用Java 类写出以上题目

好的，这是一个用 Java 写的计算器类的示例代码：

import java.util.Scanner;

public class Calculation {
    private double num1;
    private double num2;
    
    public Calculation(double num1, double num2) {
        this.num1 = num1;
        this.num2 = num2;
    }
    
    public double add() {
        return this.num1 + this.num2;
    }
    
    public double sub() {
        return this.num1 - this.num2;
    }
    
    public double times() {
        return this.num1 * this.num2;
    }
    
    public double div() {
        if (this.num2 == 0) {
            System.out.println("Error: division by zero");
            return 0;
        } else {
            return this.num1 / this.num2;
        }
    }
    
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter the first number: ");
        double num1 = sc.nextDouble();
        System.out.print("Enter the second number: ");
        double num2 = sc.nextDouble();
        Calculation calc = new Calculation(num1, num2);
        System.out.println("Addition: " + calc.add());
        System.out.println("Subtraction: " + calc.sub());
        System.out.println("Multiplication: " + calc.times());
        System.out.println("Division: " + calc.div());
        sc.close();
    }
}

你可以在控制台上输入两个数字，然后调用 `add()`、`sub()`、`times()`、`div()` 方法，分别进行加、减、乘、除的计算。