Change "Duration" to "Durations" to avoid changing Duration case clas…

…s API

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

@@ -100,13 +100,23 @@ object Minutes {
 }
 
 // Java-friendlier versions of the objects above.
+// Named "Durations" instead of "Duration" to avoid changing the case class's implied API.
 
-object Duration {
+object Durations {
 
-  // No 'milliseconds' since it would conflict with methods above. Use the constructor directly.
+  /**
+   * @return [[org.apache.spark.streaming.Duration]] representing given number of milliseconds.
+   */
+  def milliseconds(milliseconds: Long) = Milliseconds(milliseconds)
 
+  /**
+   * @return [[org.apache.spark.streaming.Duration]] representing given number of seconds.
+   */
   def seconds(seconds: Long) = Seconds(seconds)
 
+  /**
+   * @return [[org.apache.spark.streaming.Duration]] representing given number of minutes.
+   */
   def minutes(minutes: Long) = Minutes(minutes)
 
 }

streaming/src/test/java/org/apache/spark/streaming/JavaDurationSuite.java

@@ -66,14 +66,19 @@ public void testDiv() {
     Assert.assertEquals(200.0, new Duration(1000).div(new Duration(5)), 1.0e-12);
   }
 
+  @Test
+  public void testMilliseconds() {
+    Assert.assertEquals(new Duration(100), Durations.milliseconds(100));
+  }
+
   @Test
   public void testSeconds() {
-    Assert.assertEquals(new Duration(30 * 1000), Duration.seconds(30));
+    Assert.assertEquals(new Duration(30 * 1000), Durations.seconds(30));
   }
 
   @Test
   public void testMinutes() {
-    Assert.assertEquals(new Duration(2 * 60 * 1000), Duration.minutes(2));
+    Assert.assertEquals(new Duration(2 * 60 * 1000), Durations.minutes(2));
   }
 
 }