如何根据月份和年份填充天组合框? [英] How to populate days combobox based on month and year?

问题描述

private void buildMonthsList(cmbMonth monthsList) {
    for (int monthCount = 0; monthCount < 12; monthCount++)
        monthsList.addItem(Const.MONTHS[monthCount]);
}

public boolean DaysComboBox (int year)
{
    Calendar cal = Calendar.getInstance();
    int months = cal.get(Calendar.MONTH);

    year = (int) cmbYear.getSelectedItem();
    boolean leap = false;

    if(year % 4 == 0)
    {
        if( year % 100 == 0)
        {
            // year is divisible by 400, hence the year is a leap year
            if ( year % 400 == 0)
            {
                leap = true;
            }
            else {
                leap = false;
            }
        }
        else {
            leap = true;
        }
    }
    else {
        leap = false;
    }

    return leap;
}

我在学校里有一个重要的Java Swing程序需要帮助.

I need some help with a Java Swing program I have for school which is important.

如何根据月份和年份(包括leap年)填写天数?我使用了3个单独的组合框，一个组合用于几天，另一个组合用于几个月，另一个组合用于多年.还应该从方法中调用它.

How can you fill in the number of days according to the month and year including leap year? I used 3 separate combo boxes, one for the days, another one for the months and another for the years. It should also be called from a method.

推荐答案

最佳"解决方案是利用可用功能.

The "best" solution is take advantage of the available functionality.

Java 8+引入了java.time API，它取代了基于Calendar和Date的API

Java 8+ introduced the java.time API, which replaces the Calendar and Date based APIs

例如，使用 YearMonth 类…

For example, something like this, using YearMonth class…

for (int year = 2010; year <= 2020; year++) {
    YearMonth ym = YearMonth.of(year, Month.FEBRUARY);
    System.out.println(year + " = " + ym.lengthOfMonth());
}

将打印...

2010 = 28
2011 = 28
2012 = 29
2013 = 28
2014 = 28
2015 = 28
2016 = 29
2017 = 28
2018 = 28
2019 = 28
2020 = 29

由此，您可以简单地创建一个新的ComboBoxModel，用所需的值填充并将其应用于JComboBox的实例-请参见

From this, you can simply create a new ComboBoxModel, fill it with the values you need and apply it to the instance of JComboBox - see How to Use Combo Boxes for more details.

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