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。
*/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;}
}class  familytest
{public static void main(String[] args) {boolean isflag=true;//用于登记用户的收入和支出的详情String details="收支 账户金额 收支金额 说 明 "+"\n";int balance=10000;while(isflag){System.out.println("-----------------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.print("                   请选择(1-4)：");//获取用户方法1-4char selection=Utility.readMenuSelection();switch(selection){case '1'://System.out.println("1 收支明细");System.out.println("-----------------当前收支明细记录-----------------");//System.out.println("收支 账户金额 收支金额 说 明");System.out.println(details);System.out.println("----------------------------------");break;case '2'://System.out.println("2 登记收入");System.out.print("本次收入金额：");int money=Utility.readNumber();System.out.print("本次收入说明：");String info    =Utility.readString();//处理balance，原有金额balance += money;     //处理详情details += (("收入\t"+balance+"\t"+money+"\t"+info)+"\n");System.out.println("---------------登记完成---------------\n");break;case '3'://System.out.println("3 登记支出");System.out.print("本次支出金额：");int money1=Utility.readNumber();System.out.print("本次支出说明：");String info1  =Utility.readString();//处理支出，balanceif(balance>=money1){balance -= money1;details += (("收入\t"+balance+"\t"+money1+"\t"+info1)+"\n");}else{System.out.println("支出超出额度，支付失败");}break;case '4':System.out.println("确认是否退出Y/N:");char isexit=Utility.readConfirmSelection();if(isexit=='Y'){isflag=false;}}}}
}

接下来就是各个功能的实现