computes a simple word occurrence histogram over some sample data using apache flink - Java Big Data

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Description

computes a simple word occurrence histogram over some sample data using apache flink

Demo Code


/**/*  w  w w .  ja v  a 2s.com*/
 * 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.
 */

import org.apache.flink.api.java.DataSet;
import org.apache.flink.api.java.ExecutionEnvironment;
import org.apache.flink.api.common.functions.FlatMapFunction;
import org.apache.flink.api.java.tuple.Tuple2;
import org.apache.flink.util.Collector;

/**
 * Implements the "WordCount" program that computes a simple word occurrence histogram
 * over some sample data
 *
 * <p>
 * This example shows how to:
 * <ul>
 * <li>write a simple Flink program.
 * <li>use Tuple data types.
 * <li>write and use user-defined functions.
 * </ul>
 *
 */
public class WordCount {

    //
    //  Program
    //

    public static void main(String[] args) throws Exception {

        // set up the execution environment
        final ExecutionEnvironment env = ExecutionEnvironment
                .getExecutionEnvironment();

        // get input data
        DataSet<String> text = env.fromElements(
                "To be, or not to be,--that is the question:--",
                "Whether 'tis nobler in the mind to suffer",
                "The slings and arrows of outrageous fortune",
                "Or to take arms against a sea of troubles,");

        DataSet<Tuple2<String, Integer>> counts =
        // split up the lines in pairs (2-tuples) containing: (word,1)
        text.flatMap(new LineSplitter())
        // group by the tuple field "0" and sum up tuple field "1"
                .groupBy(0).sum(1);

        // execute and print result
        counts.print();

    }

    //
    //   User Functions
    //

    /**
     * Implements the string tokenizer that splits sentences into words as a user-defined
     * FlatMapFunction. The function takes a line (String) and splits it into
     * multiple pairs in the form of "(word,1)" (Tuple2<String, Integer>).
     */
    public static final class LineSplitter implements
            FlatMapFunction<String, Tuple2<String, Integer>> {

        @Override
        public void flatMap(String value,
                Collector<Tuple2<String, Integer>> out) {
            // normalize and split the line
            String[] tokens = value.toLowerCase().split("\\W+");

            // emit the pairs
            for (String token : tokens) {
                if (token.length() > 0) {
                    out.collect(new Tuple2<String, Integer>(token, 1));
                }
            }
        }
    }
}

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