Hadoop MapReduce WordCount

WordCount.java

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
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.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

import java.io.IOException;

/**
 * Created by AhianZhang on 2018/5/11.
 */


public class WordCount
{

    public static class MyMapepr extends Mapper<LongWritable, Text, Text, LongWritable>
    {
        LongWritable one = new LongWritable(1);

        @Override
        protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException
        {
            //接收到每一行数据
            String line = value.toString();
            //按照指定分隔符进行拆分
            String[] words = line.split(" ");
            for (String word : words)
            {
                context.write(new Text(word), one);
            }
        }

    }

    public static class MyReducer extends Reducer<Text, LongWritable, Text, LongWritable>
    {

        @Override
        protected void reduce(Text key, Iterable<LongWritable> values, Context context) throws IOException, InterruptedException
        {
            long sum = 0;
            for (LongWritable value : values)
            {
                sum += value.get();
            }
            context.write(key, new LongWritable(sum));
        }
    }

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

        Configuration configuration = new Configuration();

        Path outputPath = new Path(args[1]);
        FileSystem fileSystem = FileSystem.get(configuration);
        if (fileSystem.exists(outputPath))
        {
            fileSystem.delete(outputPath, true);
            System.out.println("output file is already exitst but was deleted");
        }
        Job job = Job.getInstance(configuration, "wordcount");
        job.setJarByClass(WordCount.class);
        FileInputFormat.setInputPaths(job, new Path(args[0]));
        job.setMapperClass(MyMapepr.class);
        job.setMapOutputKeyClass(Text.class);
        job.setOutputValueClass(LongWritable.class);
        job.setReducerClass(MyReducer.class);
        job.setOutputKeyClass(Text.class);
        job.setMapOutputValueClass(LongWritable.class);
        FileOutputFormat.setOutputPath(job, new Path(args[1]));
        System.exit(job.waitForCompletion(true) ? 0 : 1);


    }
}