java 如何只比较Java日期中的一天？
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How to compare just the day in a java date?
提问by Toran Billups
I'm trying to do a simple date comparison between yesterday and today
我正在尝试在昨天和今天之间做一个简单的日期比较
if (yesterday.before(today)) {
...
}
The issue is that with the before method I will eval to true even if it's just a few seconds difference. How might I compare just the day (because I only want to eval this to true if it was the previous day (minutes/seconds should be ignored)
问题是，使用 before 方法，即使只有几秒钟的差异，我也会评估为 true。我如何只比较当天（因为如果是前一天，我只想将其评估为真（应忽略分/秒）
Thank you in advance
先感谢您
回答by Praveen Lobo
回答by s106mo
If you don't want to use a 3rd party library implement a method like this:
如果您不想使用第 3 方库，请实现如下方法：
public boolean before(Calendar yesterday, Calendar today) {
if(yesterday == today) return false;
if(yesterday == null || today == null) return false;
return yesterday.get(Calendar.YEAR) < today.get(Calendar.YEAR) ? true :
yesterday.get(Calendar.YEAR) == today.get(Calendar.YEAR) && yesterday.get(Calendar.DAY_OF_YEAR) < today.get(Calendar.DAY_OF_YEAR);
}
回答by Don Roby
If you're up to adding a library that handles dates better than the standard Java libraries, you might want to look at Joda.
如果您要添加一个比标准 Java 库更好地处理日期的库，您可能需要查看Joda。
Using Joda, you can compute difference between days by:
使用 Joda，您可以通过以下方式计算天之间的差异：
Days d = Days.daysBetween(startDate, endDate);
int days = d.getDays();
where startDateand endDateare the Joda version of dates, DateTime(actually a superclass of that).
其中startDate和endDate是 Joda 版本的日期，DateTime（实际上是它的超类）。
Converting Java Dateobjects to Joda DateTimeobjects can be done by a constructor call:
可以通过构造函数调用将 JavaDate对象转换为 JodaDateTime对象：
DateTime dateTime = new DateTime(javaDate);
Adding this library may be overkill for this specific problem, but if you deal with date and time manipulation a lot, the library is definitely worth it.
添加这个库对于这个特定的问题可能有点矫枉过正，但如果你经常处理日期和时间操作，那么这个库绝对值得。
回答by pdresselhaus
If you want to stick to Dateyou could temporarily lower your current date by one day. If before()still leads to the same result you have a timespan of at least one day.
如果你想坚持，Date你可以暂时将当前日期减少一天。如果before()仍然导致相同的结果，则您的时间跨度至少为一天。
final static long DAY_MILLIS = 86400000;
Date d1 = new Date(2011, 06, 18);
Date d2 = new Date(2011, 06, 16);
Date temp = new Date(d1.getTime() - DAY_MILLIS);
if (temp.before(d2))
// Do stuff
}
Please note I used a deprecated constructor but it should do the job.
请注意，我使用了一个已弃用的构造函数，但它应该可以完成这项工作。
