java简易两数计算器

public class calculator {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int t = 1;

        while (t ==1) { //用来循环输入
            System.out.println("输入第一个数：");
            double n = scanner.nextDouble();
            System.out.println("输入符号");
            String v = scanner.next();
            System.out.println("输入第二个数");
            double m = scanner.nextDouble();

            switch (v) {
                case "+":
                    double c1 = add(n, m);
                    System.out.println(c1);
                    break;
                case "-":
                    double c2 = sub(n, m);
                    System.out.println(c2);
                    break;
                case "*":
                    double c3 = mul(n, m);
                    System.out.println(c3);
                    break;
                case "/":
                    if (m == 0) {
                        System.out.println("除数不能为0，请重新输入！");
                    } else {
                        double c4 = div(n, m);
                        System.out.println(c4);
                    }
                    break;
            }

            System.out.println("是否进行再次运算？输入YES或者NO");
            String str=scanner.next();
            if(str.equals("YES")){//①对于字符串类型来说，"=="运算符用于比较两个变量本身的值，即两个对象在内存中的首地址
                t=1;              //equals()方法则是比较两个字符串中所包含的内容是否相同
            }else{                //②对于非字符串类型的变量来说，"=="运算符和equals方法都用来比较两个对象在内存中的首地址
                t=0;
                scanner.close();
            }
        }
    }
    public static double add(double a,double b){
        double c=a+b;
        return c;
    }

    public static double sub(double a,double b){
        double c=a-b;
        return c;
    }
    public static double mul(double a,double b){
        double c=a*b;
        return c;
    }
    public static double div(double a,double b){
        double c=a+b;
        return c;
    }

}