java - 最有效的基本日期验证和转换程序？

Question

我计划用 Java 创建一个程序，用于确定输入的年份是否为闰年以及有效日期。我希望将该日期转换为完整的书面名称(4/2/2013 = 2013 年 4 月 2 日)，然后确定该日期在一年中的数字(4/2/2013 = 第 92 天)。

有很多程序可以执行其中一种或另一种操作，但我正在学习如何将它们全部结合在一起(如果可能的话)的方法/想法。

要检查闰年，这就是我使用的:

public class LeapYear {
    public static void main (String[] args) {
    int theYear;
    System.out.print("Enter the year: ");
    theYear = Console.in.readInt();
    if (theYear < 100) {
        if (theYear > 40) {
        theYear = theYear + 1900;
        }
        else {
        theYear = theYear + 2000;
        }
    }
    if (theYear % 4 == 0) {
        if (theYear % 100 != 0) {
        System.out.println(theYear + " is a leap year.");
        }
        else if (theYear % 400 == 0) {
        System.out.println(theYear + " is a leap year.");
        }
        else {
        System.out.println(theYear + " is not a leap year.");
        }
    }
    else {
        System.out.println(theYear + " is not a leap year.");
    }
    }

}

我意识到我需要对其进行一些更改以读取一年中的月份和日期，但对于这种情况，我只是检查年份。我怎样才能将输入的相同日期转换为完整的书面姓名？我是否必须创建一个 if 语句，例如:

if (theMonth == 4){
     System.out.println("April");
         if (theDay == 2){
          System.out.print(" 2nd, " + theYear + ".");
         }
    }

这似乎是很多硬编码工作。我正在尝试限制所需的硬编码量，以便我可以获得类似的内容:

Output:
 Valid entry (4/2/2013).
 It is April 2nd, 2013.
 It is not a leap year.
 It is day 92.

如果出现错误，例如无效日期，我希望程序重新提示用户，直到收到有效条目，而不是必须运行程序(在写入“退出”时会结束程序)。

我想我可能只是为主方法(获取日期)创建不同的类，检查它是否是闰年，转换方法，也许还有验证方法。

Answer 1

public void testFormatDate() throws ParseException {
        final String[] suffixes =
                //    0     1     2     3     4     5     6     7     8     9
                { "th", "st", "nd", "rd", "th", "th", "th", "th", "th", "th",
                        //    10    11    12    13    14    15    16    17    18    19
                        "th", "th", "th", "th", "th", "th", "th", "th", "th", "th",
                        //    20    21    22    23    24    25    26    27    28    29
                        "th", "st", "nd", "rd", "th", "th", "th", "th", "th", "th",
                        //    30    31
                        "th", "st" };
        SimpleDateFormat sdf = new SimpleDateFormat("MM/dd/yyyy");
        SimpleDateFormat odf = new SimpleDateFormat("MMMM"); // Gives month name.
        Calendar dayEntered = new GregorianCalendar();
        dayEntered.setTime(sdf.parse("04/02/2013"));
        System.err.println("You chose date: " + odf.format(dayEntered.getTime()) + " " + dayEntered.get(Calendar.DAY_OF_MONTH) + suffixes[dayEntered.get(Calendar.DAY_OF_MONTH)]
        + " " + dayEntered.get(Calendar.YEAR));
        System.err.println("This is " + (((GregorianCalendar)dayEntered).isLeapYear(dayEntered.get(Calendar.YEAR)) ? "" : "not ") + "a leap year.");

        System.err.println("This is day: " + dayEntered.get(Calendar.DAY_OF_YEAR));
    }