，java文件读取，排序_J2SE

求救，java文件读取，排序
对input.txt文件中的学号进行冒泡排序，从小到大，文件是以逗号分隔的文件如
3110005837,张三,,计算机科学与技术10(1),,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
3110005838,李四,,计算机科学与技术10(1),,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,（大概有200行这样的数据）
排好后输出到output.txt
崩溃，做了好久都做不出，求打救

------解决方案--------------------------------------------------------

Java code

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.Arrays;public class Test {        BufferedReader br = null;    BufferedWriter bw = null;    static String [][] a = null;        public Test() throws IOException{        br = new BufferedReader(new FileReader(new File("c:"+File.separator+"exp.txt")));        bw = new BufferedWriter(new FileWriter(new File("f:"+File.separator+"1.txt")));    }        public void sort(){        String tmp[];        for(int i = 1;i < a.length;i++){            for(int j = 0;j < a.length - i;j++ ){                if(Integer.parseInt(a[j][0]) > Integer.parseInt(a[j+1][0])){                    tmp = a[j];                    a[j] = a[j+1];                    a[j+1] = tmp;                }            }        }    }        public void setArray() throws IOException{        String tmp = "";        for(int r = 0;r < a.length;r++){            for(int l = 0;l < a[r].length;l++){                if(l != a[r].length - 1){                    tmp = tmp + a[r][l] + ",";                }else{                    tmp = tmp + a[r][l] + "\r\n";                }            }            bw.write(tmp);            tmp = "";        }        bw.close();    }        public String[][] getArray() throws IOException{        String tmp[][] = new String[1024][1024];        int num = 0;        while(br.read() != -1){            tmp[num] = br.readLine().split(",");            num++;        }        tmp = Arrays.copyOf(tmp, num);        br.close();        return tmp;    }        public static void main(String[] args) throws IOException {        Test test = new Test();        a = test.getArray();        test.sort();        test.setArray();    }}
------解决方案--------------------------------------------------------
用Map试试
key为顺序值
value为一行值
------解决方案--------------------------------------------------------
如果学号等长，而且在行首，对整行排序即可。

Java code // jdk7List<String> conents = Files.readAllLine(path, Charset.defaultCharset());Collections.sort(contents);Files.write(path, contents, Charset.defaultCharset());