java简单系统

学生管理系统完整代码实现练习
代码示例：
import java.security.DrbgParameters.NextBytes;
import java.util.ArrayList;
import java.util.Scanner;
public class StudentSystem {
public static void main(String[] args) {
ArrayList list=new ArrayList();
loop: while(true) {
System.out.println("--------欢迎进入学生管理系统---------");
System.out.println("1:添加学生");
System.out.println("2:删除学生");
System.out.println("3:修改学生");
System.out.println("4:查询学生");
System.out.println("5:退出");
System.out.println("请输入您的选择：");
Scanner sc =new Scanner(System.in);
String choose=sc.next();
switch (choose) {
case "1" -> addStudent(list) ;
case "2" -> deleteStudent(list);
case "3" -> updateStudent(list);
case "4" -> queryStudent(list);
case "5" -> {
System.out.println("退出");
break loop;
}
default -> System.out.println("没有这个选项");
}
}
}
public static void addStudent(ArrayList list){
Student s=new Student();
Scanner sc=new Scanner(System.in);
String id=null;
while (true) {
System.out.println("请输入学生id");
id = sc.next();
Boolean flag=contains(list, id);
if(flag) {
System.out.println("该id已经存在，请重新输入");
}else {
s.setId(id);
break;
}
}
System.out.println("请输入学生姓名");
String name=sc.next();
s.setName(name);
System.out.println("请输入学生年龄");
int age=sc.nextInt();
s.setAge(age);
System.out.println("请输入学生家庭住址");
String address=sc.next();
s.setAddress(address);
list.add(s);
System.out.println("添加成功");
}

public static void deleteStudent(ArrayList<Student> list){
	System.out.println("请输入要删除的学生id");
	Scanner sc=new Scanner(System.in);
	String id=sc.next();
	int index=getIndex(list, id);
	if(index>=0) {
		list.remove(index);
		System.out.println("删除成功");
	}else {
		System.out.println("id不存在");
	}
}

public static void updateStudent(ArrayList<Student> list){
	System.out.println("请输入要修改学生的id");
	Scanner sc=new Scanner(System.in);
	String id=sc.next();
	int index=getIndex(list, id);
	if(index==-1) {
		System.out.println("要修改的id"+id+"不存在,请重新输入");
		return;
	}
	Student stu=list.get(index);
	
	System.out.println("请输入学生姓名");
	String newname=sc.next();
	stu.setName(newname);
	
	System.out.println("请输入学生年龄");
	int newage=sc.nextInt();
	stu.setAge(newage);
	
	System.out.println("请输入学生地址");
	String newaddress=sc.next();
	stu.setAddress(newaddress);
	
	System.out.println("修改成功");
}

public static void queryStudent(ArrayList<Student> list){
	if(list.size()==0) {
		System.out.println("当前无学生信息");
		return;
	}
	System.out.println("id\t\t姓名\t年龄\t家庭住址");
	for (int i = 0; i < list.size(); i++) {
		Student stu=list.get(i);
		System.out.println(stu.getId()+"\t"+stu.getName()+"\t"+stu.getAge()+"\t"+stu.getAddress());
	}
}
public static boolean contains(ArrayList<Student> list,String id) {
	for(int i=0;i<list.size();i++) {
		Student student=list.get(i);
		String sid=student.getId();
		if(sid.equals(id)) {
			return true;
		}
	}
	return false;
}
public static int getIndex(ArrayList<Student> list,String id) {
	for (int i = 0;i<list.size() ; i++) {
		Student stu=list.get(i);    //得到学生对象
		String sid=stu.getId();    //得到id
		if(sid.equals(id)) {    //进行比较
			return i;
		}
	}
	return -1;
}

}

javabean：
public class Student {
private String id;
private String name;
private int age;
private String address;

public Student(){
}

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

public String getId() {
	return id;
}

public void setId(String 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;
}

}