRunner.scala
+++ b/core/src/main/scala/spark/deploy/worker/ExecutorRunner.scala
@@ -13,7 +13,7 @@ import spark.deploy.ExecutorStateChanged
 /**
  * Manages the execution of one executor process.
  */
-class ExecutorRunner(
+private[spark] class ExecutorRunner(
     val jobId: String,
     val execId: Int,
     val jobDesc: JobDescription,
diff --git a/core/src/main/scala/spark/deploy/worker/Worker.scala b/core/src/main/scala/spark/deploy/worker/Worker.scala
index 645613257d..474c9364fd 100644
--- a/core/src/main/scala/spark/deploy/worker/Worker.scala
+++ b/core/src/main/scala/spark/deploy/worker/Worker.scala
@@ -16,7 +16,7 @@ import spark.deploy.RegisterWorkerFailed
 import akka.actor.Terminated
 import java.io.File
 
-class Worker(
+private[spark] class Worker(
     ip: String,
     port: Int,
     webUiPort: Int,
@@ -170,7 +170,7 @@ class Worker(
   }
 }
 
-object Worker {
+private[spark] object Worker {
   def main(argStrings: Array[String]) {
     val args = new WorkerArguments(argStrings)
     val (actorSystem, boundPort) = AkkaUtils.createActorSystem("spark", args.ip, args.port)
diff --git a/core/src/main/scala/spark/deploy/worker/WorkerArguments.scala b/core/src/main/scala/spark/deploy/worker/WorkerArguments.scala
index 059c40da9f..60dc107a4c 100644
--- a/core/src/main/scala/spark/deploy/worker/WorkerArguments.scala
+++ b/core/src/main/scala/spark/deploy/worker/WorkerArguments.scala
@@ -8,7 +8,7 @@ import java.lang.management.ManagementFactory
 /**
  * Command-line parser for the master.
  */
-class WorkerArguments(args: Array[String]) {
+private[spark] class WorkerArguments(args: Array[String]) {
   var ip = Utils.localIpAddress()
   var port = 0
   var webUiPort = 8081
diff --git a/core/src/main/scala/spark/deploy/worker/WorkerWebUI.scala b/core/src/main/scala/spark/deploy/worker/WorkerWebUI.scala
index f84b92b63e..78a9adc86f 100644
--- a/core/src/main/scala/spark/deploy/worker/WorkerWebUI.scala
+++ b/core/src/main/scala/spark/deploy/worker/WorkerWebUI.scala
@@ -9,7 +9,7 @@ import cc.spray.Directives
 import cc.spray.typeconversion.TwirlSupport._
 import spark.deploy.{WorkerState, RequestWorkerState}
 
-class WorkerWebUI(val actorSystem: ActorSystem, worker: ActorRef) extends Directives {
+private[spark] class WorkerWebUI(val actorSystem: ActorSystem, worker: ActorRef) extends Directives {
   val RESOURCE_DIR = "spark/deploy/worker/webui"
   val STATIC_RESOURCE_DIR = "spark/deploy/static"
   
diff --git a/core/src/main/scala/spark/executor/Executor.scala b/core/src/main/scala/spark/executor/Executor.scala
index 820428c727..6ecf9fa8da 100644
--- a/core/src/main/scala/spark/executor/Executor.scala
+++ b/core/src/main/scala/spark/executor/Executor.scala
@@ -16,7 +16,7 @@ import java.nio.ByteBuffer
 /**
  * The Mesos executor for Spark.
  */
-class Executor extends Logging {
+private[spark] class Executor extends Logging {
   var urlClassLoader : ExecutorURLClassLoader = null
   var threadPool: ExecutorService = null
   var env: SparkEnv = null
diff --git a/core/src/main/scala/spark/executor/ExecutorBackend.scala b/core/src/main/scala/spark/executor/ExecutorBackend.scala
index 24c8776f31..e97e509700 100644
--- a/core/src/main/scala/spark/executor/ExecutorBackend.scala
+++ b/core/src/main/scala/spark/executor/ExecutorBackend.scala
@@ -6,6 +6,6 @@ import spark.TaskState.TaskState
 /**
  * A pluggable interface used by the Executor to send updates to the cluster scheduler.
  */
-trait ExecutorBackend {
+private[spark] trait ExecutorBackend {
   def statusUpdate(taskId: Long, state: TaskState, data: ByteBuffer)
 }
diff --git a/core/src/main/scala/spark/executor/ExecutorURLClassLoader.scala b/core/src/main/scala/spark/executor/ExecutorURLClassLoader.scala
index f74f036c4c..5beb4d049e 100644
--- a/core/src/main/scala/spark/executor/ExecutorURLClassLoader.scala
+++ b/core/src/main/scala/spark/executor/ExecutorURLClassLoader.scala
@@ -5,8 +5,7 @@ import java.net.{URLClassLoader, URL}
 /**
  * The addURL method in URLClassLoader is protected. We subclass it to make this accessible.
  */
-private[spark]
-class ExecutorURLClassLoader(urls: Array[URL], parent: ClassLoader)
+private[spark] class ExecutorURLClassLoader(urls: Array[URL], parent: ClassLoader)
   extends URLClassLoader(urls, parent) {
 
   override def addURL(url: URL) {
diff --git a/core/src/main/scala/spark/executor/MesosExecutorBackend.scala b/core/src/main/scala/spark/executor/MesosExecutorBackend.scala
index 50f4e41ede..eeab3959c6 100644
--- a/core/src/main/scala/spark/executor/MesosExecutorBackend.scala
+++ b/core/src/main/scala/spark/executor/MesosExecutorBackend.scala
@@ -8,7 +8,7 @@ import com.google.protobuf.ByteString
 import spark.{Utils, Logging}
 import spark.TaskState
 
-class MesosExecutorBackend(executor: Executor)
+private[spark] class MesosExecutorBackend(executor: Executor)
   extends MesosExecutor
   with ExecutorBackend
   with Logging {
@@ -59,7 +59,7 @@ class MesosExecutorBackend(executor: Executor)
 /**
  * Entry point for Mesos executor.
  */
-object MesosExecutorBackend {
+private[spark] object MesosExecutorBackend {
   def main(args: Array[String]) {
     MesosNativeLibrary.load()
     // Create a new Executor and start it running
diff --git a/core/src/main/scala/spark/executor/StandaloneExecutorBackend.scala b/core/src/main/scala/spark/executor/StandaloneExecutorBackend.scala
index 26b163de0a..915f71ba9f 100644
--- a/core/src/main/scala/spark/executor/StandaloneExecutorBackend.scala
+++ b/core/src/main/scala/spark/executor/StandaloneExecutorBackend.scala
@@ -14,7 +14,7 @@ import spark.scheduler.cluster.RegisterSlaveFailed
 import spark.scheduler.cluster.RegisterSlave
 
 
-class StandaloneExecutorBackend(
+private[spark] class StandaloneExecutorBackend(
     executor: Executor,
     masterUrl: String,
     slaveId: String,
@@ -62,7 +62,7 @@ class StandaloneExecutorBackend(
   }
 }
 
-object StandaloneExecutorBackend {
+private[spark] object StandaloneExecutorBackend {
   def run(masterUrl: String, slaveId: String, hostname: String, cores: Int) {
     // Create a new ActorSystem to run the backend, because we can't create a SparkEnv / Executor
     // before getting started with all our system properties, etc
diff --git a/core/src/main/scala/spark/network/Connection.scala b/core/src/main/scala/spark/network/Connection.scala
index c4350173fc..3a03f6843a 100644
--- a/core/src/main/scala/spark/network/Connection.scala
+++ b/core/src/main/scala/spark/network/Connection.scala
@@ -11,7 +11,7 @@ import java.nio.channels.spi._
 import java.net._
 
