java写一个简单的计算器 加减乘除1

public class HelloWord {
    public static void main(String[] args){
        //用scanner接收输入信息
        Scanner scanner = new Scanner(System.in);
        //接收多个信息 每一个以回车结束 
        System.out.println("输入第一个参数a");
        double a = scanner.nextDouble();
        System.out.println("输入运算符");
        String oper = scanner.next();
        System.out.println("输入第二个参数b");
        double b = scanner.nextDouble();
        //声明类对象 用来调用方法
        HelloWord helloWord = new HelloWord();
        //通过运算符判断加减乘除
        switch(oper){
            case "+":
                System.out.println("加法"+helloWord.add(a,b));
                //不要忘了break 否则顺序执行
                break;
            case "-":
                System.out.println("减法"+helloWord.sub(a,b));
                break;
            case "*":
                System.out.println("乘法"+helloWord.mult(a,b));
                break;
            case "/":
                System.out.println("除法"+helloWord.div(a,b));
                break;
        }




        }
//声明加减乘除的方法
    public static double add(double a,double b){
        return a + b;
    }
    public static double sub(double a,double b){
        return a - b;
    }
    public static double mult(double a,double b){
        return a * b;
    }
    public static double div(double a,double b){
        return a/b;
    }

}