資料

1949-10-01 14:21:02	34c
1949-10-01 19:21:02	38c
1949-10-02 14:01:02	36c
1950-01-01 11:21:02	32c
1950-10-01 12:21:02	37c
1951-12-01 12:21:02	23c
1950-10-02 12:21:02	41c
1950-10-03 12:21:02	27c
1951-07-01 12:21:02	45c
1951-07-02 12:21:02	46c
1951-07-03 12:21:03	47c

主程式

package com.zyd.tq;

import java.io.IOException;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
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;



public class TQRunner {
	public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {
		//1 獲取檔案系統
		Configuration conf = new Configuration();
		
		Job job = Job.getInstance(conf);
		
		job.setJarByClass(TQRunner.class);
		job.setJobName("TQ");
		//讀
		FileInputFormat.addInputPath(job, new Path(args[0]));
		FileOutputFormat.setOutputPath(job, new Path(args[1]));
		//map操作
		job.setMapperClass(TQMapper.class);
		//Reduce操作
		job.setReducerClass(TQReducer.class);
		//map的輸出的key和value都是Text
		job.setMapOutputKeyClass(Text.class);
		//如果key不對 啟動任務時候報unable to initialize any output collect
		job.setMapOutputValueClass(Text.class);
		job.waitForCompletion(true);
	}
}
 

map階段程式碼:

package com.zyd.tq;

import java.io.IOException;

import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;

/**
 * 
 * @author Administrator
 *傳入輸入的key value 輸入的key value
 *key 精確到年月 value是度數 是字串
 */

public class TQMapper extends Mapper<Object, Text, Text, Text>{

	
	@Override
	/**
	 * 重寫map方法
	 * 
	 */
	protected void map(Object key, Text value,
			Mapper<Object, Text, Text, Text>.Context context)
			throws IOException, InterruptedException {
		//時間和溫度是按製表符隔開的
		String[] split = value.toString().split("\t");
		//時間
		String time = split[0];
		//溫度
		String wd = split[1];
		
		context.write(new Text(time.substring(0,7)),new Text(wd));
		
	}

}
 

Reduce階段:

	package com.zyd.tq;
	
	import java.io.IOException;
	import java.util.ArrayList;
	import java.util.Collections;
	import java.util.Iterator;
	
	import org.apache.hadoop.io.Text;
	import org.apache.hadoop.mapreduce.Reducer;
	
	/**
	 * 
	 * @author Administrator
	 *根據map分割槽後 <text,text>
	 */
	public class TQReducer extends Reducer<Text, Text, Text, Text> {
	
		@Override
		/**
		 * 相同的key為一組
		 * 
		 * iterable是同一個月裡面所有的溫度,是所有的map直接拉過來以後的
		 */
		protected void reduce(Text key, Iterable<Text> iterable,
				Reducer<Text, Text, Text, Text>.Context context) throws IOException,
				InterruptedException {
			ArrayList<String> list = new ArrayList<String>();
			for(Text text : iterable){
				list.add(text.toString());
			}
			//按照字典排序
			Collections.sort(list);
			
			//得到最高的兩個溫度  即下標的最後兩個
			String maxWD = list.get(list.size()-1);
			String tmp = "";
			if (list.size()>=2) {
				String secondWD = list.get(list.size()-2);
				tmp = ":"+secondWD;
			}
			
			context.write(key,new Text(maxWD+tmp));
		}
	}