 
-abstract class Connection(val channel: SocketChannel, val selector: Selector) extends Logging {
+private[spark] abstract class Connection(val channel: SocketChannel, val selector: Selector) extends Logging {
 
   channel.configureBlocking(false)
   channel.socket.setTcpNoDelay(true)
@@ -102,7 +102,7 @@ abstract class Connection(val channel: SocketChannel, val selector: Selector) ex
 }
 
 
-class SendingConnection(val address: InetSocketAddress, selector_ : Selector) 
+private[spark] class SendingConnection(val address: InetSocketAddress, selector_ : Selector) 
 extends Connection(SocketChannel.open, selector_) {
 
   class Outbox(fair: Int = 0) {
@@ -259,7 +259,7 @@ extends Connection(SocketChannel.open, selector_) {
 }
 
 
-class ReceivingConnection(channel_ : SocketChannel, selector_ : Selector) 
+private[spark] class ReceivingConnection(channel_ : SocketChannel, selector_ : Selector) 
 extends Connection(channel_, selector_) {
   
   class Inbox() {
diff --git a/core/src/main/scala/spark/network/ConnectionManager.scala b/core/src/main/scala/spark/network/ConnectionManager.scala
index 2bb5f5fc6b..dec0df25b4 100644
--- a/core/src/main/scala/spark/network/ConnectionManager.scala
+++ b/core/src/main/scala/spark/network/ConnectionManager.scala
@@ -18,17 +18,17 @@ import akka.dispatch.{Await, Promise, ExecutionContext, Future}
 import akka.util.Duration
 import akka.util.duration._
 
-case class ConnectionManagerId(host: String, port: Int) {
+private[spark] case class ConnectionManagerId(host: String, port: Int) {
   def toSocketAddress() = new InetSocketAddress(host, port)
 }
 
-object ConnectionManagerId {
+private[spark] object ConnectionManagerId {
   def fromSocketAddress(socketAddress: InetSocketAddress): ConnectionManagerId = {
     new ConnectionManagerId(socketAddress.getHostName(), socketAddress.getPort())
   }
 }
   
-class ConnectionManager(port: Int) extends Logging {
+private[spark] class ConnectionManager(port: Int) extends Logging {
 
   class MessageStatus(
       val message: Message,
@@ -349,7 +349,7 @@ class ConnectionManager(port: Int) extends Logging {
 }
 
 
-object ConnectionManager {
+private[spark] object ConnectionManager {
 
   def main(args: Array[String]) {
   
diff --git a/core/src/main/scala/spark/network/ConnectionManagerTest.scala b/core/src/main/scala/spark/network/ConnectionManagerTest.scala
index 555b3454ee..47ceaf3c07 100644
--- a/core/src/main/scala/spark/network/ConnectionManagerTest.scala
+++ b/core/src/main/scala/spark/network/ConnectionManagerTest.scala
@@ -11,7 +11,7 @@ import java.net.InetAddress
 import akka.dispatch.Await
 import akka.util.duration._
 
-object ConnectionManagerTest extends Logging{
+private[spark] object ConnectionManagerTest extends Logging{
   def main(args: Array[String]) {
     if (args.length < 2) {
       println("Usage: ConnectionManagerTest <mesos cluster> <slaves file>")
diff --git a/core/src/main/scala/spark/network/Message.scala b/core/src/main/scala/spark/network/Message.scala
index 62a06d95c5..525751b5bf 100644
--- a/core/src/main/scala/spark/network/Message.scala
+++ b/core/src/main/scala/spark/network/Message.scala
@@ -9,7 +9,7 @@ import java.net.InetAddress
 import java.net.InetSocketAddress
 import storage.BlockManager
 
-class MessageChunkHeader(
+private[spark] class MessageChunkHeader(
     val typ: Long,
     val id: Int,
     val totalSize: Int,
@@ -37,7 +37,7 @@ class MessageChunkHeader(
       " and sizes " + totalSize + " / " + chunkSize + " bytes"
 }
 
-class MessageChunk(val header: MessageChunkHeader, val buffer: ByteBuffer) {
+private[spark] class MessageChunk(val header: MessageChunkHeader, val buffer: ByteBuffer) {
   val size = if (buffer == null) 0 else buffer.remaining
   lazy val buffers = {
     val ab = new ArrayBuffer[ByteBuffer]()
@@ -51,7 +51,7 @@ class MessageChunk(val header: MessageChunkHeader, val buffer: ByteBuffer) {
   override def toString = "" + this.getClass.getSimpleName + " (id = " + header.id + ", size = " + size + ")"
 }
 
-abstract class Message(val typ: Long, val id: Int) {
+private[spark] abstract class Message(val typ: Long, val id: Int) {
   var senderAddress: InetSocketAddress = null
   var started = false
   var startTime = -1L
@@ -68,7 +68,7 @@ abstract class Message(val typ: Long, val id: Int) {
   override def toString = this.getClass.getSimpleName + "(id = " + id + ", size = " + size + ")"
 }
 
-class BufferMessage(id_ : Int, val buffers: ArrayBuffer[ByteBuffer], var ackId: Int) 
+private[spark] class BufferMessage(id_ : Int, val buffers: ArrayBuffer[ByteBuffer], var ackId: Int) 
 extends Message(Message.BUFFER_MESSAGE, id_) {
   
   val initialSize = currentSize() 
@@ -152,7 +152,7 @@ extends Message(Message.BUFFER_MESSAGE, id_) {
   }
 }
 
-object MessageChunkHeader {
+private[spark] object MessageChunkHeader {
   val HEADER_SIZE = 40 
   
   def create(buffer: ByteBuffer): MessageChunkHeader = {
@@ -173,7 +173,7 @@ object MessageChunkHeader {
   }
 }
 
-object Message {
+private[spark] object Message {
   val BUFFER_MESSAGE = 1111111111L
 
   var lastId = 1
diff --git a/core/src/main/scala/spark/network/ReceiverTest.scala b/core/src/main/scala/spark/network/ReceiverTest.scala
index e1ba7c06c0..a174d5f403 100644
--- a/core/src/main/scala/spark/network/ReceiverTest.scala
+++ b/core/src/main/scala/spark/network/ReceiverTest.scala
@@ -3,7 +3,7 @@ package spark.network
 import java.nio.ByteBuffer
 import java.net.InetAddress
 
-object ReceiverTest {
+private[spark] object ReceiverTest {
 
   def main(args: Array[String]) {
     val manager = new ConnectionManager(9999)
diff --git a/core/src/main/scala/spark/network/SenderTest.scala b/core/src/main/scala/spark/network/SenderTest.scala
index 4ab6dd3414..a4ff69e4d2 100644
--- a/core/src/main/scala/spark/network/SenderTest.scala
+++ b/core/src/main/scala/spark/network/SenderTest.scala
@@ -3,7 +3,7 @@ package spark.network
 import java.nio.ByteBuffer
 import java.net.InetAddress
 
