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："); } else break; } 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; }} public class Account{public static void main(String[] args){String details = "收支t账户金额t收支金额t说 明n";int balance = 10000;boolean flag = true;while(flag){System.out.println("n----------------家庭收支记账软件-----------------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.println(" 请选择<1—4>：n");char key = Utility.readMenuSelection();switch(key){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 addAmount = Utility.readNumber();System.out.print("本次收入说明：");String addDesc = Utility.readString();balance += addAmount;details += "收入" + "t" + balance + "tt" + addAmount + "tt" + addDesc + "n";System.out.println("---------------------登记完成---------------------");break;case '3':System.out.print("本次支出金额：");int subAmount = Utility.readNumber();System.out.print("本次支出说明：");String subDesc = Utility.readString();balance -= subAmount;details += "支出" + "t" + balance + "tt" + subAmount + "tt" + subDesc + "n";System.out.println("---------------------登记完成---------------------");break;case '4':System.out.println("确认是否退出(Y/N)：");char isExit = Utility.readConfirmSelection();if(isExit == 'Y'){flag = false;}break;}}}}