Java学生管理系统的操作与功能

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.io.StringReader;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.StringTokenizer;

/*
 * Created on 2005-1-11
 */

/**
 * @author 让炜
 * @since 1.0
 *
 * TODO 学生成绩管理系统
 * 通过学号查找,修改,删除数据
 * 
 */
public class LittleProgram 

{
    static boolean isDelete = true;
    static boolean isFind = true;
    public static void main(String [] args)//主方法,程序从这里开始运行  
    throws IOException,NumberNotFoundException
    {
        int choice=-1;
        do{
            LittleProgram lp = new LittleProgram();
            System.out.println();
            System.out.println("\t####################################");
            System.out.println();
            System.out.println("\t\t Java学生成绩管理系统1.1");
            System.out.println("\t\t请用学号查找,修改,删除数据");
            System.out.println();
            System.out.println("\t####################################\n");
            System.out.print("1.增加数据:\n"+
                    "2.查找数据:\n"+
                    "3.删除数据:\n"+
                    "4.清除所有数据:\n"+
                    "5.把数据全部打印到屏幕\n"+
                    "6.把成绩按学号排序\n"+
                    "7.修改数据\n"+
                    "8.统计已记录成绩学生数\n"+
                    "9.关于作者\n"+
                    "0.退出程序.\n" +
                    "输入:");
            BufferedReader in =                           //从终
                new BufferedReader(                       //端接
                        new InputStreamReader(System.in));//收数