小项目--零钱通

package 项目.零钱通;

import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Scanner;

public class SmallChang01 {
    //化繁为简（显示菜单，选择菜单，提示信息）

    public static void main(String[] args) {
        boolean loop = true;

        Scanner scanner = new Scanner(System.in);
        String key = "";
        String detials = "---------零钱通明细---------";
        double money = 0;
        double banlance = 0;
        Date date = null;
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd  HH:mm");//日期格式化
        String note = "";

        do {//用do-while循环是因为要至少显示一次
            System.out.println("n--------菜单----------");
            System.out.println("ttt1  零钱通明细");
            System.out.println("ttt2  收益入账");
            System.out.println("ttt3  消费");
            System.out.println("ttt4  退     出");

            System.out.print("请选择（1-4）：");
            key = scanner.next();

            //用switch分支结构
            switch (key){
                case "1":
                    System.out.println(detials);
                    break;
                case "2":
                    System.out.print("收益入账金额：");
                    money = scanner.nextDouble();
                    banlance += money;
                    //金额的合理性判断（找出不正确的条件）
                    if (money<=0){
                        System.out.println("您输入的金额有问题");
                        break;
                    }

                    //拼接收益入账信息
                    date = new Date();//获取当前日期
                    detials += "n收益入账t+"+money+"t"+sdf.format(date)+"t"+banlance;
                    break;
                case "3":
                    System.out.print("请输入您的消费金额：");
                    money = scanner.nextDouble();
                    if (money <= 0 || money>banlance){//不能小于零也不能比入账的金额多
                        System.out.println("您的消费金额应该在0- "+banlance);
                    }

                    System.out.print("消费说明：");
                    note = scanner.next();
                    banlance -= money;

                    //拼接消费信息
                    date = new Date();//获取当前日期
                    detials += "n"+note+"t-"+money+"t"+sdf.format(date)+"t"+banlance;

                    break;
                case "4":
                    String choice = "";
                    while(true){
                        System.out.println("您确定要退出？ y/n");
                        choice = scanner.next();

                        if("y".equals(choice) || "n".equals(choice)){//输入结果是y或n循环才结束
                            break;
                        }
                    }

                    if ("y".equals(choice)){
                        loop = false;
                    }else if ("n".equals(choice)){
                        loop = true;
                    }
                    break;
                default:
                    System.out.println("选择有问题");
            }
        }while (loop);

        System.out.println("-------退出了零钱通项目---------");
    }
}

改用面向对象写法（OOP）：

package 项目.零钱通;

import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Scanner;

//使用面向对象的知识完成零钱通项目
public class SmallChang02 {
    public static void main(String[] args) {
//        SmallChangOOP oop = new SmallChangOOP();
//        oop.mainMenu();

        new SmallChangOOP().mainMenu();//匿名对象
    }
}
class SmallChangOOP{
    //属性
    boolean loop = true;

    Scanner scanner = new Scanner(System.in);
    String key = "";
    String detials = "---------零钱通明细---------";
    double money = 0;
    double banlance = 0;
    Date date = null;
    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd  HH:mm");//日期格式化
    String note = "";


    //将零钱通的各个功能封装成一个方法

    public void mainMenu(){
        do {//用do-while循环是因为要至少显示一次
            System.out.println("n--------菜单----------");
            System.out.println("ttt1  零钱通明细");
            System.out.println("ttt2  收益入账");
            System.out.println("ttt3  消费");
            System.out.println("ttt4  退     出");

            System.out.print("请选择（1-4）：");
            key = scanner.next();

            //用switch分支结构
            switch (key){
                case "1":
                    this.detial();
                    break;
                case "2":
                    this.income();
                    break;
                case "3":
                    this.pay();
                    break;
                case "4":
                    this.exit();
                    break;
                default:
                    System.out.println("选择有问题");
            }
        }while (loop);
        System.out.println("您退出了可爱的零钱通");
    }

    //详细信息
    public void detial(){
        System.out.println(detials);
    }

    //入账
    public void income(){
        System.out.print("收益入账金额：");
        money = scanner.nextDouble();
        banlance += money;
        //金额的合理性判断（找出不正确的条件）
        if (money<=0){
            System.out.println("您输入的金额有问题");
            return;//退出执行该方法
        }

        //拼接收益入账信息
        date = new Date();//获取当前日期
        detials += "n收益入账t+"+money+"t"+sdf.format(date)+"t"+banlance;
    }

    //消费
    public void pay(){
        System.out.print("请输入您的消费金额：");
        money = scanner.nextDouble();
        if (money <= 0 || money>banlance){//不能小于零也不能比入账的金额多
            System.out.println("您的消费金额应该在0- "+banlance);
            return;
        }

        System.out.print("消费说明：");
        note = scanner.next();
        banlance -= money;

        //拼接消费信息
        date = new Date();//获取当前日期
        detials += "n"+note+"t-"+money+"t"+sdf.format(date)+"t"+banlance;
    }

    //退出
    public void exit(){
        String choice = "";
        while(true){
            System.out.println("您确定要退出？ y/n");
            choice = scanner.next();

            if("y".equals(choice) || "n".equals(choice)){//输入结果是y或n循环才结束
                break;
            }
        }

        if ("y".equals(choice)){
            loop = false;
        }else if ("n".equals(choice)){
            loop = true;
        }
    }
}