19、案例

案例

public class MethodDemo11 {
    public static void main(String[] args) {
        judge();
    }

    //加法
    public static double add(double x,double y) {
        return x + y;
    }

    //减法
    public static double sub(double x,double y) {
        return x - y;
    }

    public static double mul(double x,double y) {
        return x * y;
    }

    public static double div(double x,double y) {
        return x / y;
    }

    //判断是哪个方法
    public static void judge() {
        Scanner sc = new Scanner(System.in);
        System.out.println("请输入两个数：");
        double x = sc.nextDouble();
        double y = sc.nextDouble();
        System.out.println("请输入运算符（+,-,*,/）：");
        String operator = sc.next();
        double result = 0;

        switch ( operator ) {
            case "+":
                result = add(x,y);
                System.out.println(x + "+" + y + "=" + result);
                break;
            case "-":
                result = sub(x,y);
                System.out.println(x + "-" + y + "=" + result);
                break;
            case "*":
                result = mul(x,y);
                System.out.println(x + "*" + y + "=" + result);
                break;
            case "/":
                if ( y == 0 ) {
                    System.out.println("第二个数字不能为0，否则除法运算没有意义");
                } else {
                    result = div(x,y);
                    System.out.println(x + "*" + y + "=" + result);
                }
                break;
            default:
                System.out.println("你输入的是非法字符");
        }
    }
}

输入的不是四个运算符时

输入的是 + 时：

输入的是 - 时：

输入的是 * 时：

输入的是 / 时：

y 为 0时，输入的是 / 时：