（2）新建一个包，名字为com.yarn。

（3）在这个包下创建类WordCountDriver并实现Tool接口：

package com.example.mapreduce;
import org.apache.hadoop.conf.Configuration;
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.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;

import java.io.IOException;
import java.util.Arrays;

//mapreduce: 分布式计算框架
// 提交任务给hadoop集群执行
// 它要做7件事 hadoop jar mc8.js com.example.mapreduce.WordCountDriver /要处理的文件夹 /结果路径
public class WordCountDriverTool implements Tool {
    private Configuration conf;
    public static void main(String[] args) throws Exception {
        switch(args[0]) {
            case "wordcount":
                int run = ToolRunner.run(new Configuration(), new WordCountDriverTool(), Arrays.copyOfRange(args,1, args.length));
                System.exit(run);
                break;
            default:
                throw new RuntimeException("no such tool" +args[0]);
        }
    }

    @Override
    public int run(String[] args) throws Exception {

        // 连接到hadoop集群
        // conf.set("fs.defaultFS", "hdfs://hadoop100:8020");
        Job job = Job.getInstance(conf);
        // 2. 关联本地的jar包
        job.setJarByClass(WordCountDriverTool.class);
        // 3. 关联Mapper和Reducer
        job.setMapperClass(WordCountMapper.class);
        job.setReducerClass(WordCountReducer.class);
        // 4. 设置Map的键值对泛型
        job.setMapOutputKeyClass(Text.class);
        job.setMapOutputValueClass(LongWritable.class);
        // 5. 设置Reduce的键值对泛型
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(LongWritable.class);

        // 6. 设置输入路径（D:\vm\wcinput）和输出路径（D:\vm\output01）
        FileInputFormat.setInputPaths(job, new Path(args[0]));
        FileOutputFormat.setOutputPath(job, new Path(args[1]));
        // 7. 提交job,根据返回值设置程序退出code
        return job.waitForCompletion(true) ? 0 : 1;
    }
    @Override
    public void setConf(Configuration configuration) {
        this.conf = configuration;
    }

    @Override
    public Configuration getConf() {
        return conf;
    }
}