零钱通项目（Java实现-命令行练习版）

import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Scanner;
public class SmallChangeSys {
    public static void main(String[] args) {
        //定义变量并初始化
        boolean loop = true;
        String details = "=============================零钱通明细============================";
        double money = 0.0;
        double moneyin = 0.0;
        double moneyout = 0.0;
        String note = "null";
        Date date = null;
        Date date_out= null;
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm");//格式化时间格式
        do {
            System.out.println("=============================零钱通明细============================");
            System.out.println("\t\t\t\t\t\t1 零钱通明细");
            System.out.println("\t\t\t\t\t\t2 收益入账");
            System.out.println("\t\t\t\t\t\t3 消    费");
            System.out.println("\t\t\t\t\t\t4 退    出");
            System.out.println("请选择（1-4）：");
            Scanner sc = new Scanner(System.in);
            int i = sc.nextInt();
            switch (i){
                case 1 :
                    System.out.println("1 零钱通明细");
                    System.out.println(details);
                    break;
                case 2 :
                    System.out.println("2 收益入账");
                    Scanner in = new Scanner(System.in);
                    boolean flag = true;
                    while (flag){                           //对收益入账金额进行校验 >0
                        System.out.print("收益入账金额：");
                        moneyin = in.nextDouble();
                        if (moneyin <= 0){
                            System.out.println("收益入账金额必须大于0,请重新输入");
                            flag = true;
                        }else {
                            flag = false;
                        }
                    }
                    money = money +moneyin;
                    System.out.print("收益入账说明：");
                    note = in.next();
                    date = new Date();
                    details += "\n收益入账    \t+" + moneyin + "\t时间：" + sdf.format(date) + "\t余额：" + money + "\t说明：" + note;
                    break;
                case 3 :
                    System.out.println("3 消    费");
                    Scanner out = new Scanner(System.in);
                    boolean flag_out = true;
                    while (flag_out){                           //对消费金额进行校验 小于余额
                        System.out.print("消费金额：");
                        moneyout = out.nextDouble();
                        if (moneyout > money){
                            System.out.println("消费金额大于余额("+money+"),请重新消费");
                            flag_out = true;
                        }else {
                            flag_out = false;
                        }
                    }
                    money = money - moneyout;
                    System.out.print("消费说明：");
                    note = out.next();
                    date_out = new Date();
                    System.out.print("消费金额：");
                    details += "\n消    费\t-" + moneyout + "\t时间：" + sdf.format(date_out) + "\t余额：" + money+ "\t说明：" + note;
                    break;
                case 4 :
                    System.out.println("4 退出");
                    String exit_loop = null;
                    while (true){                           //退出确认，并校验输入是否有效
                        System.out.println("是否确认退出，y/n");
                        Scanner exit = new Scanner(System.in);
                        exit_loop = exit.next();
                        if ("y".equals(exit_loop) || "n".equals(exit_loop)){
                            break;
                        } else {
                            System.out.println("输入有误，请重新输入");
                        }
                    }
                    if (exit_loop.equals("y") ){
                        loop = false;
                    }else {
                        loop = true;
                    }
                    break;
                default:
                    System.out.println("菜单选择有误，请重新输入（1-4）");
            }
        }while(loop);
        System.out.println("零钱通已退出");
    }
}