大话设计模式--第一章 简单工厂设计模式

package com.chapter1;

public class Caculator1 {
    public static void main(String[] args) {
        if(args.length < 3){
            System.out.println("参数个数异常");
            return ;
        }
        Double num1 = Double.parseDouble(args[0]);
        Double num2 = Double.parseDouble(args[1]);
        String operator = args[2];
        Double total = 0d;
        switch(operator){
        case "+":
            total = num1 + num2;
            break;
        case "-":
            total = num1 - num2;
            break;
        case "*":
            total = num1 * num2;
            break;
        case "/":
            if("0".equals(num2) || num2 == 0){
                System.out.println("除数不能是0");
                return ;
            }
            total = num1 / num2;
            break;
        }
        System.out.println(total);
    }
}