SimpleDateFormat的返回解析过程中错误的日期值 [英] SimpleDateFormat returns wrong date value during parse
问题描述
我米面临一个问题：我想获得GMT时间的当前时间长。
我米用下面的code下面给出：
I m facing a problem:I want to get current time of GMT TimeZone in long. I m using the following code as given below:
TimeZone timeZoneGmt = TimeZone.getTimeZone("GMT");
long gmtCurrentTime = getCurrentTimeInSpecificTimeZone(timeZoneGmt);
public static long getCurrentTimeInSpecificTimeZone(TimeZone timeZone) {
Calendar cal = Calendar.getInstance();
cal.setTimeZone(timeZone);
long finalValue = 0;
SimpleDateFormat sdf = new SimpleDateFormat(
"MMM dd yyyy hh:mm:ss:SSSaaa");
sdf.setTimeZone(timeZone);
Date finalDate = null;
String date = sdf.format(cal.getTime());
try {
finalDate = sdf.parse(date);
} catch (ParseException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
finalValue = finalDate.getTime();
return finalValue;
}
正如给出，上述方法
而格式化结果字符串日期= sdf.format（cal.getTime（））;
我m到处当前时间在格林尼治标准时间，但像我一样按照code解析：
As given in, above method
while formatting
String date = sdf.format(cal.getTime());
I m getting correct current time in GMT but as i do parsing by following code:
finalDate = sdf.parse（日期）;
日期接到了当前GMT时间改为15时35分16秒IST 2013这是我的系统当前时间。
Date got changed from current GMT time to 15:35:16 IST 2013 that is current time of my system.
我试图日历以及以另一种方式：
TimeZone timeZoneGmt=TimeZone.get("GMT");
Calendar calGmt = Calendar.getInstance();
calGmt.setTimeZone(timeZoneGmt);
long finalGmtValue = 0;
finalGmtValue = calGmt.getTimeInMillis();
System.out.println("Date......" + calGmt.getTime());
但仍然得到日期，我的系统周四1月23日15点58分16秒IST 2014年没有得到GMT当前时间的当前时间。
but still getting date as current time of my System Thu Jan 23 15:58:16 IST 2014 Not getting GMT current time.
推荐答案
您误解了如何日期的作品。 A 日期没有的有无的时区 - 如果你使用与Date.toString（）你的总是的看到默认的时区。在日期长期价值纯粹是自Unix纪元的毫秒数。它没有时区或日历系统的任何概念
You've misunderstood how Date works. A Date doesn't have a time zone - if you use Date.toString() you'll always see the default time zone. The long value in a Date is purely the number of milliseconds since the Unix epoch: it doesn't have any concept of time zone or calendar system.
如果你想重新present在特定的时间段和日历的日期和时间，使用日历代替 - 但获取当前日期和时间作为一项长期的，你可以只用 System.currentTimeMillis的（），而这又不会有什么做的系统时区。
If you want to represent a date and time in a particular time zone and calendar, use Calendar instead - but for getting "the current date and time as a long" you can just use System.currentTimeMillis(), which again does not have anything to do with the system time zone.
此外，即使你的没有的想要做的操作就是这样，你不应该使用字符串转换进行。你不是的概念的执行任何字符串转换，那么为什么他们介绍？
Additionally, even if you did want to do manipulation like this, you shouldn't be using string conversions. You're not conceptually performing any string conversions, so why introduce them?
如果你的目的是要显示（字符串）在一个特定的时区的当前日期和时间，你应该使用这样的：
If your aim is to display (as a string) the current date and time in a particular time zone, you should just use something like:
Date date = new Date(); // This will use the current time
SimpleDateFormat format = new SimpleDateFormat(...); // Pattern and locale
format.setTimeZone(zone); // The zone you want to display in
String formattedText = format.format(date);
当日期和时间API的工作 - 尤其是坏的类似于Java 日历 / 日期 API - 这是非常的重要的，你明白到底是什么在你的系统重新presents每个值。
When working with date and time APIs - particularly bad ones like the Java Calendar/Date API - it's very important that you understand exactly what each value in your system represents.
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