Java微信零钱通
言之命至9012 人气:0最近刚刚复习了一下Java的面向对象三大特性,这里跟着hsp做个小零钱通实践一下,以下记录了学习和编写过程
1. 需求描述
使用Java 开发零钱通项目, 模仿微信实现简易功能,可以完成收益入账,消费,查看明细,退出系统等功能,先按照一般方法写,后期在改进为OOP
预期界面:(实际可能不同)
2. 需求分析
面对这样一个需求,先化繁为简
- 写一个菜单
- 完成零钱通明细.
- 完成收益入账
- 消费
- 退出
- 用户输入4退出时,给出提示"你确定要退出吗? y/n",必须输入正确的y/n ,否则循环输入指令,直到输入y 或者 n
- 在收益入账和消费时,判断金额是否合理,并给出相应的提示
3. 实现零钱通主要功能
3.1 写一个菜单
先完成显示菜单,并可以选择菜单,并且给出对应提示
public static void main(String[] args) { // define related variables Scanner scanner = new Scanner(System.in); String key = ""; boolean loop = true; do { System.out.println("==========Small Change Menu=========="); System.out.println("\t\t\t1 show change details"); System.out.println("\t\t\t2 income entry"); System.out.println("\t\t\t3 consumption"); System.out.println("\t\t\t4 exit"); System.out.println("please choose 1-4:"); key = scanner.next(); //use switch to control switch (key) { case "1": System.out.println("1 show change details"); break; case "2": System.out.println("2 income entry"); break; case "3": System.out.println("3 consumption"); break; case "4": System.out.println("4 exit"); System.out.println(" you have exit the SmallChange"); loop = false; break; default: System.out.println("err please choose again"); } } while (loop); }
3.2 零钱通明细
思路
(1) 可以把收益入账和消费保存到数组
(2) 可以使用对象
(3) 简单的话可以使用String拼接
这里直接采取第三种方式
改变一下switch的case1
String details = "-----------------零钱通明细------------------";
case "1": System.out.println(details); break;
3.3 收益入账
完成收益入账
定义新的变量
double money = 0; double balance = 0; Date date = null; // date 是 java.util.Date 类型,表示日期 //if you don't like the default format of displaying date ,change it with sdf SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm");
修改switch中的case2
System.out.print("Income recorded amount:"); money = scanner.nextDouble(); //the range of money should be limited //give the hits of the illegal money value 就直接break balance += money; //拼接收益入账信息到 details date = new Date(); //Get the current time details += "\n收益入账\t+" + money + "\t" + sdf.format(date)+ "\t" + balance; break;
效果演示:
保证入账>0
3.4 消费
定义新的变量
String note = "";
修改switch中的case3
case "3": System.out.print("Consumption amount:"); money = scanner.nextDouble(); //the range of money should be limited System.out.print("Consumption Description:"); note = scanner.next(); balance -= money; //Splicing consumption information to details date = new Date();//Get the current time details += "\n"+note + "\t-" + money + "\t" + sdf.format(date) + "\t" + balance; break;
效果演示:
3.5 用户退出改进
给出确认,是否要退出
用户输入4退出时,给出提示"你确定要退出吗? y/n",必须输入正确的y/n ,
否则循环输入指令,直到输入y 或者 n
(1) 定义一个变量 choice, 接收用户的输入
(2) 使用 while + break, 来处理接收到的输入时 y 或者 n
(3) 退出while后,再判断choice是y还是n ,就可以决定是否退出
(4) 建议一段代码完成功能,不混在一起
case "4": String choice = ""; while (true) { //The user is required to enter Y / N, otherwise it will cycle all the time System.out.println("你确定要退出吗? y/n"); choice = scanner.next(); if ("y".equals(choice) || "n".equals(choice)) { break; } //scheme 2 // if("y".equals(choice)) { // loop = false; // break; // } else if ("n".equals(choice)) { // break; // } } if (choice.equals("y")) { loop = false; } break;
效果演示:
3.6 改进金额判断
收入时
if (money <= 0) { System.out.println("The income entry amount must be greater than 0"); break; }
支出时
if (money <= 0 || money > balance) { System.out.println("Your consumption amount should be 0-" + balance); break; }
效果演示
4. 面向过程版实现
import java.text.SimpleDateFormat; import java.util.Date; import java.util.Scanner; public class SmallChangeSys { // try to reduce complexity to simplicity //1. First complete the display menu, // and you can select the menu to give the corresponding prompt //2. Complete change details //3. Complete income entry //4. consumption //5. exit //6. When the user enters 4 to exit, the prompt "are you sure you want to exit? // Y / N" will be given. You must enter the correct Y / N, // otherwise cycle the input instruction until y or n is entered //7. When the income is recorded and consumed, // judge whether the amount is reasonable and give corresponding tips public static void main(String[] args) { // define related variables Scanner scanner = new Scanner(System.in); String key = ""; boolean loop = true; //2. complete the change details //(1) 可以把收益入账和消费,保存到数组 (2) 可以使用对象 (3) 简单的话可以使用String拼接 String details = "-----------------Change details------------------"; //3. complete income entry double money = 0; double balance = 0; Date date = null; // date 是 java.util.Date 类型,表示日期 //if you don't like the default format of displaying date ,change it with sdf SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm"); //4. consumption //define new variable,store the reason why consume String note = ""; do { System.out.println("\n==========Small Change Menu=========="); System.out.println("\t\t\t1 show change details"); System.out.println("\t\t\t2 income entry"); System.out.println("\t\t\t3 