Added more docs

Author: tdas

streaming/src/main/scala/org/apache/spark/streaming/StreamingContext.scala

@@ -513,7 +513,12 @@ class StreamingContext private[streaming] (
   /**
    * :: DeveloperApi ::
    *
-   * Return the current state of the context.
+   * Return the current state of the context. The context can be in three possible states -
+   * - StreamingContextState.INTIALIZED - The context has been created, but not been started yet.
+   *   Input DStreams, transformations and output operations can be created on the context.
+   * - StreamingContextState.STARTED - The context has been started, and been not stopped.
+   *   Input DStreams, transformations and output operations cannot be created on the context.
+   * - StreamingContextState.STOPPED - The context has been stopped and cannot be used any more.
    */
   @DeveloperApi
   def getState(): StreamingContextState = {

streaming/src/main/scala/org/apache/spark/streaming/StreamingContextState.java

@@ -22,9 +22,24 @@
 /**
  * :: DeveloperApi ::
  *
- * Represents the state of the StreamingContext.
+ * Represents the state of a StreamingContext.
  */
 @DeveloperApi
 public enum StreamingContextState {
-  INITIALIZED, STARTED, STOPPED
+  /**
+   * The context has been created, but not been started yet.
+   * Input DStreams, transformations and output operations can be created on the context.
+   */
+  INITIALIZED,
+
+  /**
+   * The context has been started, and been not stopped.
+   * Input DStreams, transformations and output operations cannot be created on the context.
+   */
+  STARTED,
+
+  /**
+   * The context has been stopped and cannot be used any more.
+   */
+  STOPPED
 }

streaming/src/main/scala/org/apache/spark/streaming/api/java/JavaStreamingContext.scala

@@ -581,7 +581,20 @@ class JavaStreamingContext(val ssc: StreamingContext) extends Closeable {
   /**
    * :: DeveloperApi ::
    *
-   * Return the current state of the context.
+   * Return the current state of the context. The context can be in three possible states -
+   * <ul>
+   *   <li>
+   *   StreamingContextState.INTIALIZED - The context has been created, but not been started yet.
+   *   Input DStreams, transformations and output operations can be created on the context.
+   *   </li>
+   *   <li>
+   *   StreamingContextState.STARTED - The context has been started, and been not stopped.
+   *   Input DStreams, transformations and output operations cannot be created on the context.
+   *   </li>
+   *   <li>
+   *   StreamingContextState.STOPPED - The context has been stopped and cannot be used any more.
+   *   </li>
+   * </ul>
    */
   def getState(): StreamingContextState = {
     ssc.getState()