-object SenderTest {
+private[spark] object SenderTest {
 
   def main(args: Array[String]) {
     
diff --git a/core/src/main/scala/spark/partial/ApproximateActionListener.scala b/core/src/main/scala/spark/partial/ApproximateActionListener.scala
index e6535836ab..42f46e06ed 100644
--- a/core/src/main/scala/spark/partial/ApproximateActionListener.scala
+++ b/core/src/main/scala/spark/partial/ApproximateActionListener.scala
@@ -12,7 +12,7 @@ import spark.scheduler.JobListener
  * a result of type U for each partition, and that the action returns a partial or complete result
  * of type R. Note that the type R must *include* any error bars on it (e.g. see BoundedInt).
  */
-class ApproximateActionListener[T, U, R](
+private[spark] class ApproximateActionListener[T, U, R](
     rdd: RDD[T],
     func: (TaskContext, Iterator[T]) => U,
     evaluator: ApproximateEvaluator[U, R],
diff --git a/core/src/main/scala/spark/partial/ApproximateEvaluator.scala b/core/src/main/scala/spark/partial/ApproximateEvaluator.scala
index 4772e43ef0..75713b2eaa 100644
--- a/core/src/main/scala/spark/partial/ApproximateEvaluator.scala
+++ b/core/src/main/scala/spark/partial/ApproximateEvaluator.scala
@@ -4,7 +4,7 @@ package spark.partial
  * An object that computes a function incrementally by merging in results of type U from multiple
  * tasks. Allows partial evaluation at any point by calling currentResult().
  */
-trait ApproximateEvaluator[U, R] {
+private[spark] trait ApproximateEvaluator[U, R] {
   def merge(outputId: Int, taskResult: U): Unit
   def currentResult(): R
 }
diff --git a/core/src/main/scala/spark/partial/BoundedDouble.scala b/core/src/main/scala/spark/partial/BoundedDouble.scala
index 463c33d6e2..ab5cc21aa0 100644
--- a/core/src/main/scala/spark/partial/BoundedDouble.scala
+++ b/core/src/main/scala/spark/partial/BoundedDouble.scala
@@ -3,6 +3,6 @@ package spark.partial
 /**
  * A Double with error bars on it.
  */
-class BoundedDouble(val mean: Double, val confidence: Double, val low: Double, val high: Double) {
+private[spark] class BoundedDouble(val mean: Double, val confidence: Double, val low: Double, val high: Double) {
   override def toString(): String = "[%.3f, %.3f]".format(low, high)
 }
diff --git a/core/src/main/scala/spark/partial/CountEvaluator.scala b/core/src/main/scala/spark/partial/CountEvaluator.scala
index 1bc90d6b39..daf2c5170c 100644
--- a/core/src/main/scala/spark/partial/CountEvaluator.scala
+++ b/core/src/main/scala/spark/partial/CountEvaluator.scala
@@ -8,7 +8,7 @@ import cern.jet.stat.Probability
  * TODO: There's currently a lot of shared code between this and GroupedCountEvaluator. It might
  * be best to make this a special case of GroupedCountEvaluator with one group.
  */
-class CountEvaluator(totalOutputs: Int, confidence: Double)
+private[spark] class CountEvaluator(totalOutputs: Int, confidence: Double)
   extends ApproximateEvaluator[Long, BoundedDouble] {
 
   var outputsMerged = 0
diff --git a/core/src/main/scala/spark/partial/GroupedCountEvaluator.scala b/core/src/main/scala/spark/partial/GroupedCountEvaluator.scala
index 3e631c0efc..01fbb8a11b 100644
--- a/core/src/main/scala/spark/partial/GroupedCountEvaluator.scala
+++ b/core/src/main/scala/spark/partial/GroupedCountEvaluator.scala
@@ -14,7 +14,7 @@ import it.unimi.dsi.fastutil.objects.{Object2LongOpenHashMap => OLMap}
 /**
  * An ApproximateEvaluator for counts by key. Returns a map of key to confidence interval.
  */
-class GroupedCountEvaluator[T](totalOutputs: Int, confidence: Double)
+private[spark] class GroupedCountEvaluator[T](totalOutputs: Int, confidence: Double)
   extends ApproximateEvaluator[OLMap[T], Map[T, BoundedDouble]] {
 
   var outputsMerged = 0
diff --git a/core/src/main/scala/spark/partial/GroupedMeanEvaluator.scala b/core/src/main/scala/spark/partial/GroupedMeanEvaluator.scala
index 2a9ccba205..c622df5220 100644
--- a/core/src/main/scala/spark/partial/GroupedMeanEvaluator.scala
+++ b/core/src/main/scala/spark/partial/GroupedMeanEvaluator.scala
@@ -12,7 +12,7 @@ import spark.util.StatCounter
 /**
  * An ApproximateEvaluator for means by key. Returns a map of key to confidence interval.
  */
-class GroupedMeanEvaluator[T](totalOutputs: Int, confidence: Double)
+private[spark] class GroupedMeanEvaluator[T](totalOutputs: Int, confidence: Double)
   extends ApproximateEvaluator[JHashMap[T, StatCounter], Map[T, BoundedDouble]] {
 
   var outputsMerged = 0
diff --git a/core/src/main/scala/spark/partial/GroupedSumEvaluator.scala b/core/src/main/scala/spark/partial/GroupedSumEvaluator.scala
index 6a2ec7a7bd..20fa55cff2 100644
--- a/core/src/main/scala/spark/partial/GroupedSumEvaluator.scala
+++ b/core/src/main/scala/spark/partial/GroupedSumEvaluator.scala
@@ -12,7 +12,7 @@ import spark.util.StatCounter
 /**
  * An ApproximateEvaluator for sums by key. Returns a map of key to confidence interval.
  */
-class GroupedSumEvaluator[T](totalOutputs: Int, confidence: Double)
+private[spark] class GroupedSumEvaluator[T](totalOutputs: Int, confidence: Double)
   extends ApproximateEvaluator[JHashMap[T, StatCounter], Map[T, BoundedDouble]] {
 
   var outputsMerged = 0
diff --git a/core/src/main/scala/spark/partial/MeanEvaluator.scala b/core/src/main/scala/spark/partial/MeanEvaluator.scala
index b8c7cb8863..762c85400d 100644
--- a/core/src/main/scala/spark/partial/MeanEvaluator.scala
+++ b/core/src/main/scala/spark/partial/MeanEvaluator.scala
@@ -7,7 +7,7 @@ import spark.util.StatCounter
 /**
  * An ApproximateEvaluator for means.
  */
-class MeanEvaluator(totalOutputs: Int, confidence: Double)
+private[spark] class MeanEvaluator(totalOutputs: Int, confidence: Double)
   extends ApproximateEvaluator[StatCounter, BoundedDouble] {
 
   var outputsMerged = 0
diff --git a/core/src/main/scala/spark/partial/PartialResult.scala b/core/src/main/scala/spark/partial/PartialResult.scala
index 200ed4ea1e..beafbf67c3 100644
--- a/core/src/main/scala/spark/partial/PartialResult.scala
+++ b/core/src/main/scala/spark/partial/PartialResult.scala
@@ -1,6 +1,6 @@
 package spark.partial
 
-class PartialResult[R](initialVal: R, isFinal: Boolean) {
+private[spark] class PartialResult[R](initialVal: R, isFinal: Boolean) {
   private var finalValue: Option[R] = if (isFinal) Some(initialVal) else None
   private var failure: Option[Exception] = None
   private var completionHandler: Option[R => Unit] = None
diff --git a/core/src/main/scala/spark/partial/StudentTCacher.scala b/core/src/main/scala/spark/partial/StudentTCacher.scala
index 6263ee3518..443abba5cd 100644
--- a/core/src/main/scala/spark/partial/StudentTCacher.scala
+++ b/core/src/main/scala/spark/partial/StudentTCacher.scala
@@ -7,7 +7,7 @@ import cern.jet.stat.Probability
  * and various sample sizes. This is used by the MeanEvaluator to efficiently calculate
  * confidence intervals for many keys.
  */
-class StudentTCacher(confidence: Double) {
+private[spark] class StudentTCacher(confidence: Double) {
   val NORMAL_APPROX_SAMPLE_SIZE = 100  // For samples bigger than this, use Gaussian approximation
   val normalApprox = Probability.normalInverse(1 - (1 - confidence) / 2)
   val cache = Array.fill[Double](NORMAL_APPROX_SAMPLE_SIZE)(-1.0)
diff --git a/core/src/main/scala/spark/partial/SumEvaluator.scala b/core/src/main/scala/spark/partial/SumEvaluator.scala
index 0357a6bff8..58fb60f441 100644
--- a/core/src/main/scala/spark/partial/SumEvaluator.scala
+++ b/core/src/main/scala/spark/partial/SumEvaluator.scala
@@ -9,7 +9,7 @@ import spark.util.StatCounter
  * together, then uses the formula for the variance of two independent random variables to get
  * a variance for the result and compute a confidence interval.
  */
-class SumEvaluator(totalOutputs: Int, confidence: Double)
+private[spark] class SumEvaluator(totalOutputs: Int, confidence: Double)
   extends ApproximateEvaluator[StatCounter, BoundedDouble] {
 
