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下边是我的实现。  hawon1 的实现也是正确的，e69da5e6ba903231313335323631343130323136353331333332613761

我与它的不同是没有频繁的创建文件流的开消import java.io.BufferedReader;

import java.io.File;

import java.io.FileReader;

import java.io.FileWriter;

import java.util.ArrayList;

import java.util.HashMap;

import java.util.Iterator;

import java.util.List;

import java.util.Map;

public class Test {

public static void main(String[] args) {

File file = new File("id.txt");

Map<String, List<SaveIDFile>> map = new HashMap<String, List<SaveIDFile>>();

try {

FileReader fr = new FileReader(file);

BufferedReader br = new BufferedReader(fr);

br.readLine();// 标题行忽略

List<SaveIDFile> list = null;

while (br.ready()) {

String line = br.readLine();

SaveIDFile data = new SaveIDFile(line);

if (map.containsKey(data.id)) {

list = map.get(data.id);

} else {

list = new ArrayList<SaveIDFile>();

map.put(data.id, list);

}

list.add(data);

}

br.close();

fr.close();

Iterator<String> iterator = map.keySet().iterator();

while (iterator.hasNext()) {

String id = iterator.next();

FileWriter fw = new FileWriter(id + ".txt");

list = map.get(id);

SaveIDFile tmp = list.get(0);

fw.write(tmp.getTitle() + "\r\n");

for (int i = 0; i < list.size(); i++) {

tmp = list.get(i);

fw.write(tmp.toString() + "\r\n");

}

fw.close();

}

} catch (Exception e) {

}

}

}

class SaveIDFile {

String id = null;

String day = null;

String hour = null;

String count = null;

public SaveIDFile(String line) {

String[] array = line.split(",");

int index = 0;

id = array[index++];

day = array[index++];

hour = array[index++];

count = array[index++];

}

public String getTitle() {

return "id day hour count";

}

public String toString() {

return id + "," + day + "," + hour + "," + count + "";

}

}