自己写的第一个java项目！

项目名为“零钱通”

细节参考：

【零基础 快速学Java】韩顺平 零基础30天学会Java

基本版：

  1 package project;
  2 
  3 import java.text.SimpleDateFormat;
  4 import java.util.Date;
  5 import java.util.Scanner;
  6 
  7 public class SmallChangeSys {
  8     public static void main(String[] args) {
  9         //1.零钱通菜单
 10         boolean loop = true;
 11         Scanner scanner = new Scanner(System.in);
 12         String key = "";
 13         //2.零钱通明细
 14         String details = "==============零钱通明细==============";
 15         //3.收益入账
 16         double money = 0;
 17         double balance = 0;
 18         Date date = null;
 19         SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm");//用于日期格式化的
 20         //4.零钱通消费
 21         String note = "";
 22         //5.零钱通退出确认
 23         String choice = "";
 24         //6.判断金额入账和消费时金额是否合理
 25 
 26         do {
 27             System.out.println("==============零钱通菜单==============");
 28             System.out.println("			1 零钱通明细");
 29             System.out.println("			2 收益入账");
 30             System.out.println("			3 消费");
 31             System.out.println("			4 退    出");
 32 
 33             System.out.println("请选择1-4");
 34             key = scanner.next();
 35 
 36             //switch 控制
 37             switch (key) {
 38                 case "1":
 39                     System.out.println(details);
 40                     break;
 41                 case "2":
 42                     System.out.println("收益入账金额");
 43                     money = scanner.nextDouble();
 44                     //money范围校验
 45                     if (money <= 0) {
 46                         System.out.println("收益入账金额范围 需要 大于 0");
 47                         break;
 48                     }
 49                     balance += money;
 50                     //拼接信息到收益入账
 51                     date = new Date();//获取当前日期
 52                     details += "
收益入账	+" + money + "	" + sdf.format(date) + "	" + balance;
 53                     break;
 54                 case "3":
 55                     System.out.println("3 消费");
 56                     money = scanner.nextDouble();
 57                     //money范围校验
 58                     if (money <= 0 || money > balance) {
 59                         if (money <= 0){
 60                             System.out.println("您的消费金额应该 大于 0");
 61                             break;
 62                         }else{
 63                             System.out.println("消费不能透支余额!");
 64                             break;
 65                         }
 66                     }
 67 
 68                     System.out.println("消费说明");
 69                     note = scanner.next();
 70                     balance -= money;
 71                     date = new Date();//获取当前日期
 72                     details += "
" + note + "	-" + money + "	" + sdf.format(date) + "	" + balance;
 73                     break;
 74                 case "4":
 75                     System.out.println("4 退     出");
 76 
 77                     while (true) {
 78                         System.out.println("你确定要退出吗?y/n");
 79                         choice = scanner.next();
 80                         if ("y".equals(choice) || "n".equals(choice)) {
 81                             break;
 82                         }
 83 
 84                     }
 85                     //当用户退出while后再判断choice是y还是n,就可以决定是否退出
 86                     if ("y".equals(choice)) {
 87                         loop = false;
 88                     }
 89 
 90                     break;
 91                 default:
 92                     System.out.println("选择有误，请重新选择");
 93                     break;
 94             }
 95         } while (loop);
 96         System.out.println("==============退出了零钱通项目==============");
 97 
 98 
 99     }
100 }