IntWritable数据类型

IntWritable是Hadoop中的一种数据类型，用于表示整数。它是Writable接口的实现类之一，可以在Hadoop的MapReduce程序中作为输入和输出的数据类型。

IntWritable类有两个主要的方法：get()和set()。get()方法返回IntWritable对象的值，而set()方法设置IntWritable对象的值。

下面是一个使用IntWritable作为MapReduce程序的输入和输出类型的示例：

public static class MyMapper extends Mapper<LongWritable, Text, Text, IntWritable> {
    private final static IntWritable one = new IntWritable(1);
    private Text word = new Text();

    public void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
        String line = value.toString();
        StringTokenizer tokenizer = new StringTokenizer(line);
        while (tokenizer.hasMoreTokens()) {
            word.set(tokenizer.nextToken());
            context.write(word, one);
        }
    }
}

public static class MyReducer extends Reducer<Text, IntWritable, Text, IntWritable> {
    private IntWritable result = new IntWritable();

    public void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException {
        int sum = 0;
        for (IntWritable val : values) {
            sum += val.get();
        }
        result.set(sum);
        context.write(key, result);
    }
}