Java examples, tests for KMeans and ALS

- Changes ALS to accept RDD[Rating] instead of (Int, Int, Double) making it
  easier to call from Java
- Renames class methods from `train` to `run` to enable static methods to be
  called from Java.
- Add unit tests which check if both static / class methods can be called.
- Also add examples which port the main() function in ALS, KMeans to the
  examples project.

Couple of minor changes to existing code:
- Add a toJavaRDD method in RDD to convert scala RDD to java RDD easily
- Workaround a bug where using double[] from Java leads to class cast exception in
  KMeans init

3 files changed, 180 insertions, 0 deletions

diff --git a/examples/pom.xml b/examples/pom.xml
index 7a8d08fade..ad615b68ff 100644
--- a/examples/pom.xml
+++ b/examples/pom.xml
@@ -119,6 +119,12 @@
           <classifier>hadoop1</classifier>
         </dependency>
         <dependency>
+          <groupId>org.spark-project</groupId>
+          <artifactId>spark-mllib</artifactId>
+          <version>${project.version}</version>
+          <classifier>hadoop1</classifier>
+        </dependency>
+        <dependency>
           <groupId>org.apache.hadoop</groupId>
           <artifactId>hadoop-core</artifactId>
           <scope>provided</scope>
@@ -157,6 +163,12 @@
           <classifier>hadoop2</classifier>
         </dependency>
         <dependency>
+          <groupId>org.spark-project</groupId>
+          <artifactId>spark-mllib</artifactId>
+          <version>${project.version}</version>
+          <classifier>hadoop2</classifier>
+        </dependency>
+        <dependency>
           <groupId>org.apache.hadoop</groupId>
           <artifactId>hadoop-core</artifactId>
           <scope>provided</scope>
diff --git a/examples/src/main/java/spark/mllib/JavaALS.java b/examples/src/main/java/spark/mllib/JavaALS.java
new file mode 100644
index 0000000000..8be079ad39
--- /dev/null
+++ b/examples/src/main/java/spark/mllib/JavaALS.java
@@ -0,0 +1,87 @@
+/*
+ * 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 spark.mllib.examples;
+
+import spark.api.java.JavaRDD;
+import spark.api.java.JavaSparkContext;
+import spark.api.java.function.Function;
+
+import spark.mllib.recommendation.ALS;
+import spark.mllib.recommendation.MatrixFactorizationModel;
+import spark.mllib.recommendation.Rating;
+
+import java.io.Serializable;
+import java.util.Arrays;
+import java.util.StringTokenizer;
+
+import scala.Tuple2;
+
+/**
+ * Example using MLLib ALS from Java.
+ */
+public class  JavaALS {
+
+  static class ParseRating extends Function<String, Rating> {
+    public Rating call(String line) {
+      StringTokenizer tok = new StringTokenizer(line, ",");
+      Integer x = Integer.parseInt(tok.nextToken());
+      Integer y = Integer.parseInt(tok.nextToken());
+      Double rating = Double.parseDouble(tok.nextToken());
+      return new Rating(x, y, rating);
+    }
+  }
+
+  static class FeaturesToString extends Function<Tuple2<Object, double[]>, String> {
+    public String call(Tuple2<Object, double[]> element) {
+      return element._1().toString() + "," + Arrays.toString(element._2());
+    }
+  }
+
+  public static void main(String[] args) {
+
+    if (args.length != 5 && args.length != 6) {
+      System.err.println(
+          "Usage: JavaALS <master> <ratings_file> <rank> <iterations> <output_dir> [<blocks>]");
+      System.exit(1);
+    }
+
+    int rank = Integer.parseInt(args[2]);
+    int iterations = Integer.parseInt(args[3]);
+    String outputDir = args[4];
+    int blocks = -1;
+    if (args.length == 6) {
+      blocks = Integer.parseInt(args[5]);
+    }
+
+    JavaSparkContext sc = new JavaSparkContext(args[0], "JavaALS",
+        System.getenv("SPARK_HOME"), System.getenv("SPARK_EXAMPLES_JAR"));
+    JavaRDD<String> lines = sc.textFile(args[1]);
+
+    JavaRDD<Rating> ratings = lines.map(new ParseRating());
+
+    MatrixFactorizationModel model = ALS.train(ratings.rdd(), rank, iterations, 0.01, blocks);
+
+    model.userFeatures().toJavaRDD().map(new FeaturesToString()).saveAsTextFile(
+        outputDir + "/userFeatures");
+    model.productFeatures().toJavaRDD().map(new FeaturesToString()).saveAsTextFile(
+        outputDir + "/productFeatures");
+    System.out.println("Final user/product features written to " + outputDir);
+
+    System.exit(0);
+  }
+}
diff --git a/examples/src/main/java/spark/mllib/JavaKMeans.java b/examples/src/main/java/spark/mllib/JavaKMeans.java
new file mode 100644
index 0000000000..02f40438b8
--- /dev/null
+++ b/examples/src/main/java/spark/mllib/JavaKMeans.java
@@ -0,0 +1,81 @@
+/*
+ * 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 spark.mllib.examples;
+
+import spark.api.java.JavaRDD;
+import spark.api.java.JavaSparkContext;
+import spark.api.java.function.Function;
+
+import spark.mllib.clustering.KMeans;
+import spark.mllib.clustering.KMeansModel;
+
+import java.util.Arrays;
+import java.util.StringTokenizer;
+
+/**
+ * Example using MLLib KMeans from Java.
+ */
+public class JavaKMeans {
+
+  static class ParsePoint extends Function<String, double[]> {
+    public double[] call(String line) {
+      StringTokenizer tok = new StringTokenizer(line, " ");
+      int numTokens = tok.countTokens();
+      double[] point = new double[numTokens];
+      for (int i = 0; i < numTokens; ++i) {
+        point[i] = Double.parseDouble(tok.nextToken());
+      }
+      return point;
+    }
+  }
+
+  public static void main(String[] args) {
+
+    if (args.length < 4) {
+      System.err.println(
+          "Usage: JavaKMeans <master> <input_file> <k> <max_iterations> [<runs>]");
+      System.exit(1);
+    }
+
+    String inputFile = args[1];
+    int k = Integer.parseInt(args[2]);
+    int iterations = Integer.parseInt(args[3]);
+    int runs = 1;
+
+    if (args.length >= 5) {
+      runs = Integer.parseInt(args[4]);
+    }
+
+    JavaSparkContext sc = new JavaSparkContext(args[0], "JavaKMeans",
+        System.getenv("SPARK_HOME"), System.getenv("SPARK_EXAMPLES_JAR"));
+    JavaRDD<String> lines = sc.textFile(args[1]);
+
+    JavaRDD<double[]> points = lines.map(new ParsePoint());
+
+    KMeansModel model = KMeans.train(points.rdd(), k, iterations, runs);
+
+    System.out.println("Cluster centers:");
+    for (double[] center : model.clusterCenters()) {
+      System.out.println(" " + Arrays.toString(center));
+    }
+    double cost = model.computeCost(points.rdd());
+    System.out.println("Cost: " + cost);
+
+    System.exit(0);
+  }
+}