模拟两数相加

模拟两数相加

//键入两数,让其相加
public class Demo3 {
    public static void main(String[] args) {
        System.out.println("这是一个计算器测试");
        System.out.println("请输入你要做的运算:+,-,*,/");
        Scanner scanner = new Scanner(System.in);
        String i = "";
        if(scanner.hasNextLine()){
            i = scanner.nextLine();
        }
        switch (i){
            case "+" :
                System.out.print("请输入第一个加数数:");
                double add1 = getNum(scanner);
                System.out.print("请输入第二个加数数:");
                double add2 = getNum(scanner);
                add(add1,add2);
                break;
            case "-" :
                break;
            default:
                break;

        }
        scanner.close();
    }
    public static void add(double i,double j){
        double result = i+j;
        System.out.println(i + "+" + j + "=" + result);
    }
    public static double getNum(Scanner scanner){
        double result = 0;
        while(true){
            if(scanner.hasNextDouble()){
                result = scanner.nextDouble();
                return result;
            }else {
                //获取下一个输入值,否则循环会一直判断当前输入值,陷入死循环
                System.out.println("请输入一个数");
                scanner.nextLine();
            }
        }
    }
}