[java8API] SPARK-964 Investigate the potential for using JDK 8 lambda expressions for the Java/Scala APIs

Author: Prashant Sharma <prashant.s@imaginea.com>
Author: Patrick Wendell <pwendell@gmail.com>

Closes #17 from ScrapCodes/java8-lambdas and squashes the following commits:

95850e6 [Patrick Wendell] Some doc improvements and build changes to the Java 8 patch.
85a954e [Prashant Sharma] Nit. import orderings.
673f7ac [Prashant Sharma] Added support for -java-home as well
80a13e8 [Prashant Sharma] Used fake class tag syntax
26eb3f6 [Prashant Sharma] Patrick's comments on PR.
35d8d79 [Prashant Sharma] Specified java 8 building in the docs
31d4cd6 [Prashant Sharma] Maven build to support -Pjava8-tests flag.
4ab87d3 [Prashant Sharma] Review feedback on the pr
c33dc2c [Prashant Sharma] SPARK-964, Java 8 API Support.

10 files changed, 277 insertions, 0 deletions

diff --git a/core/src/main/java/org/apache/spark/api/java/function/DoubleFlatMapFunction.java b/core/src/main/java/org/apache/spark/api/java/function/DoubleFlatMapFunction.java
new file mode 100644
index 0000000000..57fd0a7a80
--- /dev/null
+++ b/core/src/main/java/org/apache/spark/api/java/function/DoubleFlatMapFunction.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 function that returns zero or more records of type Double from each input record.
+ */
+public interface DoubleFlatMapFunction<T> extends Serializable {
+  public Iterable<Double> call(T t) throws Exception;
+}
diff --git a/core/src/main/java/org/apache/spark/api/java/function/DoubleFunction.java b/core/src/main/java/org/apache/spark/api/java/function/DoubleFunction.java
new file mode 100644
index 0000000000..150144e0e4
--- /dev/null
+++ b/core/src/main/java/org/apache/spark/api/java/function/DoubleFunction.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 function that returns Doubles, and can be used to construct DoubleRDDs.
+ */
+public interface DoubleFunction<T> extends Serializable {
+  public double call(T t) throws Exception;
+}
diff --git a/core/src/main/java/org/apache/spark/api/java/function/FlatMapFunction.java b/core/src/main/java/org/apache/spark/api/java/function/FlatMapFunction.java
new file mode 100644
index 0000000000..fa75842047
--- /dev/null
+++ b/core/src/main/java/org/apache/spark/api/java/function/FlatMapFunction.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 function that returns zero or more output records from each input record.
+ */
+public interface FlatMapFunction<T, R> extends Serializable {
+  public Iterable<R> call(T t) throws Exception;
+}
\ No newline at end of file
diff --git a/core/src/main/java/org/apache/spark/api/java/function/FlatMapFunction2.java b/core/src/main/java/org/apache/spark/api/java/function/FlatMapFunction2.java
new file mode 100644
index 0000000000..d1fdec0724
--- /dev/null
+++ b/core/src/main/java/org/apache/spark/api/java/function/FlatMapFunction2.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 function that takes two inputs and returns zero or more output records.
+ */
+public interface FlatMapFunction2<T1, T2, R> extends Serializable {
+  public Iterable<R> call(T1 t1, T2 t2) throws Exception;
+}
\ No newline at end of file
diff --git a/core/src/main/java/org/apache/spark/api/java/function/Function.java b/core/src/main/java/org/apache/spark/api/java/function/Function.java
new file mode 100644
index 0000000000..d00551bb0a
--- /dev/null
+++ b/core/src/main/java/org/apache/spark/api/java/function/Function.java
@@ -0,0 +1,29 @@
+/*
+ * 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;
+
+/**
+ * Base interface for functions whose return types do not create special RDDs. PairFunction and
+ * DoubleFunction are handled separately, to allow PairRDDs and DoubleRDDs to be constructed
+ * when mapping RDDs of other types.
+ */
+public interface Function<T1, R> extends Serializable {
+  public R call(T1 v1) throws Exception;
+}
diff --git a/core/src/main/java/org/apache/spark/api/java/function/Function2.java b/core/src/main/java/org/apache/spark/api/java/function/Function2.java
new file mode 100644
index 0000000000..793caaa61a
--- /dev/null
+++ b/core/src/main/java/org/apache/spark/api/java/function/Function2.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 two-argument function that takes arguments of type T1 and T2 and returns an R.
+ */
+public interface Function2<T1, T2, R> extends Serializable {
+  public R call(T1 v1, T2 v2) throws Exception;
+}
diff --git a/core/src/main/java/org/apache/spark/api/java/function/Function3.java b/core/src/main/java/org/apache/spark/api/java/function/Function3.java
new file mode 100644
index 0000000000..b4151c3417
--- /dev/null
+++ b/core/src/main/java/org/apache/spark/api/java/function/Function3.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 three-argument function that takes arguments of type T1, T2 and T3 and returns an R.
+ */
+public interface Function3<T1, T2, T3, R> extends Serializable {
+  public R call(T1 v1, T2 v2, T3 v3) throws Exception;
+}
diff --git a/core/src/main/java/org/apache/spark/api/java/function/PairFlatMapFunction.java b/core/src/main/java/org/apache/spark/api/java/function/PairFlatMapFunction.java
new file mode 100644
index 0000000000..691ef2eceb
--- /dev/null
+++ b/core/src/main/java/org/apache/spark/api/java/function/PairFlatMapFunction.java
@@ -0,0 +1,30 @@
+/*
+ * 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;
+
+import scala.Tuple2;
+
+/**
+ * A function that returns zero or more key-value pair records from each input record. The
+ * key-value pairs are represented as scala.Tuple2 objects.
+ */
+public interface PairFlatMapFunction<T, K, V> extends Serializable {
+  public Iterable<Tuple2<K, V>> call(T t) throws Exception;
+}
diff --git a/core/src/main/java/org/apache/spark/api/java/function/PairFunction.java b/core/src/main/java/org/apache/spark/api/java/function/PairFunction.java
new file mode 100644
index 0000000000..abd9bcc07a
--- /dev/null
+++ b/core/src/main/java/org/apache/spark/api/java/function/PairFunction.java
@@ -0,0 +1,29 @@
+/*
+ * 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;
+
+import scala.Tuple2;
+
+/**
+ * A function that returns key-value pairs (Tuple2<K, V>), and can be used to construct PairRDDs.
+ */
+public interface PairFunction<T, K, V> extends Serializable {
+  public Tuple2<K, V> call(T t) throws Exception;
+}
diff --git a/core/src/main/java/org/apache/spark/api/java/function/VoidFunction.java b/core/src/main/java/org/apache/spark/api/java/function/VoidFunction.java
new file mode 100644
index 0000000000..2a10435b75
--- /dev/null
+++ b/core/src/main/java/org/apache/spark/api/java/function/VoidFunction.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 function with no return value.
+ */
+public interface VoidFunction<T> extends Serializable {
+  public void call(T t) throws Exception;
+}