<dependency>

        <groupId>jdk.tools</groupId>

        <artifactId>jdk.tools</artifactId>

        <version>1.6</version>

        <scope>system</scope>

        <systemPath>${JAVA_HOME}/lib/tools.jar</systemPath>

    </dependency>

    <dependency>

        <groupId>org.apache.hadoop</groupId>

        <artifactId>hadoop-hdfs</artifactId>

        <version>2.6.5</version>

    </dependency>

    <dependency>

        <groupId>org.apache.hadoop</groupId>

        <artifactId>hadoop-common</artifactId>

        <version>2.6.5</version>

    </dependency>

    <dependency>

        <groupId>org.apache.hadoop</groupId>

        <artifactId>hadoop-mapreduce-client-core</artifactId>

        <version>2.6.5</version>

    </dependency>

public class WordcountMapper extends Mapper<LongWritable,Text,Text,IntWritable>{

    @Override

    protected void map(LongWritable key, Text value, Context context)throws IOException, InterruptedException {

        String line = value.toString();

        for(String word : line.split(" ")) {

            context.write(new Text(word), new IntWritable(1));

        }

    }

}

public class WordcountReducer extends Reducer<Text, IntWritable,Text, IntWritable> {

    @Override

    protected void reduce(Text key, Iterable<IntWritable> values,Context context) throws IOException, InterruptedException {

        int count = 0;

        for(IntWritable value : values) {

            count += value.get();

        }

        context.write(key , new IntWritable(count));

    }

}

public class WordcountLancher {

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

        String inputPath = args[0];

        String outputPath = args[1];

        Job job = Job.getInstance();

        job.setMapperClass(WordcountMapper.class);

        job.setReducerClass(WordcountReducer.class);

        job.setMapOutputKeyClass(Text.class);

        job.setMapOutputValueClass(IntWritable.class);

        job.setOutputKeyClass(Text.class);

        job.setOutputValueClass(IntWritable.class);

        FileInputFormat.setInputPaths(job, new Path(inputPath));

        FileOutputFormat.setOutputPath(job, new Path(outputPath));

        boolean success = job.waitForCompletion(true);

        System.exit(success ? 0 : 1);

    }

}

hadoop fs -mkdir -p /wordcount/input

hadoop fs -put LICENSE.txt /wordcount/input

start-yarn.sh

 hadoop jar wordcount.jar me.huqiao.hadoop.mr.WordcountLancher /wordcount/input /wordcount/output

hadoop fs -cat /wordcount/output/part-r- |more