问题描述

我想为一个表单构建一个日期小部件，它有一个包含月、日、年的选择列表.由于列表根据月份和年份而有所不同，因此我无法将其硬编码为 31 天.(例如 2 月有 28 天而不是 30 或 31 天，有些年份甚至是 29 天)如何使用日历或 joda 对象为我构建这些列表.

I want to build a date widget for a form, which has a select list of months, days, years. since the list is different based on the month and year, i cant hard code it to 31 days. (e.g february has 28 days not 30 or 31 and some years even 29 days) How can I use the calendar or joda object to build me these lists.

推荐答案

我强烈建议您避免使用 Java 中内置的日期和时间 API.

I strongly recommend that you avoid the built-in date and time APIs in Java.

改为使用 Joda Time.这个库类似于(希望如此！)进入 Java 7 的库，并且比内置 API 更易于使用.

Instead, use Joda Time. This library is similar to the one which will (hopefully!) make it into Java 7, and is much more pleasant to use than the built-in API.

现在，您想知道特定月份的天数是基本问题吗?

Now, is the basic problem that you want to know the number of days in a particular month?

这是代码(带有示例):

Here's the code (with a sample):

import org.joda.time.*;
import org.joda.time.chrono.*;

public class Test   
{
    public static void main(String[] args)
    {        
        System.out.println(getDaysInMonth(2009, 2));
    }

    public static int getDaysInMonth(int year, int month)
    {
        // If you want to use a different calendar system (e.g. Coptic)
        // this is the code to change.
        Chronology chrono = ISOChronology.getInstance();
        DateTimeField dayField = chrono.dayOfMonth();        
        LocalDate monthDate = new LocalDate(year, month, 1);
        return dayField.getMaximumValue(monthDate);
    }
}

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