java-编写一个计算器and交换实参的值

1. 编写一个calculator，有两个属num1，num2，这两个数据的值不能再定义的同时初始化，最后实现加减乘除。

//计算器
class Calculator {
    private int num1;
    private int num2;

    public void setNum1(int num1) {
        this.num1 = num1;
    }

    public void setNum2(int num2) {
        this.num2 = num2;
    }

    public int add(){
        return this.num1 + this.num2;
    }

    public int sub(){
        return this.num1 - this.num2;
    }

    public int mul(){
        return this.num1 * this.num2;
    }

    public double dec(){
        return this.num1*1.0 / this.num2;
    }

    public static void main(String[] args) {
        Calculator calculator = new Calculator();
        calculator.setNum1(10);
        calculator.setNum2(20);
        System.out.println("加法");
        System.out.println(calculator.add());
        System.out.println("除法");
        System.out.println(calculator.dec());
    }
}

 2.实现交换两个变量的值（交换实参的值）

//交换实参的值
class Myvalue {
    public int val;
}
public class TestDemo {
    public static void swap(Myvalue myval1, Myvalue myval2) {
        int tmp = myval1.val;
        myval1.val =  myval2.val;
        myval2.val = tmp;
    }

    public static void main(String[] args) {
        Myvalue myvalue1 = new Myvalue();
        myvalue1.val = 10;
        Myvalue myvalue2 = new Myvalue();
        myvalue2.val = 20;
        System.out.println(myvalue1.val);
        System.out.println(myvalue2.val);
        System.out.println("交换得");
        swap(myvalue1, myvalue2);
        System.out.println(myvalue1.val);
        System.out.println(myvalue2.val);
    }
}