编写完整的JAVA应用程序，求任意一个整形数和实型数的和、差、积与商？

import java.util.Scanner

public class Test {

public static void main(String[] args) {

Scanner sc = new Scanner(System.in)

int n = sc.nextInt()

while(n <100 || n >999){

System.out.println("对不起，您的输入有误，请重新输入一个三位数：")

n = sc.nextInt()

}

int a = n%10//a是个位数；

int b = (n%100)/10//b是十位数；

int c = n/100//c是百位数；

int sum = a + b + c

System.out.println("百位数是："+c+"\t十位数是："+b+"\t个位数是："+a)

System.out.println("各位相加之和是："+ sum)

}

}

public abstract class Shape {

public abstract double Area()

public abstract void printArea()

}

class Circle extends Shape {

int radius

public Circle(int radius) {

this.radius = radius

}

@Override

public double Area() {

return Math.pow(this.radius, 2) * Math.PI

}

@Override

public void printArea() {

// String.format("%.2f", Area()) 保留两位小数

System.out.println("半径为 " + this.radius + " 的圆的面积是 " + String.format("%.2f", Area()))

}

}

class Test {

public static void main(String[] args) {

// 生成一个 1 - 9 的随机整数

int radius = (int) (Math.random() * 9) + 1

// 创建一个 Circle 对象实例

Circle circle = new Circle(radius)

// 调用 printArea() 方法打印面积

circle.printArea()

}

}

public class User {

private String userName

private String password

private static int userNumber

public User(){

userNumber++

this.userName="unKnown"

this.password="123456"

}

public User(String userName){

userNumber++

this.userName=userName

this.password="123456"

}

public User(String userName,String password){

userNumber++

this.userName=userName

this.password=password

}

public void setPassword(String oldPassword,String newPassword){

if(this.password.equals(oldPassword)){

this.password=newPassword

System.out.println("Password set success")

}else{

System.out.println("Password set not success")

}

}

public String toString(){

return "UserName:"+this.userName+" Password:"+this.password

}

}

public class TestUser {

public static void main(String[] args){

User u=new User()

System.out.println(u)

System.out.println("请输入密码：")

Scanner s=new Scanner(System.in)

String old=s.nextLine()

System.out.println("请输入新的密码：")

String newp =s.nextLine()

u.setPassword(old, newp)

System.out.println(u)

}

}

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