如何使程序在错误的情况下多次要求输入日期

Question

2.2.显示日历后，程序必须询问用户是否要输入另一个日期（是否继续？）

2.3.用户必须用大小写字母的任意组合回答是、否、y或n

2.4.如果给出了无效的答案，则必须通知用户该答案不可接受，然后再次提示用户输入另一个答案。如果给出了三个以上连续的错误答案，程序必须以适当的错误消息终止

这是我目前所拥有的

public static int getMonthNumber(String s) {
    if (s.equalsIgnoreCase("jan")) {
        return 1;
    }
    if (s.equalsIgnoreCase("feb")) {
        return 2;
    }
    if (s.equalsIgnoreCase("mar")) {
        return 3;
    }
    if (s.equalsIgnoreCase("apr")) {
        return 4;
    }
    if (s.equalsIgnoreCase("may")) {
        return 5;
    }
    if (s.equalsIgnoreCase("jun")) {
        return 6;
    }
    if (s.equalsIgnoreCase("jul")) {
        return 7;
    }
    if (s.equalsIgnoreCase("aug")) {
        return 8;
    }
    if (s.equalsIgnoreCase("sep")) {
        return 9;
    }
    if (s.equalsIgnoreCase("oct")) {
        return 10;
    }
    if (s.equalsIgnoreCase("nov")) {
        return 11;
    }
    if (s.equalsIgnoreCase("dec")) {
        return 12;
    } else {
        System.out.println("Not valid month!");

    }
    return 0;
}

    public static int getDaysIn(int month, int year) {
    switch (month) {
        case 1:
            return 31;
        case 2:
            if (isLeapYear(month)) {
                return 28;
            } else {
                return 29;
            }
        case 3:
            return 31;
        case 4:
            return 30;
        case 5:
            return 31;
        case 6:
            return 30;
        case 7:
            return 31;
        case 8:
            return 31;
        case 9:
            return 30;
        case 10:
            return 31;
        case 11:
            return 30;
        case 12:
            return 31;
        default:
            return -1;
    }
}

    public static boolean isLeapYear(int year) {
    int month = 0;
    int s = getDaysIn(month, year);
    return year % 4 == 0 && (year % 100 != 0) || (year % 400 == 0);
}

    public static String getMonthName(int month) {
    switch (month) {
        case 1:
            return "January";
        case 2:
            return "February";
        case 3:
            return "March";
        case 4:
            return "April";
        case 5:
            return "May";
        case 6:
            return "June";
        case 7:
            return "July";
        case 8:
            return "August";
        case 9:
            return "September";
        case 10:
            return "October";
        case 11:
            return "November";
        case 12:
            return "December";
        default:
            return "Invalid month.";
    }
    }

    public static int getStartDay(int month, int year) {
    int days = 0;
    for (int i = 1900; i < year; i++) {
        days = days + 365;
        if (isLeapYear(i)) {
            days = days + 1;

        }
    }
    for (int i = 1; i < month; i++) {
        days = days + getDaysIn(i, year);
    }
    int startday = (days % 7) + 2;
    return startday;

}

    public static void displayCalendar(int month, int year) {
    String monthName = getMonthName(month);
    int startDay = getStartDay(month, year);
    int monthDays = getDaysIn(month, year);

    System.out.println("   Sun   Mon   Tue   Wed   Thu   Fri   Sat");
    int weekDay = startDay - 1;
    for (int i = 1; i <= startDay; i = i + 1) {
        System.out.print("    ");
    }
    for (int x = 1; x <= monthDays; x++) {
        weekDay = weekDay + 1;
        if (weekDay > 7) {
            System.out.println();
            weekDay = 1;
        }
        System.out.format("   %3d", x);
    }
    if (weekDay > 7) {
        System.out.println();
    }
}

    public static void main(String[] args) {
    Scanner scan = null;
    Scanner kb = new Scanner(System.in);
    System.out.print("Give the first three letters of a month and enter the year: ");
    System.out.print(" ");
    String month;
    int year;
    month = kb.next();
    year = kb.nextInt();
    int yearno = year;
    int monthno = getMonthNumber(month);
    if (year > 2099) 
        System.out.println("                 Invalid Year!");

    if (year < 1900);
        System.out.println("                 Invalid Year!"); 



     System.out.println();
    displayCalendar(monthno, yearno);
    System.out.println();
    System.out.println();
    System.out.println("Do you want to continue? y/n ");

如果年份是错误的，它会打印无效年份，但现在m坚持如何在结束程序之前再次询问3个领带/如果用户在3次尝试中的一次输入正确的日期，则继续。到目前为止，在我的程序中，如果用户输入了有效的日期，就会打印出正确的日历

Answer 1

你需要做的是循环

  int monthno = 0;
  while (monthno == 0) {
     System.out.print("Give the first three letters of a month");
     month = kb.next();
     monthno = getMonthNumber(month);          
 }

并对其他输入执行同样的操作

顺便说一句，如果在ArrayList中保持tourmonths，然后简单地执行get以获取值，那么代码将非常干净。它要么存在，要么不存在。