add createStream method with replicationFactor parameter (#35)

Author: daleiz

client/src/main/java/io/hstream/HStreamClient.java

@@ -20,9 +20,20 @@ static HStreamClientBuilder builder() {
   /** @return the {@link QueryerBuilder}. */
   QueryerBuilder newQueryer();
 
-  /** @param stream the name of stream. */
+  /**
+   * create a new stream with 3 replicas.
+   *
+   * @param stream the name of stream.
+   */
   void createStream(String stream);
 
+  /**
+   * create a new stream.
+   *
+   * @param stream the name of stream.
+   */
+  void createStream(String stream, short replicationFactor);
+
   /**
    * Delete specified stream with streamName.
    *

client/src/main/java/io/hstream/impl/HStreamClientImpl.java

@@ -23,6 +23,8 @@ public class HStreamClientImpl implements HStreamClient {
   private final HStreamApiGrpc.HStreamApiStub stub;
   private final HStreamApiGrpc.HStreamApiBlockingStub blockingStub;
 
+  private static final short DEFAULT_STREAM_REPLICATOR = 3;
+
   public HStreamClientImpl(String serviceUrl) {
     ManagedChannel channel = ManagedChannelBuilder.forTarget(serviceUrl).usePlaintext().build();
     this.managedChannel = channel;
@@ -47,8 +49,12 @@ public QueryerBuilder newQueryer() {
 
   @Override
   public void createStream(String streamName) {
-    Stream stream = new Stream(streamName, 3);
+    createStream(streamName, DEFAULT_STREAM_REPLICATOR);
+  }
 
+  @Override
+  public void createStream(String streamName, short replicationFactor) {
+    Stream stream = new Stream(streamName, replicationFactor);
     blockingStub.createStream(GrpcUtils.streamToGrpc(stream));
   }