mapreduce代码，需要注释解答

Question

mapreduce的代码，能不能来个厉害的弄个注释。要每步详细的注释，急

Answer 1

你这个是求每一个单词出现得个数

编写Mapper类
public class TokenizerMapper extends Mapper<Object,Text,Text,IntWritable>　{ 
　 @Override
    public void map(Object key, Text value, Context context) throws IOException, InterruptedException {
        String line = value.toString();//读取一行数据
        StringTokenizer st = new StringTokenizer(line);//使用空格分隔
        while (st.hasMoreTokens()) {
            String word = st.nextToken();//单词
            context.write(new Text(word), new IntWritable(1));//单词---> 1
        }
    }
}
编写Reducer类

public class IntSumReducer extends Reducer<Text, IntWritable, Text, IntWritable> {
    @Override
    public void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException {
        int sum = 0;//汇总
        for (IntWritable val : values) {
            sum += val.get();
        }
        context.write(key, new IntWritable(sum));//单词--->数量
    }
}

本地部署得运行代码
public class WordCount {
    public static void main(String[] args) throws Exception {
        Configuration cfg = new Configuration();//创建配置对象
        conf.set("mapreduce.framework.name","local");
        //本地模式运行mr,输入输出的数据可以在本地，也可以在hdfs
        //conf.set("fs.defaultFS","hdfs://hcmaster:9000");
        conf.set("fs.defaultFS","file:///");
        
        Job job = Job.getInstance(cfg, "word count");//创建job对象
        
        job.setJarByClass(WordCount.class);//创建运行job的类
        
        job.setMapperClass(TokenizerMapper.class);//设置mapper类
        job.setReducerClass(IntSumReducer.class); //设置Reduce类
        
        job.setOutputKeyClass(Text.class);//设置Reduce输出的key
        job.setOutputValueClass(IntWritable.class);//设置Reduce输出的value

        FileInputFormat.addInputPath(job, new Path(args[0]));//设置输入路径

        Path op1 = new Path(args[1]);
        FileSystem fs = FileSystem.get(cfg);

        if (fs.exists(op1)) {
            fs.delete(op1, true);
            System.out.println("存在此输出路径，已删除！！！");
        }

        FileOutputFormat.setOutputPath(job, op1);//设置输出路径
        boolean b = job.waitForCompletion(true); //提交job
        System.exit(b ? 0 : 1);
    }
}