MapReduce Hadoop Java

WordCountJob.java

import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.TextInputFormat;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;

import java.io.IOException;
import java.util.StringTokenizer;


public class WordCountJob extends Configured implements Tool {

    static public class WordCountMapper extends Mapper<LongWritable, Text, Text, IntWritable> {
        private final static IntWritable one = new IntWritable(1);
        private final Text text = new Text();

        @Override
        protected void map(LongWritable key, Text value, Context context)
                throws IOException, InterruptedException {
            StringTokenizer tokenizer = new StringTokenizer(value.toString());
            while (tokenizer.hasMoreTokens()) {
                text.set(tokenizer.nextToken());
                context.write(text, one);
            }
        }
    }

    static public class WordCountReducer
            extends Reducer<Text, IntWritable, Text, IntWritable> {
        @Override
        protected void reduce(Text key, Iterable<IntWritable> values, Context context)
                throws IOException, InterruptedException {
            int sum = 0;
            for (IntWritable value : values) {
                sum += value.get();
            }
            context.write(key, new IntWritable(sum));
        }
    }

    @Override
    public int run(String[] args) throws Exception {
        Job job = Job.getInstance(getConf(), "WordCount");
        job.setJarByClass(getClass());
        TextInputFormat.addInputPath(job, new Path(args[0]));
        job.setInputFormatClass(TextInputFormat.class);
        job.setMapperClass(WordCountMapper.class);
        job.setReducerClass(WordCountReducer.class);
        job.setCombinerClass(WordCountReducer.class);
        TextOutputFormat.setOutputPath(job, new Path(args[1]));
        job.setOutputFormatClass(TextOutputFormat.class);
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(IntWritable.class);
        return job.waitForCompletion(true) ? 0 : 1;
    }

    public static void main(String[] args) throws Exception {
        int exitCode = ToolRunner.run(
                new WordCountJob(), args);
        System.exit(exitCode);
    }
}