   var outputsMerged = 0
diff --git a/core/src/main/scala/spark/scheduler/ActiveJob.scala b/core/src/main/scala/spark/scheduler/ActiveJob.scala
index e09b92d667..5a4e9a582d 100644
--- a/core/src/main/scala/spark/scheduler/ActiveJob.scala
+++ b/core/src/main/scala/spark/scheduler/ActiveJob.scala
@@ -5,7 +5,7 @@ import spark.TaskContext
 /**
  * Tracks information about an active job in the DAGScheduler.
  */
-class ActiveJob(
+private[spark] class ActiveJob(
     val runId: Int,
     val finalStage: Stage,
     val func: (TaskContext, Iterator[_]) => _,
diff --git a/core/src/main/scala/spark/scheduler/DAGScheduler.scala b/core/src/main/scala/spark/scheduler/DAGScheduler.scala
index 70931407ce..33388545c4 100644
--- a/core/src/main/scala/spark/scheduler/DAGScheduler.scala
+++ b/core/src/main/scala/spark/scheduler/DAGScheduler.scala
@@ -21,7 +21,7 @@ import spark.storage.BlockManagerId
  * schedule to run the job. Subclasses only need to implement the code to send a task to the cluster
  * and to report fetch failures (the submitTasks method, and code to add CompletionEvents).
  */
-class DAGScheduler(taskSched: TaskScheduler) extends TaskSchedulerListener with Logging {
+private[spark] class DAGScheduler(taskSched: TaskScheduler) extends TaskSchedulerListener with Logging {
   taskSched.setListener(this)
 
   // Called by TaskScheduler to report task completions or failures.
diff --git a/core/src/main/scala/spark/scheduler/DAGSchedulerEvent.scala b/core/src/main/scala/spark/scheduler/DAGSchedulerEvent.scala
index 11f0ef6245..3422a21d9d 100644
--- a/core/src/main/scala/spark/scheduler/DAGSchedulerEvent.scala
+++ b/core/src/main/scala/spark/scheduler/DAGSchedulerEvent.scala
@@ -10,9 +10,9 @@ import spark._
  * submitted) but there is a single "logic" thread that reads these events and takes decisions.
  * This greatly simplifies synchronization.
  */
-sealed trait DAGSchedulerEvent
+private[spark] sealed trait DAGSchedulerEvent
 
-case class JobSubmitted(
+private[spark] case class JobSubmitted(
     finalRDD: RDD[_],
     func: (TaskContext, Iterator[_]) => _,
     partitions: Array[Int],
@@ -21,15 +21,15 @@ case class JobSubmitted(
     listener: JobListener)
   extends DAGSchedulerEvent
 
-case class CompletionEvent(
+private[spark] case class CompletionEvent(
     task: Task[_],
     reason: TaskEndReason,
     result: Any,
     accumUpdates: Map[Long, Any])
   extends DAGSchedulerEvent
 
-case class HostLost(host: String) extends DAGSchedulerEvent
+private[spark] case class HostLost(host: String) extends DAGSchedulerEvent
 
-case class TaskSetFailed(taskSet: TaskSet, reason: String) extends DAGSchedulerEvent
+private[spark] case class TaskSetFailed(taskSet: TaskSet, reason: String) extends DAGSchedulerEvent
 
-case object StopDAGScheduler extends DAGSchedulerEvent
+private[spark] case object StopDAGScheduler extends DAGSchedulerEvent
diff --git a/core/src/main/scala/spark/scheduler/JobListener.scala b/core/src/main/scala/spark/scheduler/JobListener.scala
index d4dd536a7d..f46b9d551d 100644
--- a/core/src/main/scala/spark/scheduler/JobListener.scala
+++ b/core/src/main/scala/spark/scheduler/JobListener.scala
@@ -5,7 +5,7 @@ package spark.scheduler
  * DAGScheduler. The listener is notified each time a task succeeds, as well as if the whole
  * job fails (and no further taskSucceeded events will happen).
  */
-trait JobListener {
+private[spark] trait JobListener {
   def taskSucceeded(index: Int, result: Any)
   def jobFailed(exception: Exception)
 }
diff --git a/core/src/main/scala/spark/scheduler/JobResult.scala b/core/src/main/scala/spark/scheduler/JobResult.scala
index 62b458eccb..c4a74e526f 100644
--- a/core/src/main/scala/spark/scheduler/JobResult.scala
+++ b/core/src/main/scala/spark/scheduler/JobResult.scala
@@ -3,7 +3,7 @@ package spark.scheduler
 /**
  * A result of a job in the DAGScheduler.
  */
-sealed trait JobResult
+private[spark] sealed trait JobResult
 
-case class JobSucceeded(results: Seq[_]) extends JobResult
-case class JobFailed(exception: Exception) extends JobResult
+private[spark] case class JobSucceeded(results: Seq[_]) extends JobResult
+private[spark] case class JobFailed(exception: Exception) extends JobResult
diff --git a/core/src/main/scala/spark/scheduler/JobWaiter.scala b/core/src/main/scala/spark/scheduler/JobWaiter.scala
index 4c2ae23051..b3d4feebe5 100644
--- a/core/src/main/scala/spark/scheduler/JobWaiter.scala
+++ b/core/src/main/scala/spark/scheduler/JobWaiter.scala
@@ -5,7 +5,7 @@ import scala.collection.mutable.ArrayBuffer
 /**
  * An object that waits for a DAGScheduler job to complete.
  */
-class JobWaiter(totalTasks: Int) extends JobListener {
+private[spark] class JobWaiter(totalTasks: Int) extends JobListener {
   private val taskResults = ArrayBuffer.fill[Any](totalTasks)(null)
   private var finishedTasks = 0
 
diff --git a/core/src/main/scala/spark/scheduler/ResultTask.scala b/core/src/main/scala/spark/scheduler/ResultTask.scala
index 090ced9d76..2ebd4075a2 100644
--- a/core/src/main/scala/spark/scheduler/ResultTask.scala
+++ b/core/src/main/scala/spark/scheduler/ResultTask.scala
@@ -2,7 +2,7 @@ package spark.scheduler
 
 import spark._
 
-class ResultTask[T, U](
+private[spark] class ResultTask[T, U](
     stageId: Int,
     rdd: RDD[T],
     func: (TaskContext, Iterator[T]) => U,
diff --git a/core/src/main/scala/spark/scheduler/ShuffleMapTask.scala b/core/src/main/scala/spark/scheduler/ShuffleMapTask.scala
index 27d97ffee5..966a5e173a 100644
--- a/core/src/main/scala/spark/scheduler/ShuffleMapTask.scala
+++ b/core/src/main/scala/spark/scheduler/ShuffleMapTask.scala
@@ -15,7 +15,7 @@ import com.ning.compress.lzf.LZFOutputStream
 import spark._
 import spark.storage._
 
-object ShuffleMapTask {
+private[spark] object ShuffleMapTask {
 
   // A simple map between the stage id to the serialized byte array of a task.
   // Served as a cache for task serialization because serialization can be
@@ -68,7 +68,7 @@ object ShuffleMapTask {
   }
 }
 
