暂未解决的问题

计算程序

• scanner关闭后新建出现异常NoSuchElementException

import java.util.Scanner;

public class calculatorTest {
    public static void main(String[] args) {

        while(true) {//保证循环
            Scanner scanner = new Scanner(System.in);

            System.out.println("请输入第一个数");
            double a1 = scanner.nextDouble();//第二次运行到此处时报错，处理办法是删掉scanner.close（）

            System.out.println("请输入第二个数");
            double a2 = scanner.nextDouble();

            System.out.println("请输入运算符");

            String str = scanner.next();

                switch (str) {
                    case "+":
                        System.out.println(add(a1, a2));
                        break;
                    case "-":
                        System.out.println(subtraction(a1, a2));
                        break;
                    case "*":
                        System.out.println(multiplication(a1, a2));
                        break;
                    case "/":
                        System.out.println(division(a1, a2));
                        break;
                    default:
                        System.out.println("符号输入错误，请重新输入");
                }
            scanner.close();
        }

    }
    public static double add(double x,double y){//定义加法
        return x+y;
    }
    public static double subtraction(double x,double y){//定义减法
        return x-y;
    }
    public static double multiplication(double x,double y){//定义乘法
        return x*y;
    }
    public static double division(double x,double y){//定义除法
        return x/y;
    }
}