consumption"); System.out.println("\t\t\t4 exit"); System.out.println("please choose 1-4:"); key = scanner.next(); //use switch to control switch (key) { case "1": System.out.println(details); break; case "2": System.out.print("Income recorded amount:"); money = scanner.nextDouble(); //the range of money should be limited //commonly use <if> to judge the wrong situation make the code easy to read //give the hits of the illegal money value 就直接break if (money <= 0) { System.out.println("The income entry amount must be greater than 0"); break; } balance += money; //Splicing consumption information to details date = new Date(); //Get the current time details += "\n" + "Income " + "\t" + "+" + money + "\t" + sdf.format(date) + "\t" + balance; break; case "3": System.out.print("Consumption amount:"); money = scanner.nextDouble(); //the range of money should be limited if (money <= 0 || money > balance) { System.out.println("Your consumption amount should be 0-" + balance); break; } System.out.print("Consumption Description:"); note = scanner.next(); balance -= money; //Splicing consumption information to details date = new Date();//Get the current time details += "\n" + note + "\t-" + money + "\t" + sdf.format(date) + "\t" + balance; break; case "4": String choice = ""; while (true) { //The user is required to enter Y / N, otherwise it will cycle all the time System.out.println("你确定要退出吗? y/n"); choice = scanner.next(); if ("y".equals(choice) || "n".equals(choice)) { break; } //scheme 2 // if("y".equals(choice)) { // loop = false; // break; // } else if ("n".equals(choice)) { // break; // } } if (choice.equals("y")) { loop = false; } break; default: System.out.println("err please choose again"); } } while (loop); System.out.println(" you have exit the SmallChange"); } }
5. 优化成OOP版
很多东西可以直接复制过来变成方法,把原来的改过来是简单的
5.1 实现OOP版
那么先有一个执行的主类SmallChangeSysApp
//Call the object directly and display the main menu public class SmallChangeSysApp { public static void main(String[] args) { new SmallChangeSysOOP().mainMenu(); } }
还有一个类专门是对象,我们叫它为SmallChangeSysOOP
import java.text.SimpleDateFormat; import java.util.Date; import java.util.Scanner; /** * This class is used to complete various functions of zero money pass * Using OOP (object-oriented programming) * Each function corresponds to a method */ public class SmallChangeSysOOP { //basic variables boolean loop = true; Scanner scanner = new Scanner(System.in); String key = ""; //display details String details = "-----------------Change details------------------"; //income double money = 0; double balance = 0; Date date = null; SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm"); // consume String note = ""; public void mainMenu() { do { System.out.println("\n================Small Change Menu(OOP)==============="); System.out.println("\t\t\t1 show change details"); System.out.println("\t\t\t2 income entry"); System.out.println("\t\t\t3 consumption"); System.out.println("\t\t\t4 exit"); System.out.println("please choose 1-4:"); key = scanner.next(); switch (key) { case "1": this.detail(); break; case "2": this.income(); break; case "3": this.pay(); break; case "4": this.exit(); break; default: System.out.println("Choose the wrong number please choose again"); } } while (loop); } public void detail() { System.out.println(details); } public void income() { System.out.print("Income recorded amount:"); money = scanner.nextDouble(); if (money <= 0) { System.out.println("The income entry amount must be greater than 0"); return; //exit and do not execute next sentence.change break to return } balance += money; date = new Date(); details += "\nIncome \t+" + money + "\t" + sdf.format(date) + "\t" + balance; } public void pay() { System.out.print("Consumption amount:"); money = scanner.nextDouble(); if (money <= 0 || money > balance) { System.out.println("Your consumption amount should be 0-" + balance); return; } System.out.print("consumption description:"); note = scanner.next(); balance -= money; date = new Date(); details += "\n" + note + "\t-" + money + "\t" + sdf.format(date) + "\t" + balance; } //退出 public void exit() { //When the user enters 4 to exit, the prompt "are you sure you want to exit? // Y / N" will be given. You must enter the correct Y / n String choice = ""; while (true) { System.out.println("are you really gonna exit? y/n"); choice = scanner.next(); if ("y".equals(choice) || "n".equals(choice)) { break; } //scheme 2 // if("y".equals(choice)) { // loop = false; // break; // } else if ("n".equals(choice)) { // break; // } } if (choice.equals("y")) { loop = false; } } }
5.2 OOP的好处
OOP版主函数很简单,只要new这个对象就可以了,关于这个对象的其他方法也好属性也好,不用放在主函数里面,那样在主函数也可以自由加上想加得到内容,未来假如有他人要用,不用把整个文件拷过去,只要把类交给对方即可,这样扩展和可读性大大提升,要加什么功能就再写方法原先的扩展功能很麻烦,要来回切
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