package org.example;

import org.apache.hadoop.io.IntWritable;

import org.apache.hadoop.io.LongWritable;

import org.apache.hadoop.io.Text;

import org.apache.hadoop.mapreduce.Mapper;

import java.io.IOException;

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

    @Override

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

        System.out.println(key);

        String line=value.toString();

        String[] words=line.split(" ");

        for(String word : words){

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

        }

    }

}

package org.example;

import org.apache.hadoop.io.IntWritable;

import org.apache.hadoop.io.Text;

import org.apache.hadoop.mapreduce.Reducer;

import java.io.IOException;

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

    @Override

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

        int total=0;

        for(IntWritable value : values){

            total+=value.get();

        }

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

    }

}

package org.example;

import org.apache.hadoop.conf.Configuration;

import org.apache.hadoop.fs.Path;

import org.apache.hadoop.io.IntWritable;

import org.apache.hadoop.io.Text;

import org.apache.hadoop.mapreduce.Job;

import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;

import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

import java.io.IOException;

public class WordCountMain {

    public static void main(String[] args) throws IOException, InterruptedException, ClassNotFoundException {

        //1. 建立连接

        Configuration cfg=new Configuration();

        Job job=Job.getInstance(cfg,"wc");

        job.setJarByClass(WordCountMain.class);

        //2. 指定 mapper 和 reduce

        job.setMapperClass(WordCountMapper.class);

        job.setReducerClass(WordCountReduce.class);

        // 指定 mapper 输出类型

        job.setMapOutputKeyClass(Text.class);

        job.setMapOutputValueClass(IntWritable.class);

        // 指定 reduce 输出类型

        job.setOutputKeyClass(Text.class);

        job.setMapOutputValueClass(IntWritable.class);

        // 指定输出路径

        FileInputFormat.setInputPaths(job,new Path("S:/test/data.txt"));

        FileOutputFormat.setOutputPath(job,new Path("S:/test/M"));

        //3. 运行

        boolean result=job.waitForCompletion(true);

        System.out.println(result?"成功":"失败");

        System.exit(result?0:1);

    }

}