Java模仿微信實現零錢通簡易功能(兩種版本)
最近剛剛復習瞭一下Java的面向對象三大特性,這裡跟著hsp做個小零錢通實踐一下,以下記錄瞭學習和編寫過程
1. 需求描述
使用Java 開發零錢通項目, 模仿微信實現簡易功能，可以完成收益入賬，消費，查看明細，退出系統等功能，先按照一般方法寫，後期在改進為OOP
預期界面：（實際可能不同）
2. 需求分析
面對這樣一個需求，先化繁為簡
- 寫一個菜單
- 完成零錢通明細.
- 完成收益入賬
- 消費
- 退出
- 用戶輸入4退出時，給出提示”你確定要退出嗎? y/n”，必須輸入正確的y/n ，否則循環輸入指令，直到輸入y 或者 n
- 在收益入賬和消費時，判斷金額是否合理，並給出相應的提示
3. 實現零錢通主要功能
3.1 寫一個菜單
先完成顯示菜單，並可以選擇菜單，並且給出對應提示
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 零錢通明細
思路
(1) 可以把收益入賬和消費保存到數組
(2) 可以使用對象
(3) 簡單的話可以使用String拼接
這裡直接采取第三種方式
改變一下switch的case1
String details = "-----------------零錢通明細------------------";
case "1":
System.out.println(details);
break;
3.3 收益入賬
完成收益入賬
定義新的變量
double money = 0;
double balance = 0;
Date date = null; // date 是 java.util.Date 類型，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;
//拼接收益入賬信息到 details
date = new Date(); //Get the current time
details += "\n收益入賬\t+" + money + "\t" + sdf.format(date)+ "\t" + balance;
break;
效果演示：
保證入賬>0
3.4 消費
定義新的變量
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 用戶退出改進
給出確認,是否要退出
用戶輸入4退出時，給出提示”你確定要退出嗎? y/n”，必須輸入正確的y/n ，
否則循環輸入指令，直到輸入y 或者 n
(1) 定義一個變量 choice, 接收用戶的輸入
(2) 使用 while + break, 來處理接收到的輸入時 y 或者 n
(3) 退出while後，再判斷choice是y還是n ,就可以決定是否退出
(4) 建議一段代碼完成功能，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("你確定要退出嗎? 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 改進金額判斷
收入時
if (money <= 0) {
System.out.println("The income entry amount must be greater than 0");
break;
}
支出時
if (money <= 0 || money > balance) {
System.out.println("Your consumption amount should be 0-" + balance);
break;
}
效果演示
4. 面向過程版實現
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) 可以把收益入賬和消費，保存到數組 (2) 可以使用對象 (3) 簡單的話可以使用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 類型，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("你確定要退出嗎? 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. 優化成OOP版
很多東西可以直接復制過來變成方法,把原來的改過來是簡單的
5.1 實現OOP版
那麼先有一個執行的主類SmallChangeSysApp
//Call the object directly and display the main menu
public class SmallChangeSysApp {
public static void main(String[] args) {
new SmallChangeSysOOP().mainMenu();
}
}
還有一個類專門是對象,我們叫它為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的好處
OOP版主函數很簡單,隻要new這個對象就可以瞭,關於這個對象的其他方法也好屬性也好,不用放在主函數裡面,那樣在主函數也可以自由加上想加得到內容,未來假如有他人要用,不用把整個文件拷過去,隻要把類交給對方即可,這樣擴展和可讀性大大提升,要加什麼功能就再寫方法原先的擴展功能很麻煩,要來回切
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