根据操作符加减乘除，判断并输出表达式ab的值

根据操作符加减乘除，判断并输出表达式ab的值

public static void main(String[] args) throws IOException{
        int a=100,b=6;
        char oper;
        System.out.println("请输入运算符（加减乘除）：");
        oper=(char)System.in.read();
        switch(oper){
            case '+':
                System.out.println(a+" "+oper+" "+b+" = "+(a+b));
                break;
            case '-':
                System.out.println(a+" "+oper+" "+b+" = "+(a-b));
                break;
            case '*':
                System.out.println(a+" "+oper+" "+b+" = "+(a*b));
                break;
            case '/':
                if(b==0){
                    System.out.println("被除数不能为0！");
                }else {
                    System.out.println(a+" "+oper+" "+b+" = "+(a*1.0/b));
                }
                break;
        }
    }


public class MathTest {
    public int sum(int a, int b) {
        return a + b;
    }

    public int sub(int a, int b) {
        return a - b;
    }

    public int multi(int a, int b) {
        return a * b;
    }

    public int div(int a, int b) throws Exception {
        if (b == 0) {
            throw new Exception("除数不能为0！");
        }
        return a / b;
    }

    public void menu() {
        System.out.println("菜单选项：");
        System.out.println("输入 1 开始操作.");
        System.out.println("输入 任意字符结束操作.");
    }

    public void result(int a, String op, int b) throws Exception {
        switch (op) {
            case "+":
                int sum = sum(a, b);
                System.out.println("a + b = " + sum);
                break;
            case "-":
                int sub = sub(a, b);
                System.out.println("a - b = " + sub);
                break;
            case "*":
                int multi = multi(a, b);
                System.out.println("a * b = " + multi);
                break;
            case "/":
                int div = div(a, b);
                System.out.println("a / b = " + div);
                break;
            default:
                System.out.println("操作符只能是+ — * /");

        }
    }

    public static void main(String[] args) throws Exception {
        MathTest mathTest = new MathTest();
        mathTest.menu();

        Scanner scanner = new Scanner(System.in);

        while (true) {
            String type = scanner.next();
            if ("1".equals(type)){
                System.out.println("请输入表达式，字符之间用空格隔开：a * b或a - b或a * b或a / b: 例如：3 * 4");
                int a = scanner.nextInt();
                String op = scanner.next();
                int b = scanner.nextInt();
                mathTest.result(a, op, b);
                System.out.println("输入1继续操作，输入其他字符结束");
            }else {
                break;
            }

        }
    }
}

img