-class ShuffleMapTask(
+private[spark] class ShuffleMapTask(
     stageId: Int,
     var rdd: RDD[_], 
     var dep: ShuffleDependency[_,_,_],
diff --git a/core/src/main/scala/spark/scheduler/Stage.scala b/core/src/main/scala/spark/scheduler/Stage.scala
index b3ef8ac565..803dd1b97d 100644
--- a/core/src/main/scala/spark/scheduler/Stage.scala
+++ b/core/src/main/scala/spark/scheduler/Stage.scala
@@ -19,7 +19,7 @@ import spark.storage.BlockManagerId
  * Each Stage also has a priority, which is (by default) based on the job it was submitted in.
  * This allows Stages from earlier jobs to be computed first or recovered faster on failure.
  */
-class Stage(
+private[spark] class Stage(
     val id: Int,
     val rdd: RDD[_],
     val shuffleDep: Option[ShuffleDependency[_,_,_]],  // Output shuffle if stage is a map stage
diff --git a/core/src/main/scala/spark/scheduler/Task.scala b/core/src/main/scala/spark/scheduler/Task.scala
index d69c259362..d449ac67d6 100644
--- a/core/src/main/scala/spark/scheduler/Task.scala
+++ b/core/src/main/scala/spark/scheduler/Task.scala
@@ -11,7 +11,7 @@ import scala.collection.mutable.HashMap
 /**
  * A task to execute on a worker node.
  */
-abstract class Task[T](val stageId: Int) extends Serializable {
+private[spark] abstract class Task[T](val stageId: Int) extends Serializable {
   def run(attemptId: Long): T
   def preferredLocations: Seq[String] = Nil
 
@@ -25,7 +25,7 @@ abstract class Task[T](val stageId: Int) extends Serializable {
  * the task might depend on one of the JARs. Thus we serialize each task as multiple objects, by
  * first writing out its dependencies.
  */
-object Task {
+private[spark] object Task {
   /**
    * Serialize a task and the current app dependencies (files and JARs added to the SparkContext)
    */
diff --git a/core/src/main/scala/spark/scheduler/TaskResult.scala b/core/src/main/scala/spark/scheduler/TaskResult.scala
index 868ddb237c..c7b123ce7f 100644
--- a/core/src/main/scala/spark/scheduler/TaskResult.scala
+++ b/core/src/main/scala/spark/scheduler/TaskResult.scala
@@ -7,7 +7,7 @@ import scala.collection.mutable.Map
 // Task result. Also contains updates to accumulator variables.
 // TODO: Use of distributed cache to return result is a hack to get around
 // what seems to be a bug with messages over 60KB in libprocess; fix it
-class TaskResult[T](var value: T, var accumUpdates: Map[Long, Any]) extends Externalizable {
+private[spark] class TaskResult[T](var value: T, var accumUpdates: Map[Long, Any]) extends Externalizable {
   def this() = this(null.asInstanceOf[T], null)
 
   override def writeExternal(out: ObjectOutput) {
diff --git a/core/src/main/scala/spark/scheduler/TaskScheduler.scala b/core/src/main/scala/spark/scheduler/TaskScheduler.scala
index c35633d53c..d549b184b0 100644
--- a/core/src/main/scala/spark/scheduler/TaskScheduler.scala
+++ b/core/src/main/scala/spark/scheduler/TaskScheduler.scala
@@ -7,7 +7,7 @@ package spark.scheduler
  * are failures, and mitigating stragglers. They return events to the DAGScheduler through
  * the TaskSchedulerListener interface.
  */
-trait TaskScheduler {
+private[spark] trait TaskScheduler {
   def start(): Unit
 
   // Disconnect from the cluster.
diff --git a/core/src/main/scala/spark/scheduler/TaskSchedulerListener.scala b/core/src/main/scala/spark/scheduler/TaskSchedulerListener.scala
index f838272fb4..fa4de15d0d 100644
--- a/core/src/main/scala/spark/scheduler/TaskSchedulerListener.scala
+++ b/core/src/main/scala/spark/scheduler/TaskSchedulerListener.scala
@@ -7,7 +7,7 @@ import spark.TaskEndReason
 /**
  * Interface for getting events back from the TaskScheduler.
  */
-trait TaskSchedulerListener {
+private[spark] trait TaskSchedulerListener {
   // A task has finished or failed.
   def taskEnded(task: Task[_], reason: TaskEndReason, result: Any, accumUpdates: Map[Long, Any]): Unit
 
diff --git a/core/src/main/scala/spark/scheduler/TaskSet.scala b/core/src/main/scala/spark/scheduler/TaskSet.scala
index 3f4a464902..a3002ca477 100644
--- a/core/src/main/scala/spark/scheduler/TaskSet.scala
+++ b/core/src/main/scala/spark/scheduler/TaskSet.scala
@@ -4,7 +4,7 @@ package spark.scheduler
  * A set of tasks submitted together to the low-level TaskScheduler, usually representing
  * missing partitions of a particular stage.
  */
-class TaskSet(val tasks: Array[Task[_]], val stageId: Int, val attempt: Int, val priority: Int) {
+private[spark] class TaskSet(val tasks: Array[Task[_]], val stageId: Int, val attempt: Int, val priority: Int) {
   val id: String = stageId + "." + attempt
 
   override def toString: String = "TaskSet " + id
diff --git a/core/src/main/scala/spark/scheduler/cluster/ClusterScheduler.scala b/core/src/main/scala/spark/scheduler/cluster/ClusterScheduler.scala
index 16fe5761c8..f5e852d203 100644
--- a/core/src/main/scala/spark/scheduler/cluster/ClusterScheduler.scala
+++ b/core/src/main/scala/spark/scheduler/cluster/ClusterScheduler.scala
@@ -16,7 +16,7 @@ import java.util.concurrent.atomic.AtomicLong
  * The main TaskScheduler implementation, for running tasks on a cluster. Clients should first call
  * start(), then submit task sets through the runTasks method.
  */
-class ClusterScheduler(val sc: SparkContext)
+private[spark] class ClusterScheduler(val sc: SparkContext)
   extends TaskScheduler
   with Logging {
 
diff --git a/core/src/main/scala/spark/scheduler/cluster/SchedulerBackend.scala b/core/src/main/scala/spark/scheduler/cluster/SchedulerBackend.scala
index 897976c3f9..ddcd64d7c6 100644
--- a/core/src/main/scala/spark/scheduler/cluster/SchedulerBackend.scala
+++ b/core/src/main/scala/spark/scheduler/cluster/SchedulerBackend.scala
@@ -5,7 +5,7 @@ package spark.scheduler.cluster
  * ClusterScheduler. We assume a Mesos-like model where the application gets resource offers as
  * machines become available and can launch tasks on them.
  */
-trait SchedulerBackend {
+private[spark] trait SchedulerBackend {
   def start(): Unit
   def stop(): Unit
   def reviveOffers(): Unit
diff --git a/core/src/main/scala/spark/scheduler/cluster/SlaveResources.scala b/core/src/main/scala/spark/scheduler/cluster/SlaveResources.scala
index e15d577a8b..3c8f511a07 100644
--- a/core/src/main/scala/spark/scheduler/cluster/SlaveResources.scala
+++ b/core/src/main/scala/spark/scheduler/cluster/SlaveResources.scala
@@ -1,3 +1,3 @@
 package spark.scheduler.cluster
 
-class SlaveResources(val slaveId: String, val hostname: String, val coresFree: Int) {}
+private[spark] class SlaveResources(val slaveId: String, val hostname: String, val coresFree: Int) {}
diff --git a/core/src/main/scala/spark/scheduler/cluster/SparkDeploySchedulerBackend.scala b/core/src/main/scala/spark/scheduler/cluster/SparkDeploySchedulerBackend.scala
index 9093a329a3..0043dbeb10 100644
--- a/core/src/main/scala/spark/scheduler/cluster/SparkDeploySchedulerBackend.scala
+++ b/core/src/main/scala/spark/scheduler/cluster/SparkDeploySchedulerBackend.scala
@@ -5,7 +5,7 @@ import spark.deploy.client.{Client, ClientListener}
 import spark.deploy.{Command, JobDescription}
 import scala.collection.mutable.HashMap
 
