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/*
 * 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.examples.ml;

import org.apache.spark.SparkConf;
import org.apache.spark.api.java.JavaSparkContext;
import org.apache.spark.sql.SQLContext;

// $example on$
import java.util.Arrays;

import org.apache.spark.api.java.JavaRDD;
import org.apache.spark.ml.feature.NGram;
import org.apache.spark.sql.DataFrame;
import org.apache.spark.sql.Row;
import org.apache.spark.sql.RowFactory;
import org.apache.spark.sql.types.DataTypes;
import org.apache.spark.sql.types.Metadata;
import org.apache.spark.sql.types.StructField;
import org.apache.spark.sql.types.StructType;
// $example off$

public class JavaNGramExample {
  public static void main(String[] args) {
    SparkConf conf = new SparkConf().setAppName("JavaNGramExample");
    JavaSparkContext jsc = new JavaSparkContext(conf);
    SQLContext sqlContext = new SQLContext(jsc);

    // $example on$
    JavaRDD jrdd = jsc.parallelize(Arrays.asList(
      RowFactory.create(0.0, Arrays.asList("Hi", "I", "heard", "about", "Spark")),
      RowFactory.create(1.0, Arrays.asList("I", "wish", "Java", "could", "use", "case", "classes")),
      RowFactory.create(2.0, Arrays.asList("Logistic", "regression", "models", "are", "neat"))
    ));

    StructType schema = new StructType(new StructField[]{
      new StructField("label", DataTypes.DoubleType, false, Metadata.empty()),
      new StructField(
        "words", DataTypes.createArrayType(DataTypes.StringType), false, Metadata.empty())
    });

    DataFrame wordDataFrame = sqlContext.createDataFrame(jrdd, schema);

    NGram ngramTransformer = new NGram().setInputCol("words").setOutputCol("ngrams");

    DataFrame ngramDataFrame = ngramTransformer.transform(wordDataFrame);

    for (Row r : ngramDataFrame.select("ngrams", "label").take(3)) {
      java.util.List ngrams = r.getList(0);
      for (String ngram : ngrams) System.out.print(ngram + " --- ");
      System.out.println();
    }
    // $example off$
    jsc.stop();
  }
}