Java System.currentTimeMillis() 对于给定日期？
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System.currentTimeMillis() for a given date?
提问by yanchenko
Since java.util.Date is mostly deprecated, what's the right way to get a timestamp for a given date, UTC time? The one that could be compared against System.currentTimeMillis().
由于 java.util.Date 大多已弃用，获取给定日期（UTC 时间）的时间戳的正确方法是什么？可以与System.currentTimeMillis().
采纳答案by David Sykes
Using the Calendarclass you can create a time stamp at a specific time in a specific timezone. Once you have that, you can then get the millisecond time stamp to compare with:
使用Calendar类，您可以在特定时区的特定时间创建时间戳。一旦你有了它，你就可以得到毫秒时间戳来比较：
Calendar cal = new GregorianCalendar();
cal.set(Calendar.DAY_OF_MONTH, 10);
// etc...
if (System.currentTimeMillis() < cal.getTimeInMillis()) {
// do your stuff
}
edit: changed to use more direct method to get time in milliseconds from Calendar instance. Thanks Outlaw Programmer
编辑：更改为使用更直接的方法从 Calendar 实例获取时间（以毫秒为单位）。感谢亡命之徒程序员
回答by TofuBeer
回答by Daniel Schneller
The "official" replacement for many things Date was used for is Calendar. Unfortunately it is rather clumsy and over-engineered. Your problem can be solved like this:
Date 用于许多事物的“官方”替代品是 Calendar。不幸的是，它相当笨拙且设计过度。你的问题可以这样解决：
long currentMillis = System.currentTimeMillis();
Date date = new Date(currentMillis);
Calendar calendar = Calendar.getInstance();
calendar.setTime(date);
long calendarMillis = calendar.getTimeInMillis();
assert currentMillis == calendarMillis;
Calendars can also be initialized in different ways, even one field at a time (hour, minute, second, etc.). Have a look at the Javadoc.
日历也可以用不同的方式初始化，甚至一次一个字段（小时、分钟、秒等）。看看Javadoc。
回答by jfpoilpret
Although I didn't try it myself, I believe you should take a look at the JODA-Time project (open source) if your project allows external libs. AFAIK, JODA time has contributed a lot to a new JSR (normally in Java7) on date/time.
虽然我自己没有尝试过，但我相信如果你的项目允许外部库，我相信你应该看看JODA-Time项目（开源）。AFAIK，JODA 时间对日期/时间的新 JSR（通常在 Java7 中）做出了很大贡献。
Many people claim JODA time is the solution to all java.util.Date/Calendar problems;-)
许多人声称 JODA 时间是所有 java.util.Date/Calendar 问题的解决方案；-)
Definitely worth a try.
绝对值得一试。
