1、定义个文档“员工.txt”，里面的内容为：
李文，北京
李希，北京
张小小，河南
王文，河北
董信，北京
张坤，北京
万三，江西
戴天，河南
庞大，湖北
彭克，浙江

生成另外一个文档“员工统计.txt”中，其格式为：
北京,4(董信,李文,李希,张坤)
河南,2(戴天,张小小)
河北,1(王文)
江西,1(万三)
湖北,1(庞大)
浙江,1(彭克)

使用类集方法

使用List接口

package chapter13;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;

public class Job {

    public static void main(String[] args) throws IOException  {
        // TODO Auto-generated method stub
        String file1 = "d:/员工.txt";
        File f1 = new File(file1);
        FileReader in = new FileReader(f1);
        BufferedReader breader = new BufferedReader(in);
        String aLine;
        ArrayList<String> listProvince = new ArrayList<String>();
        ArrayList<Integer> listNumber = new ArrayList<Integer>();
        ArrayList<String> listDetail = new ArrayList<String>();

        while ((aLine = breader.readLine()) !=  null)
        {
            String name = aLine.substring(0, aLine.indexOf("，"));        //取出从0到”，“变成子字符串
            String province = aLine.substring(aLine.indexOf("，" ) + 1);//取出”，“以后的所有子字符串
            int pos = 0;
            boolean find = false;
            for (int i = 0; i < listProvince.size(); i++)
            {
                if (province.equals(listProvince.get(i)))
                {
                    pos = i;
                    find = true;
                    break;
                }
            }
            if (find)
            {
                listNumber.set(pos, (int)listNumber.get(pos) + 1);
                listDetail.set(pos, listDetail.get(pos) + "," + name);
            }
            else
            {
                listProvince.add(province);
                listNumber.add(1);
                listDetail.add(name);
            }
        }
        breader.close();
        String file2 = "d:/员工统计.txt";
        File f2 = new File(file2);
        if(f2.exists())
            f2.delete();
        FileWriter writerStream = new FileWriter(file2);
        BufferedWriter bwriter = new BufferedWriter(writerStream);

        for(int i = 0; i < listProvince.size(); i++)
        {
            aLine = listProvince.get(i) + "," + listNumber.get(i) + "(" + listDetail.get(i) + ")\r\n";
            bwriter.write(aLine);
        }
        bwriter.flush();
        bwriter.close();
    }

}

使用Map接口

package chapter13;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

public class Job2 {

    public static void main(String[] args) throws IOException {
        // TODO Auto-generated method stub
        String file = "d:/员工.txt";
        FileReader in = new FileReader(file);
        BufferedReader breader = new BufferedReader(in);
        Map<String, String> map = new HashMap<String, String>();
        String aLine;
        while((aLine = breader.readLine()) != null)
        {
            String name = aLine.substring(0, aLine.indexOf("，"));
            String province = aLine.substring(aLine.indexOf("，") + 1);
            if(map.get(province) != null)
            {
                map.replace(province, map.get(province) + "，" + name);
            }
            else
                map.put(province, name);
            breader.close();
            Set<String> keys = map.keySet();
            Iterator<String> iter = keys.iterator();
            String file2 = "d:/员工统计.txt";
            File f = new File(file2);
            if(f.exists())
                f.delete();
            FileWriter writerStream = new FileWriter(file2);
            BufferedWriter bwriter = new BufferedWriter(writerStream);
            while(iter.hasNext())
            {
                String str = iter.next();
                String[] split = map.get(str).split(",");    //把一个字符串分隔成字符串数组，分隔符为”，“
                bwriter.write(str + "," + split.length + "(" + map.get(str) + ")\r\n");    //获取分隔数组长度
            }
            bwriter.flush();
            bwriter.close();
        }
    }

}

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