用Java打造简易计算器的实现步骤

public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        System.out.println("请输入第一个数字：");
        double num1=sc.nextDouble();
        System.out.println("请输入计算符（+，—，*，/）：");
        String op=sc.next();
        System.out.println("请输入第二个数字：");
   
         }

public class Demo101 {
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        System.out.println("请输入第一个数字：");
        double num1=sc.nextDouble();
        System.out.println("请输入计算符（+，—，*，/）：");
        String op=sc.next();
        System.out.println("请输入第二个数字：");
        double num2=sc.nextDouble();
        double result=calc(num1,op,num2);
        System.out.println(num2+" "+op+" "+num2+" = "+result);
    }

    public static double calc(double num1, String op, double num2) {
        double result=0;
        switch (op){
            case "+":
                result=num1+num2;
                break;
            case "-":
                result=num1-num2;
                break;
            case "*":
                result=num1*num2;
                break;
            case "/":
                result=num1/num2;
                break;
            default:
                System.out.println("请输入有效运算符");
        }
        return result;
    }