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代码：

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;/*** Created with IntelliJ IDEA.** @Author:* @Date* @Description:*/
public class student {private int number;private int age;private  String name;private  String address;public int getNumber () {return number;}public void setNumber (int number) {this.number = number;}public int getAge () {return age;}public void setAge (int age) {this.age = age;}public String getName () {return name;}public void setName (String name) {this.name = name;}public String getAddress () {return address;}public void setAddress (String address) {this.address = address;}public student (int number, int age, String name, String address) {this.number = number;this.age = age;this.name = name;this.address = address;}@Overridepublic String toString () {return "student{" +"number=" + number +", age=" + age +", name='" + name + '\'' +", address='" + address + '\'' +'}';}public static void main (String[] args) {//符合list的要求 这里用到了泛型，将类型参数化List<student> list=new ArrayList<> ();//初始化一个list.add (new student (1, 25, "张嘉文","广西南宁"));System.out.println ("学生管理系统 "+"你想干什么？请输入");System.out.println ("1:查询");System.out.println ("2:添加");System.out.println ("3:修改");System.out.println ("4:删除");System.out.println ("5:退出");Scanner login=new Scanner (System.in);while (true) {int choice = login.nextInt ();Scanner scanner = new Scanner (System.in);switch (choice) {case 1: {/*** 查询*/System.out.println ("查询信息");//foe each在这里体现for (student s : list) {System.out.println (s.toString ());}break;}case 2: {/*** 增加*/System.out.println ("请依次输入学号、姓名、年龄、住址。一行内输入、空格隔开");String add[] = scanner.nextLine ().split (" ");int addnum = Integer.parseInt (add[0]);for (student s : list) {if (addnum == s.getNumber ()) {System.out.println ("学号重复，添加失败");break;}}//int number, int age, String name, String addresslist.add (new student (addnum, Integer.parseInt (add[2]), add[1], add[3]));System.out.println ("添加成功");break;}case 3: {/*** 修改*/System.out.println ("请依次输入要修改人的学号、姓名、年龄、住址。一行内输入、空格隔开");String update[] = scanner.nextLine ().split (" ");int upnum=Integer.parseInt (update[0]);int updateIndex=0;for (student s : list) {if (upnum == s.getNumber ()) {//找到了，需要修改list.get (updateIndex).setName ( (update[1]));list.get (updateIndex).setAge (Integer.parseInt (update[2]));list.get (updateIndex).setNumber (upnum);list.get (updateIndex).setAddress (update[3]);System.out.println ("修改完毕");break;}updateIndex++;}}case  4:{/*** 删除*/System.out.println ("请依次输入要删除人的学号、姓名、年龄、住址。一行内输入、空格隔开");String update[] = scanner.nextLine ().split (" ");int denum=Integer.parseInt (update[0]);int deinex=0;for (student s : list) {if (denum == s.getNumber ()) {list.remove (deinex);}deinex++;}}case  5:{System.exit (1);}}}}
}