跟着狂神学java，p50计算器实现源码，仅代表个人，不足之处，欢迎指正，谢谢

package com.kuang.Method;

import java.util.Scanner;

public class Demo08 {
    public static void main(String[] args) {
        String start = "s";
        String end = "e";
        String str = "0";
        String operator = "0";
        double result = 0;
        Scanner scanner = new Scanner(System.in);
        while (true){
            System.out.println("输入s以开始计算，或输入e以结束计算:");
            str = scanner.next();
            if (str.equals(start)){
                double num1 = 0;
                double num2 = 0;
                System.out.println("请输入num1：");
                num1 = scanner.nextDouble();

                do {
                    System.out.println("请输入要继续的指令：+、-、*、/、%、clr、e");
                    operator = scanner.next();
                    if ((operator.equals("+")) || (operator.equals("-")) || (operator.equals("*"))
                            || (operator.equals("/")) || (operator.equals("%")))
                    {
                        System.out.println("请输入num2：");
                        num2 = scanner.nextDouble();
                        switch (operator){
                            case "+":
                                result = add(num1,num2);
                                break;
                            case "-":
                                result = sub(num1,num2);
                                break;
                            case "*":
                                result = mul(num1,num2);
                                break;
                            case "/":
                                result = div(num1,num2);
                                break;
                            case "%":
                                result = mod(num1,num2);
                                break;
                        }
                        System.out.println("运算结果为："+num1+operator+num2+" = "+result);
                        System.out.println("====================================");
                        num1 = result;
                    }else if (operator.equals("clr")){
                        result = 0;
                        System.out.println("清零："+"result" +" = "+result);
                        System.out.println("====================================");
                        System.out.println("继续请输入s，结束请输入任意");
                        if (scanner.next().equals("s")){
                            System.out.println("请输入num1：");
                            num1 = scanner.nextDouble();
                        }else {
                            System.out.println("计算结束");
                            System.out.println("====================================");
                            break;
                        }
                    }else if (operator.equals("e"))
                    {
                        System.out.println("计算结束");
                        System.out.println("====================================");
                        // scanner.close();不能写这里，会导致：：：
                        // 直接break只是跳出当前do while循环，回到while循环
                        // 所以会回到System.out.println("输入s以开始计算，或输入e以结束计算:");
                        //由于scanner关闭，而又有str = scanner.next();导致错误
                        break;
                    }else {
                        System.out.println("您输入的运算符非预期");
                    }
                }while (true);

            }else if (str.equals(end)){
                scanner.close();
                System.out.println("计算结束");
                System.out.println("====================================");
                break;
            }else {
                System.out.println("输入指令非s或e，请重新输入。");
                System.out.println("------------------------------------");
                System.out.println("");
            }
        }
    }

    public static double add(double num1,double num2){
        double addSum = num1 + num2;
        return addSum;
    }
    public static double sub(double num1,double num2){
        double subSum = num1 - num2;
        return subSum;
    }
    public static double mul(double num1,double num2){
        double mulSum = num1 * num2;
        return mulSum;
    }
    public static double div(double num1,double num2){
        double divSum = num1 / num2;
        return divSum;
    }
    public static double mod(double num1,double num2){
        double modSum = num1 % num2;
        return modSum;
    }
}

标签：java,num1,num2,double,System,源码,println,p50,out
来源： https://www.cnblogs.com/LND-tingyu/p/16092914.html