-class SparkDeploySchedulerBackend(
+private[spark] class SparkDeploySchedulerBackend(
     scheduler: ClusterScheduler,
     sc: SparkContext,
     master: String,
diff --git a/core/src/main/scala/spark/scheduler/cluster/StandaloneClusterMessage.scala b/core/src/main/scala/spark/scheduler/cluster/StandaloneClusterMessage.scala
index 80e8733671..c4e8fea3dc 100644
--- a/core/src/main/scala/spark/scheduler/cluster/StandaloneClusterMessage.scala
+++ b/core/src/main/scala/spark/scheduler/cluster/StandaloneClusterMessage.scala
@@ -4,20 +4,20 @@ import spark.TaskState.TaskState
 import java.nio.ByteBuffer
 import spark.util.SerializableBuffer
 
-sealed trait StandaloneClusterMessage extends Serializable
+private[spark] sealed trait StandaloneClusterMessage extends Serializable
 
 // Master to slaves
-case class LaunchTask(task: TaskDescription) extends StandaloneClusterMessage
-case class RegisteredSlave(sparkProperties: Seq[(String, String)]) extends StandaloneClusterMessage
-case class RegisterSlaveFailed(message: String) extends StandaloneClusterMessage
+private[spark] case class LaunchTask(task: TaskDescription) extends StandaloneClusterMessage
+private[spark] case class RegisteredSlave(sparkProperties: Seq[(String, String)]) extends StandaloneClusterMessage
+private[spark] case class RegisterSlaveFailed(message: String) extends StandaloneClusterMessage
 
 // Slaves to master
-case class RegisterSlave(slaveId: String, host: String, cores: Int) extends StandaloneClusterMessage
+private[spark] case class RegisterSlave(slaveId: String, host: String, cores: Int) extends StandaloneClusterMessage
 
-case class StatusUpdate(slaveId: String, taskId: Long, state: TaskState, data: SerializableBuffer)
+private[spark] case class StatusUpdate(slaveId: String, taskId: Long, state: TaskState, data: SerializableBuffer)
   extends StandaloneClusterMessage
 
-object StatusUpdate {
+private[spark] object StatusUpdate {
   /** Alternate factory method that takes a ByteBuffer directly for the data field */
   def apply(slaveId: String, taskId: Long, state: TaskState, data: ByteBuffer): StatusUpdate = {
     StatusUpdate(slaveId, taskId, state, new SerializableBuffer(data))
@@ -25,5 +25,5 @@ object StatusUpdate {
 }
 
 // Internal messages in master
-case object ReviveOffers extends StandaloneClusterMessage
-case object StopMaster extends StandaloneClusterMessage
+private[spark] case object ReviveOffers extends StandaloneClusterMessage
+private[spark] case object StopMaster extends StandaloneClusterMessage
diff --git a/core/src/main/scala/spark/scheduler/cluster/StandaloneSchedulerBackend.scala b/core/src/main/scala/spark/scheduler/cluster/StandaloneSchedulerBackend.scala
index 83e7c6e036..8aebdedda2 100644
--- a/core/src/main/scala/spark/scheduler/cluster/StandaloneSchedulerBackend.scala
+++ b/core/src/main/scala/spark/scheduler/cluster/StandaloneSchedulerBackend.scala
@@ -16,7 +16,7 @@ import akka.remote.{RemoteClientShutdown, RemoteClientDisconnected, RemoteClient
  * Akka. These may be executed in a variety of ways, such as Mesos tasks for the coarse-grained
  * Mesos mode or standalone processes for Spark's standalone deploy mode (spark.deploy.*).
  */
-class StandaloneSchedulerBackend(scheduler: ClusterScheduler, actorSystem: ActorSystem)
+private[spark] class StandaloneSchedulerBackend(scheduler: ClusterScheduler, actorSystem: ActorSystem)
   extends SchedulerBackend with Logging {
 
   // Use an atomic variable to track total number of cores in the cluster for simplicity and speed
@@ -149,6 +149,6 @@ class StandaloneSchedulerBackend(scheduler: ClusterScheduler, actorSystem: Actor
   def defaultParallelism(): Int = math.max(totalCoreCount.get(), 2)
 }
 
-object StandaloneSchedulerBackend {
+private[spark] object StandaloneSchedulerBackend {
   val ACTOR_NAME = "StandaloneScheduler"
 }
diff --git a/core/src/main/scala/spark/scheduler/cluster/TaskDescription.scala b/core/src/main/scala/spark/scheduler/cluster/TaskDescription.scala
index f9a1b74fa5..aa097fd3a2 100644
--- a/core/src/main/scala/spark/scheduler/cluster/TaskDescription.scala
+++ b/core/src/main/scala/spark/scheduler/cluster/TaskDescription.scala
@@ -3,7 +3,7 @@ package spark.scheduler.cluster
 import java.nio.ByteBuffer
 import spark.util.SerializableBuffer
 
-class TaskDescription(
+private[spark] class TaskDescription(
     val taskId: Long,
     val slaveId: String,
     val name: String,
diff --git a/core/src/main/scala/spark/scheduler/cluster/TaskInfo.scala b/core/src/main/scala/spark/scheduler/cluster/TaskInfo.scala
index 65e59841a9..ae2c6b9836 100644
--- a/core/src/main/scala/spark/scheduler/cluster/TaskInfo.scala
+++ b/core/src/main/scala/spark/scheduler/cluster/TaskInfo.scala
@@ -3,7 +3,7 @@ package spark.scheduler.cluster
 /**
  * Information about a running task attempt inside a TaskSet.
  */
-class TaskInfo(val taskId: Long, val index: Int, val launchTime: Long, val host: String) {
+private[spark] class TaskInfo(val taskId: Long, val index: Int, val launchTime: Long, val host: String) {
   var finishTime: Long = 0
   var failed = false
 
diff --git a/core/src/main/scala/spark/scheduler/cluster/TaskSetManager.scala b/core/src/main/scala/spark/scheduler/cluster/TaskSetManager.scala
index aa37462fb0..9bb88ad6a1 100644
--- a/core/src/main/scala/spark/scheduler/cluster/TaskSetManager.scala
+++ b/core/src/main/scala/spark/scheduler/cluster/TaskSetManager.scala
@@ -17,7 +17,7 @@ import java.nio.ByteBuffer
 /**
  * Schedules the tasks within a single TaskSet in the ClusterScheduler.
  */
-class TaskSetManager(
+private[spark] class TaskSetManager(
   sched: ClusterScheduler,
   val taskSet: TaskSet)
   extends Logging {
diff --git a/core/src/main/scala/spark/scheduler/cluster/WorkerOffer.scala b/core/src/main/scala/spark/scheduler/cluster/WorkerOffer.scala
index 1e83f103e7..298b6d5529 100644
--- a/core/src/main/scala/spark/scheduler/cluster/WorkerOffer.scala
+++ b/core/src/main/scala/spark/scheduler/cluster/WorkerOffer.scala
@@ -3,5 +3,5 @@ package spark.scheduler.cluster
 /**
  * Represents free resources available on a worker node.
  */
-class WorkerOffer(val slaveId: String, val hostname: String, val cores: Int) {
+private[spark] class WorkerOffer(val slaveId: String, val hostname: String, val cores: Int) {
 }
diff --git a/core/src/main/scala/spark/scheduler/local/LocalScheduler.scala b/core/src/main/scala/spark/scheduler/local/LocalScheduler.scala
index 53fc659345..2b38d8b52e 100644
--- a/core/src/main/scala/spark/scheduler/local/LocalScheduler.scala
+++ b/core/src/main/scala/spark/scheduler/local/LocalScheduler.scala
@@ -15,7 +15,7 @@ import spark.scheduler._
  * the scheduler also allows each task to fail up to maxFailures times, which is useful for
  * testing fault recovery.
  */
-class LocalScheduler(threads: Int, maxFailures: Int, sc: SparkContext)
+private[spark] class LocalScheduler(threads: Int, maxFailures: Int, sc: SparkContext)
   extends TaskScheduler
   with Logging {
 
