Java 设置日历实例的时间
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Setting time for calendar instance
提问by shmoula
I'm trying to set time to Calendar instance, but I'm experiencing weird behavior. Let's check some example:
我正在尝试为 Calendar 实例设置时间，但我遇到了奇怪的行为。让我们检查一些例子：
Calendar c = Calendar.getInstance();
//c.setTime(date);
c.set(date.getYear(), (date.getMonth() - 1), date.getDay());
int dayOfWeek = c.get(Calendar.DAY_OF_WEEK);
When I set time with setTime(), it sets wrong date. The second (and deprecated) set(year, month, day) works correctly. I've never met with this before - I thought that it uses default timezone in both cases, so it should be the same. Can someone explain it to me please?
当我使用 setTime() 设置时间时，它设置了错误的日期。第二个（和已弃用的）集合（年、月、日）正常工作。我以前从未遇到过这个 - 我认为它在两种情况下都使用默认时区，所以它应该是相同的。有人可以向我解释一下吗？
==================== EDIT: Let's ask that another way:
==================== 编辑：让我们换一种方式问：
Date date = new Date();
Calendar c1 = Calendar.getInstance();
c1.setTime(date);
Calendar c2 = Calendar.getInstance();
c2.set(date.getYear(), (date.getMonth() - 1), date.getDay());
int day1 = c1.get(Calendar.DAY_OF_WEEK);
int day2 = c2.get(Calendar.DAY_OF_WEEK);
// day1 != day2 ---> I'd like to know - WHY?
So for now are dates as follows:
所以现在的日期如下：
date: Nov 5, 2013 4:27:02 PM
day1: 3
day2: 1
time: 1383665222638
timezone: Europe/Prague
采纳答案by Joni
This line does not do what you think it does:
这一行不会做你认为它做的事情：
c2.set(date.getYear(), (date.getMonth() - 1), date.getDay());
The deprecated methods in the Dateclass work like this:
Date类中已弃用的方法的工作方式如下：
getYear()returns year - 1900, so that for example 1986 is returned as 86, and 2013 is returned as 113.getMonth()returns month - 1, so November is returned as 10. Subtracting 1 gives you October.getDay()returns the day of the week; Tuesday is returned as 2.
getYear()返回年份 - 1900，例如 1986 返回为 86，2013 返回为 113。getMonth()返回月份 - 1，因此 11 月返回为 10。减去 1 得出 10 月。getDay()返回星期几；星期二返回为 2。
So, given your date, you are setting the calendar's date to Oct 2 year 113. The correct use of the API would be:
因此，根据您的日期，您将日历的日期设置为 113 年 10 月 2 日。 API 的正确用法是：
c2.set(1900+date.getYear(), date.getMonth(), date.getDate());
回答by Ruchira Gayan Ranaweera
There is no issue in this
这没有问题
Calendar c = Calendar.getInstance();
c.setTime(new Date());
c.set(2013, (12 - 1), 05);
int dayOfWeek = c.get(Calendar.DAY_OF_WEEK);
If you are trying to do some thing like following will deprecated since you are using Date.
如果您尝试执行以下操作，则不推荐使用，因为您使用的是 Date。
c.set(new Date().getYear(), (new Date().getMonth() - 1), new Date().getDate());
//don't use `java.util.Date` here since there can be differences
java.util.Calendarvalues over java.util.Date
java.util.Calendar价值超过 java.util.Date
回答by jbx
Your approach will get a bit hairy especially because of timezones and daylight savings. A lot of the Datemethods were deprecated because they were confusing to work with.
The approach I like to use is this:
您的方法会有点麻烦，尤其是因为时区和夏令时。许多Date方法已被弃用，因为它们使用起来令人困惑。我喜欢使用的方法是这样的：
Calendar c = Calendar.getInstance();
c.setTimeInMillis(date.getTime());
//get the same day but previous month
c.add(Calendar.MONTH, -1);
That way I let the Calendardo the calculation.
这样我就让Calendar计算。
