如何在 Java GWT 中进行日历操作？如何在日期中添加天数？
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How to do calendar operations in Java GWT? How to add days to a Date?
提问by Witek
Since GWT does not provide the GregorianCalendar class, how to do calendar operations on the client?
由于GWT没有提供GregorianCalendar类，那么如何在客户端做日历操作呢？
I have a Date aand I want the Date, which is ndays after a.
我有一个日期a，我想日期，这是n几天之后a。
Examples:
例子：
a (2000-01-01) + n (1) -> 2000-01-02
a (2000-01-01) + n (31) -> 2000-02-01
采纳答案by Tony BenBrahim
Updated answer for GWT 2.1
GWT 2.1 的更新答案
final Date dueDate = new Date();
CalendarUtil.addDaysToDate(dueDate, 21);
Edit: the fully qualified name of this class is com.google.gwt.user.datepicker.client.CalendarUtil.
编辑：此类的完全限定名称是com.google.gwt.user.datepicker.client.CalendarUtil。
回答by Chris Lercher
The answer that Google seems to use (currently), is:
谷歌似乎（目前）使用的答案是：
@SuppressWarnings("deprecation") // GWT requires Date
public static void addDaysToDate(Date date, int days) {
date.setDate(date.getDate() + days);
}
This is from the class com.google.gwt.user.datepicker.client.CalendarUtil, which is used by com.google.gwt.user.datepicker.client.DatePicker. I imagine, that there will be problems involved, when doing calculations in different timezones.
这是来自类com.google.gwt.user.datepicker.client.CalendarUtil，由com.google.gwt.user.datepicker.client.DatePicker. 我想，在不同的时区进行计算时会涉及到问题。
Lots of people have already voted for some kind of Joda time for GWT: http://code.google.com/p/google-web-toolkit/issues/detail?id=603. The currently last comment states, that there's a new fork of goda time, maybe we should really check it out.
很多人已经为 GWT 投票支持某种 Joda 时间：http: //code.google.com/p/google-web-toolkit/issues/detail? id=603 。当前最后一条评论指出，goda 时间有一个新的分支，也许我们真的应该检查一下。
回答by user471824
I've created a rough implementation that emulates TimeZone, Calendar, and Locale. Feel free to try it out here:
我创建了一个模拟 TimeZone、Calendar 和 Locale 的粗略实现。随意在这里尝试一下：
回答by Norm Wright
private static final long MILLISECONDS_IN_SECOND = 1000l;
private static final long SECONDS_IN_MINUTE = 60l;
private static final long MINUTES_IN_HOUR = 60l;
private static final long HOURS_IN_DAY = 24l;
private static final long MILLISECONDS_IN_DAY = MILLISECONDS_IN_SECOND *
SECONDS_IN_MINUTE *
MINUTES_IN_HOUR *
HOURS_IN_DAY;
public Date addDays (Date date, days)
{
return new Date (date.getTime () + (days * MILLISECONDS_IN_DAY));
}
this will work with leap years but will eventuallystray by milliseconds on milleniums when we add or drop leap seconds.
这将适用于闰年，但当我们添加或删除闰秒时，最终会在千禧年中偏离毫秒。