diff --git a/core/src/main/scala/spark/scheduler/mesos/CoarseMesosSchedulerBackend.scala b/core/src/main/scala/spark/scheduler/mesos/CoarseMesosSchedulerBackend.scala
index fdf007ffb2..9737c6b63e 100644
--- a/core/src/main/scala/spark/scheduler/mesos/CoarseMesosSchedulerBackend.scala
+++ b/core/src/main/scala/spark/scheduler/mesos/CoarseMesosSchedulerBackend.scala
@@ -24,7 +24,7 @@ import spark.TaskState
  * Unfortunately this has a bit of duplication from MesosSchedulerBackend, but it seems hard to
  * remove this.
  */
-class CoarseMesosSchedulerBackend(
+private[spark] class CoarseMesosSchedulerBackend(
     scheduler: ClusterScheduler,
     sc: SparkContext,
     master: String,
diff --git a/core/src/main/scala/spark/scheduler/mesos/MesosSchedulerBackend.scala b/core/src/main/scala/spark/scheduler/mesos/MesosSchedulerBackend.scala
index 44eda93dd1..e85e4ef318 100644
--- a/core/src/main/scala/spark/scheduler/mesos/MesosSchedulerBackend.scala
+++ b/core/src/main/scala/spark/scheduler/mesos/MesosSchedulerBackend.scala
@@ -20,7 +20,7 @@ import spark.TaskState
  * separate Mesos task, allowing multiple applications to share cluster nodes both in space (tasks
  * from multiple apps can run on different cores) and in time (a core can switch ownership).
  */
-class MesosSchedulerBackend(
+private[spark] class MesosSchedulerBackend(
     scheduler: ClusterScheduler,
     sc: SparkContext,
     master: String,
diff --git a/core/src/main/scala/spark/storage/BlockManager.scala b/core/src/main/scala/spark/storage/BlockManager.scala
index 37d5862575..bb033871b6 100644
--- a/core/src/main/scala/spark/storage/BlockManager.scala
+++ b/core/src/main/scala/spark/storage/BlockManager.scala
@@ -19,7 +19,7 @@ import com.ning.compress.lzf.{LZFInputStream, LZFOutputStream}
 import sun.nio.ch.DirectBuffer
 
 
-class BlockManagerId(var ip: String, var port: Int) extends Externalizable {
+private[spark] class BlockManagerId(var ip: String, var port: Int) extends Externalizable {
   def this() = this(null, 0)
 
   override def writeExternal(out: ObjectOutput) {
@@ -43,11 +43,11 @@ class BlockManagerId(var ip: String, var port: Int) extends Externalizable {
 }
 
 
-case class BlockException(blockId: String, message: String, ex: Exception = null)
+private[spark] case class BlockException(blockId: String, message: String, ex: Exception = null)
 extends Exception(message)
 
 
-class BlockLocker(numLockers: Int) {
+private[spark] class BlockLocker(numLockers: Int) {
   private val hashLocker = Array.fill(numLockers)(new Object())
 
   def getLock(blockId: String): Object = {
@@ -56,7 +56,7 @@ class BlockLocker(numLockers: Int) {
 }
 
 
-class BlockManager(val master: BlockManagerMaster, val serializer: Serializer, maxMemory: Long)
+private[spark] class BlockManager(val master: BlockManagerMaster, val serializer: Serializer, maxMemory: Long)
   extends Logging {
 
   case class BlockInfo(level: StorageLevel, tellMaster: Boolean)
diff --git a/core/src/main/scala/spark/storage/BlockManagerMaster.scala b/core/src/main/scala/spark/storage/BlockManagerMaster.scala
index 0c654364cd..ef76b3f470 100644
--- a/core/src/main/scala/spark/storage/BlockManagerMaster.scala
+++ b/core/src/main/scala/spark/storage/BlockManagerMaster.scala
@@ -16,14 +16,14 @@ import akka.util.duration._
 import spark.{Logging, SparkException, Utils}
 
 
-sealed trait ToBlockManagerMaster
+private[spark] sealed trait ToBlockManagerMaster
 
-case class RegisterBlockManager(
+private[spark] case class RegisterBlockManager(
     blockManagerId: BlockManagerId,
     maxMemSize: Long)
   extends ToBlockManagerMaster
 
-class HeartBeat(
+private[spark] class HeartBeat(
     var blockManagerId: BlockManagerId,
     var blockId: String,
     var storageLevel: StorageLevel,
@@ -53,7 +53,7 @@ class HeartBeat(
   }
 }
 
-object HeartBeat {
+private[spark] object HeartBeat {
   def apply(blockManagerId: BlockManagerId,
       blockId: String,
       storageLevel: StorageLevel,
@@ -68,18 +68,18 @@ object HeartBeat {
   }
 }
   
-case class GetLocations(blockId: String) extends ToBlockManagerMaster
+private[spark] case class GetLocations(blockId: String) extends ToBlockManagerMaster
 
-case class GetLocationsMultipleBlockIds(blockIds: Array[String]) extends ToBlockManagerMaster
+private[spark] case class GetLocationsMultipleBlockIds(blockIds: Array[String]) extends ToBlockManagerMaster
   
-case class GetPeers(blockManagerId: BlockManagerId, size: Int) extends ToBlockManagerMaster
+private[spark] case class GetPeers(blockManagerId: BlockManagerId, size: Int) extends ToBlockManagerMaster
   
-case class RemoveHost(host: String) extends ToBlockManagerMaster
+private[spark] case class RemoveHost(host: String) extends ToBlockManagerMaster
 
-case object StopBlockManagerMaster extends ToBlockManagerMaster
+private[spark] case object StopBlockManagerMaster extends ToBlockManagerMaster
 
 
-class BlockManagerMasterActor(val isLocal: Boolean) extends Actor with Logging {
+private[spark] class BlockManagerMasterActor(val isLocal: Boolean) extends Actor with Logging {
   
   class BlockManagerInfo(
       val blockManagerId: BlockManagerId,
@@ -330,7 +330,7 @@ class BlockManagerMasterActor(val isLocal: Boolean) extends Actor with Logging {
   }
 }
 
-class BlockManagerMaster(actorSystem: ActorSystem, isMaster: Boolean, isLocal: Boolean)
+private[spark] class BlockManagerMaster(actorSystem: ActorSystem, isMaster: Boolean, isLocal: Boolean)
   extends Logging {
 
   val AKKA_ACTOR_NAME: String = "BlockMasterManager"
diff --git a/core/src/main/scala/spark/storage/BlockManagerWorker.scala b/core/src/main/scala/spark/storage/BlockManagerWorker.scala
index 47e4d14010..f72079e267 100644
--- a/core/src/main/scala/spark/storage/BlockManagerWorker.scala
+++ b/core/src/main/scala/spark/storage/BlockManagerWorker.scala
@@ -17,7 +17,7 @@ import spark.network._
  *
  * TODO: Use event model.
  */
-class BlockManagerWorker(val blockManager: BlockManager) extends Logging {
+private[spark] class BlockManagerWorker(val blockManager: BlockManager) extends Logging {
   initLogging()
   
   blockManager.connectionManager.onReceiveMessage(onBlockMessageReceive)
@@ -87,7 +87,7 @@ class BlockManagerWorker(val blockManager: BlockManager) extends Logging {
   }
 }
 
