java小项目：简单的收入明细记事本，超级简单（不涉及数据库，通过字符串来记录）

一、效果

二、代码

2.1   Acount类

package com.demo1;public class Acount {public static void main(String[] args) {String details = "收支\t账户金额\t收支金额\t说    明\n";  //通过字符串来记录收入明细int balance = 10000;boolean loopFlag = true;//控制循环结束while (loopFlag){System.out.println("\n---------------------记账-----------------\n");System.out.println("                   1 收支明细");System.out.println("                   2 登记收入");System.out.println("                   3 登记支出");System.out.println("                   4 退    出\n");System.out.print("                   请选择(1-4)：");char selection = Utility.readMenuSelection();//通过工具类获取用户的选择switch (selection){case '1':System.out.println("-----------------当前收支明细记录-----------------");System.out.println(details);System.out.println("--------------------------------------------------");break;case '2':System.out.print("本次收入金额：");int amount1 = Utility.readNumber();System.out.print("本次收入说明：");String desc1 = Utility.readString();balance += amount1;details += "收入\t" + balance + "\t\t" +amount1 + "\t\t" + desc1 + "\n";System.out.println("---------------------登记完成---------------------");break;case '3':System.out.print("本次支出金额：");int amount2 = Utility.readNumber();System.out.print("本次支出说明：");String desc2 = Utility.readString();balance -= amount2;details += "支出\t" + balance + "\t\t" +amount2 + "\t\t" + desc2 + "\n";System.out.println("---------------------登记完成---------------------");break;case '4':System.out.print("确认是否退出(Y/N)：");char yn = Utility.readConfirmSelection();if (yn == 'Y') loopFlag = false;break;}}}
}

2.2  工具类  Utilit

package com.demo1;import java.util.Scanner;
/**Utility工具类：将不同的功能封装为方法，就是可以直接通过调用方法使用它的功能，而无需考虑具体的功能实现细节。*/
public class Utility {private static Scanner scanner = new Scanner(System.in);/**用于界面菜单的选择。该方法读取键盘，如果用户键入’1’-’4’中的任意字符，则方法返回。返回值为用户键入字符。*/public static char readMenuSelection() {char c;for (; ; ) {String str = readKeyBoard(1);c = str.charAt(0);if (c != '1' && c != '2' && c != '3' && c != '4') {System.out.print("选择错误，请重新输入：");}elsebreak;}return c;}/**用于收入和支出金额的输入。该方法从键盘读取一个不超过4位长度的整数，并将其作为方法的返回值。*/public static int readNumber() {int n;for (; ; ) {String str = readKeyBoard(4);try {n = Integer.parseInt(str);break;} catch (NumberFormatException e) {System.out.print("数字输入错误，请重新输入：");}}return n;}/**用于收入和支出说明的输入。该方法从键盘读取一个不超过8位长度的字符串，并将其作为方法的返回值。*/public static String readString() {String str = readKeyBoard(8);return str;}/**用于确认选择的输入。该方法从键盘读取‘Y’或’N’，并将其作为方法的返回值。*/public static char readConfirmSelection() {char c;for (; ; ) {String str = readKeyBoard(1).toUpperCase();c = str.charAt(0);if (c == 'Y' || c == 'N') {break;} else {System.out.print("选择错误，请重新输入：");}}return c;}private static String readKeyBoard(int limit) {String line = "";while (scanner.hasNext()) {line = scanner.nextLine();if (line.length() < 1 || line.length() > limit) {System.out.print("输入长度（不大于" + limit + "）错误，请重新输入：");continue;}break;}return line;}
}

2.3  类的结构