把單詞按照ASCII碼奇偶分區(qū)（Partitioner）

1、分析

2、自定義分區(qū)

import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Partitioner;

public class WordCountPartitioner extends Partitioner<Text, IntWritable>{

    @Override
    public int getPartition(Text key, IntWritable value, int numPartitions) {
        
        // 1 獲取單詞key  
        String firWord = key.toString().substring(0, 1);
        char[] charArray = firWord.toCharArray();
        int result = charArray[0];
        // int result  = key.toString().charAt(0);

        // 2 根據(jù)奇數(shù)偶數(shù)分區(qū)
        if (result % 2 == 0) {
            return 0;
        }else {
            return 1;
        }
    }
}

3、在驅(qū)動(dòng)中配置加載分區(qū)，設(shè)置reducetask個(gè)數(shù)

job.setPartitionerClass(WordCountPartitioner.class);
job.setNumReduceTasks(2);

4、基于wordcount案例

http://www.itdecent.cn/p/c8726f1ccd8f

5、Code -> GitHub

https://github.com/liufengji/hadoop_mapreduce.git