-object BlockManagerWorker extends Logging {
+private[spark] object BlockManagerWorker extends Logging {
   private var blockManagerWorker: BlockManagerWorker = null
   private val DATA_TRANSFER_TIME_OUT_MS: Long = 500
   private val REQUEST_RETRY_INTERVAL_MS: Long = 1000
diff --git a/core/src/main/scala/spark/storage/BlockMessage.scala b/core/src/main/scala/spark/storage/BlockMessage.scala
index 4b5cfebba2..3f234df654 100644
--- a/core/src/main/scala/spark/storage/BlockMessage.scala
+++ b/core/src/main/scala/spark/storage/BlockMessage.scala
@@ -8,11 +8,11 @@ import scala.collection.mutable.ArrayBuffer
 import spark._
 import spark.network._
 
-case class GetBlock(id: String)
-case class GotBlock(id: String, data: ByteBuffer)
-case class PutBlock(id: String, data: ByteBuffer, level: StorageLevel) 
+private[spark] case class GetBlock(id: String)
+private[spark] case class GotBlock(id: String, data: ByteBuffer)
+private[spark] case class PutBlock(id: String, data: ByteBuffer, level: StorageLevel) 
 
-class BlockMessage() {
+private[spark] class BlockMessage() {
   // Un-initialized: typ = 0
   // GetBlock: typ = 1
   // GotBlock: typ = 2
@@ -158,7 +158,7 @@ class BlockMessage() {
   }
 }
 
-object BlockMessage {
+private[spark] object BlockMessage {
   val TYPE_NON_INITIALIZED: Int = 0
   val TYPE_GET_BLOCK: Int = 1
   val TYPE_GOT_BLOCK: Int = 2
diff --git a/core/src/main/scala/spark/storage/BlockMessageArray.scala b/core/src/main/scala/spark/storage/BlockMessageArray.scala
index 64acc7eb47..8cf7565be7 100644
--- a/core/src/main/scala/spark/storage/BlockMessageArray.scala
+++ b/core/src/main/scala/spark/storage/BlockMessageArray.scala
@@ -8,7 +8,7 @@ import scala.collection.mutable.ArrayBuffer
 import spark._
 import spark.network._
 
-class BlockMessageArray(var blockMessages: Seq[BlockMessage]) extends Seq[BlockMessage] with Logging {
+private[spark] class BlockMessageArray(var blockMessages: Seq[BlockMessage]) extends Seq[BlockMessage] with Logging {
   
   def this(bm: BlockMessage) = this(Array(bm))
 
@@ -85,7 +85,7 @@ class BlockMessageArray(var blockMessages: Seq[BlockMessage]) extends Seq[BlockM
   }
 }
 
-object BlockMessageArray {
+private[spark] object BlockMessageArray {
  
   def fromBufferMessage(bufferMessage: BufferMessage): BlockMessageArray = {
     val newBlockMessageArray = new BlockMessageArray()
diff --git a/core/src/main/scala/spark/storage/StorageLevel.scala b/core/src/main/scala/spark/storage/StorageLevel.scala
index 2d52fac1ef..2237ce92b3 100644
--- a/core/src/main/scala/spark/storage/StorageLevel.scala
+++ b/core/src/main/scala/spark/storage/StorageLevel.scala
@@ -2,7 +2,7 @@ package spark.storage
 
 import java.io.{Externalizable, ObjectInput, ObjectOutput}
 
-class StorageLevel(
+private[spark] class StorageLevel(
     var useDisk: Boolean, 
     var useMemory: Boolean,
     var deserialized: Boolean,
@@ -63,7 +63,7 @@ class StorageLevel(
     "StorageLevel(%b, %b, %b, %d)".format(useDisk, useMemory, deserialized, replication)
 }
 
-object StorageLevel {
+private[spark] object StorageLevel {
   val NONE = new StorageLevel(false, false, false)
   val DISK_ONLY = new StorageLevel(true, false, false)
   val DISK_ONLY_2 = new StorageLevel(true, false, false, 2)
diff --git a/core/src/main/scala/spark/util/AkkaUtils.scala b/core/src/main/scala/spark/util/AkkaUtils.scala
index df4e23bfd6..f670ccb709 100644
--- a/core/src/main/scala/spark/util/AkkaUtils.scala
+++ b/core/src/main/scala/spark/util/AkkaUtils.scala
@@ -17,7 +17,7 @@ import java.util.concurrent.TimeoutException
 /**
  * Various utility classes for working with Akka.
  */
-object AkkaUtils {
+private[spark] object AkkaUtils {
   /**
    * Creates an ActorSystem ready for remoting, with various Spark features. Returns both the
    * ActorSystem itself and its port (which is hard to get from Akka).
diff --git a/core/src/main/scala/spark/util/IntParam.scala b/core/src/main/scala/spark/util/IntParam.scala
index c3ff063569..0427646747 100644
--- a/core/src/main/scala/spark/util/IntParam.scala
+++ b/core/src/main/scala/spark/util/IntParam.scala
@@ -3,7 +3,7 @@ package spark.util
 /**
  * An extractor object for parsing strings into integers.
  */
-object IntParam {
+private[spark] object IntParam {
   def unapply(str: String): Option[Int] = {
     try {
       Some(str.toInt)
diff --git a/core/src/main/scala/spark/util/MemoryParam.scala b/core/src/main/scala/spark/util/MemoryParam.scala
index 4fba914afe..3726738842 100644
--- a/core/src/main/scala/spark/util/MemoryParam.scala
+++ b/core/src/main/scala/spark/util/MemoryParam.scala
@@ -6,7 +6,7 @@ import spark.Utils
  * An extractor object for parsing JVM memory strings, such as "10g", into an Int representing
  * the number of megabytes. Supports the same formats as Utils.memoryStringToMb.
  */
-object MemoryParam {
+private[spark] object MemoryParam {
   def unapply(str: String): Option[Int] = {
     try {
       Some(Utils.memoryStringToMb(str))
diff --git a/core/src/main/scala/spark/util/SerializableBuffer.scala b/core/src/main/scala/spark/util/SerializableBuffer.scala
index 0830843a77..b6e153b00b 100644
--- a/core/src/main/scala/spark/util/SerializableBuffer.scala
+++ b/core/src/main/scala/spark/util/SerializableBuffer.scala
@@ -8,7 +8,7 @@ import java.nio.channels.Channels
  * A wrapper around a java.nio.ByteBuffer that is serializable through Java serialization, to make
  * it easier to pass ByteBuffers in case class messages.
  */
-class SerializableBuffer(@transient var buffer: ByteBuffer) extends Serializable {
+private[spark] class SerializableBuffer(@transient var buffer: ByteBuffer) extends Serializable {
   def value = buffer
 
   private def readObject(in: ObjectInputStream) {
diff --git a/core/src/main/scala/spark/util/StatCounter.scala b/core/src/main/scala/spark/util/StatCounter.scala
index 11d7939204..101895f08e 100644
--- a/core/src/main/scala/spark/util/StatCounter.scala
+++ b/core/src/main/scala/spark/util/StatCounter.scala
@@ -5,7 +5,7 @@ package spark.util
  * numerically robust way. Includes support for merging two StatCounters. Based on Welford and
  * Chan's algorithms described at http://en.wikipedia.org/wiki/Algorithms_for_calculating_variance.
  */
-class StatCounter(values: TraversableOnce[Double]) extends Serializable {
+private[spark] class StatCounter(values: TraversableOnce[Double]) extends Serializable {
   private var n: Long = 0     // Running count of our values
   private var mu: Double = 0  // Running mean of our values
   private var m2: Double = 0  // Running variance numerator (sum of (x - mean)^2)
@@ -82,7 +82,7 @@ class StatCounter(values: TraversableOnce[Double]) extends Serializable {
   }
 }
 
-object StatCounter {
+private[spark] object StatCounter {
   def apply(values: TraversableOnce[Double]) = new StatCounter(values)
 
   def apply(values: Double*) = new StatCounter(values)