[Streaming] Streaming filter transform (#6816)

* add filter transform

* lint

* add new line

streaming/java/streaming-runtime/src/test/java/org/ray/streaming/runtime/demo/WordCountTest.java

@@ -44,6 +44,7 @@ public class WordCountTest extends BaseUnitTest implements Serializable {
             collector.collect(new WordAndCount(record, 1));
           }
         })
+        .filter(pair -> !pair.word.contains("world"))
         .keyBy(pair -> pair.word)
         .reduce((ReduceFunction<WordAndCount>) (oldValue, newValue) ->
             new WordAndCount(oldValue.word, oldValue.count + newValue.count))
@@ -53,14 +54,14 @@ public class WordCountTest extends BaseUnitTest implements Serializable {
     streamingContext.execute("testWordCount");
 
     // Sleep until the count for every word is computed.
-    while (wordCount.size() < 3) {
+    while (wordCount.size() < 2) {
       try {
         Thread.sleep(100);
       } catch (InterruptedException e) {
         LOGGER.warn("Got an exception while sleeping.", e);
       }
     }
-    Assert.assertEquals(wordCount, ImmutableMap.of("eagle", 3, "hello", 1, "world", 1));
+    Assert.assertEquals(wordCount, ImmutableMap.of("eagle", 3, "hello", 1));
   }
 
   private static class WordAndCount implements Serializable {