java学生信息管理Arraylist的运用

import java.io.File;
import java.io.FileNotFoundException;
import java.io.PrintStream;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.Scanner;
 
public class Windzly {
    
    static ArrayList<Student> list = new ArrayList<Student>();
    
    public static void main(String[] arg) throws FileNotFoundException {
        Scanner sc = new Scanner(System.in);
        
        readfile();//读取文本文件
        
        
        int n;
        while(true)
        {
            System.out.println("1、添加学生    2、删除指定学号的学生    3、修改指定学号的成绩   "
                    + " 4、查找指定学号的信息    5、打印所有的学生信息    6、退出");
            n = sc.nextInt();
            if(n == 1)
            {
                addstudent();//添加学生；
            }
            else if(n == 2)
            {
                erasestudent();//删除指定学号的学生
                    
            }
            else if(n == 3)
            {
                editstudent();//修改指定学号的成绩
            }
            else if(n == 4)
            {
                findstudent();//查找学生信息
            }
            else if(n == 5)
            {
                printstudent();//打印所有学生的信息
            }
            else if(n == 6)
            {
                savestudent();
                System.exit(0);
                break;
            }
        }
    }

    public static void savestudent() throws FileNotFoundException {
        PrintStream put = System.out;
        System.setOut(new PrintStream(new File("y.txt")));
        Iterator it = list.iterator();
        while(it.hasNext())
        {
            Object object = it.next();
            System.out.println(object);
        }
        System.setOut(put);
    }

    public static void readfile() throws FileNotFoundException {
        Scanner sc = new Scanner(new File("s.txt"));
        while(sc.hasNext())
        {
            String s = sc.nextLine();
            String []ss = s.split(" ");
            Student student = new Student(ss[0],ss[1],ss[2]);
            list.add(student);
        }
    }

    public static void printstudent() {
        for(int i = 0; i < list.size(); i ++)
        {
            System.out.println(list.get(i).toString());
        }
    }

    public static void findstudent() {
        String s;
        Scanner sc = new Scanner(System.in);
        System.out.println("请输入学号");
        s = sc.nextLine();
        for(int i = 0; i < list.size(); i ++)
        {
            if(list.get(i).getNo().equals(s))
            {
                System.out.println(list.get(i).toString());
            }
        }
    }

    public static void editstudent() {
        String s,sco;
        Scanner sc = new Scanner(System.in);;
        System.out.println("请输入学号");
        s = sc.nextLine();
        for(int i = 0; i < list.size(); i ++)
        {
            if(list.get(i).getNo().equals(s))
            {
                System.out.println("请输入修改后的成绩");
                sco = sc.nextLine();
                list.get(i).setScore(sco);
            }
        }
    }

    public static void erasestudent() {
        Scanner sc = new Scanner(System.in);
        String s;
        System.out.println("请输入指定的学号");
        s = sc.nextLine();
        for(int i = 0; i < list.size(); i ++)
        {
            if(list.get(i).getNo().equals(s))
            {
                list.remove(i);
            }
        }
    }

    public static void addstudent() {
        String s; 
        Scanner sc = new Scanner(System.in);
        System.out.println("输出新同学的学号，姓名，成绩");
        s = sc.nextLine();
        String [] ss = s.split(" ");
        Student student = new Student(ss[0],ss[1],ss[2]);
        list.add(student);
    }
}

class Student
{
    String no;
    String name;
    String score;
    public Student() {
        super();
    }
    public Student(String no, String name, String score) {
        super();
        this.no = no;
        this.name = name;
        this.score = score;
    }
    @Override
    public String toString() {
        return "Student [学号：" + no + ", 姓名：" + name + ", 成绩：" + score
                + "]";
    }
    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((name == null) ? 0 : name.hashCode());
        result = prime * result + ((no == null) ? 0 : no.hashCode());
        result = prime * result + ((score == null) ? 0 : score.hashCode());
        return result;
    }
    public String getNo() {
        return no;
    }
    public void setNo(String no) {
        this.no = no;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getScore() {
        return score;
    }
    public void setScore(String score) {
        this.score = score;
    }
    
}