java控制台版本的学生管理系统

用ArrayList实现的一个学生管理系统，有添加，删除，更改，查询全体学生信息四个功能，较为粗糙简陋

package studentManagementSystem;

import java.util.ArrayList;
import java.util.Scanner;

public class main
{
    public static void main(String[] args)
    {
        Scanner input=new Scanner(System.in);
        ArrayList<Student> arr=new ArrayList<>();
        while(true){
            System.out.println("请您输入你想使用的功能:");
            System.out.println("1.添加功能\n2.删除功能\n3.修改功能\n4.查询功能" );
            int choice=input.nextInt();
            switch (choice) {
            case 1:add(arr,input);break;
            case 2:delete(arr,input);break;
            case 3:change(arr,input);break;
            case 4:inquire(arr);break;
        }  }
    }

    public static void add(ArrayList<Student> arr,Scanner input)
    {

            System.out.println("请输入学生id：");
            long id=input.nextLong();

        for (int i = 0; i < arr.size(); i++)
        {
            if(arr==null)break;
            Student op=new Student();
            op=arr.get(i);
            if(op.getId()==id) {System.out.println("该学生已存在");return;}
        }
            System.out.println("请输入学生姓名：");
            String name=input.next();
            System.out.println("请输入学生年龄：");
            int age= input.nextInt();
            System.out.println("请输入学生家庭住址：");
            String address= input.next();
            Student s=new Student(id,name,age,address);
            arr.add(s);
            System.out.println("已经成功添加该学生！");
        }


    public static void delete(ArrayList<Student> arr,Scanner input)
    {
        if(arr.size()==0){
            System.out.println("暂无学生信息,请先添加学生信息");return;}
        System.out.println("请输入学生id：");
         long id= input.nextInt();
        Student s=new Student();
        int num;
         for (int i = 0; i < arr.size(); i++)
         {
          if(arr.get(i).getId()==id)
          {   s=arr.get(i);
              System.out.println("该学生信息：学号 "+s.getId()+" 姓名："+s.getName()+" 年龄："+s.getAge()+" 家庭住址："+s.getAddress());
              System.out.println("是否删除？\n1.是 2.否");
              int choice= input.nextInt();
              switch (choice) {
                  case 1:arr.remove(i);System.out.println("该学生已删除！");break;
                  case 2:System.out.println("该学生未删除！");break;
              }
              break;}
          else if(i== arr.size()-1&&s.getId()!=id){
              System.out.println("该学生不存在！");
          }
         }

    }

    public static void change(ArrayList<Student> arr,Scanner input)
    {
        if(arr.size()==0){
            System.out.println("暂无学生信息,请先添加学生信息");return;}
        System.out.println("请输入你想修改的学生的id：");
        long id= input.nextLong();
        for (int i = 0; i < arr.size(); i++)
        {
            Student s=arr.get(i);
            if(s.getId()==id)
            {
                System.out.println("请输入修改的学生姓名：");
                String name=input.next();
                System.out.println("请输入修改的学生年龄：");
                int age= input.nextInt();
                System.out.println("请输入修改的学生家庭住址：");
                String address= input.next();
                Student news=new Student(id,name,age,address);
                arr.set(i,news);
                System.out.println("修改成功！");break;
            }
            else if(i== arr.size()-1&&s.getId()!=id){
                System.out.println("该学生不存在！");
            }
        }
    }

    public static void inquire(ArrayList<Student> arr)
    {
        if(arr.size()==0){
            System.out.println("暂无学生信息,请先添加学生信息");return;}
        for (int i = 0; i < arr.size(); i++)
        {
        Student s=new Student();
        s=arr.get(i);
            System.out.println(s.getId()+" "+s.getName()+" "+s.getAge()+" "+s.getAddress());
            System.out.println("-----------------------------------------------------");
        }
    }


    }

public class Student
{
    private long id;
    private String name;
    private int age;
    private String address;
    public Student(){}
    public Student(long id, String name, int age, String address) {
        this.id = id;
        this.name = name;
        this.age = age;
        this.address = address;
    }

    public long getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }
}