[SPARK-11663][STREAMING] Add Java API for trackStateByKey

TODO
- [x] Add Java API
- [x] Add API tests
- [x] Add a function test

Author: Shixiong Zhu <shixiong@databricks.com>

Closes #9636 from zsxwing/java-track.

1 files changed, 27 insertions, 0 deletions

diff --git a/core/src/main/java/org/apache/spark/api/java/function/Function4.java b/core/src/main/java/org/apache/spark/api/java/function/Function4.java
new file mode 100644
index 0000000000..fd727d6486
--- /dev/null
+++ b/core/src/main/java/org/apache/spark/api/java/function/Function4.java
@@ -0,0 +1,27 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.api.java.function;
+
+import java.io.Serializable;
+
+/**
+ * A four-argument function that takes arguments of type T1, T2, T3 and T4 and returns an R.
+ */
+public interface Function4<T1, T2, T3, T4, R> extends Serializable {
+  public R call(T1 v1, T2 v2, T3 v3, T4 v4) throws Exception;
+}