有人能帮我修一下这个程序吗

Question

我必须创建程序，这样我就可以输入3个字母加上像“Jan1999”这样的一年，并显示日历。

package assignment.pkg2;

import java.util.Scanner;

public class Assignment2 {
    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 boolean isLeapYear(int year) {
        int month = 0;
        int s = getDaysIn(month, year);
        return year % 4 == 0 && (year % 100 != 0) || (year % 400 == 0);
    }

    public static int getDaysIn(int month, int year) {
        switch (month) {
            case 1:
                return 31;
            case 2:
                if (isLeapYear(month)) {
                    return 29;
                } else {
                    return 28;
                }
            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 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(month, year);
        }
        int startday = (days + 1) % 7 + 1;
        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 c = new Scanner(System.in);
        System.out.print("Give the first three letters of a month and enter the year: ");
        String month, year;
        month = c.next();
        year = c.next();
        int yearno = Integer.parseInt(year);
        int monthno = getMonthNumber(month);
        displayCalendar(monthno, yearno);
        System.out.println();
        System.out.println("Do you want to continue? y/n ");
    }
}

Answer 1

大部分代码都很简单，诀窍在于验证输入是否为指定格式的有效日期。你可以在YearMonth课上做到这一点。然后您可以从中创建一个Calendar类。

如果您使用的是Java8，请尝试以下操作：

    String myInputString = null;

    try
    {
       BufferedReader bufferRead = new BufferedReader(new InputStreamReader(System.in));
       myInputString = bufferRead.readLine();
    }
    catch(Exception e)
    {
        System.out.print(e);
    }

    YearMonth myYM = null;
    Calendar calendar = null;

    try
    {
      DateTimeFormatterBuilder fmb = new DateTimeFormatterBuilder();
      fmb.parseCaseInsensitive();
      fmb.append(DateTimeFormatter.ofPattern("MMM yyyy"));

      DateTimeFormatter formatter = fmb.toFormatter();

      myYM = YearMonth.parse(myInputString.trim(), formatter);
      calendar = new GregorianCalendar();
      calendar.clear();
      calendar.set(myYM.getYear(), myYM.getMonthValue(), 1);
    }
    catch(DateTimeParseException e)
    {
        // Invalid date format
        System.out.println(e);
    }
}