tag:blogger.com,1999:blog-32236815094617522082024-09-29T00:13:01.234-04:00memymoJust my thoughtsmemymohttp://www.blogger.com/profile/17607526342805648053noreply@blogger.comBlogger1125tag:blogger.com,1999:blog-3223681509461752208.post-79978205463713147522010-08-03T11:46:00.002-04:002013-03-06T13:57:59.920-05:00java date compare<div dir="ltr" style="text-align: left;" trbidi="on">
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if you ever tried to compare java dates, you will get unexpected results if you do not consider time component of java date, for example if you try to<b> compare</b> 2010-08-03 with 2010-08-01,<br />
then you can see that date1 is greater and the difference is 2 day, but if you write java code as below.<br />
<pre class="brush: java">
import java.util.Calendar;
public class TestDateCompare {
private final long MILLSECS_PER_DAY = 24 * 60 * 60 * 1000;
public TestDateCompare() throws InterruptedException{
Calendar today = Calendar.getInstance();
// Add 2 second delay so we can have difference between 2 dates
Thread.sleep(2000);
Calendar yesterday = Calendar.getInstance();
//Substract 2 days from today
yesterday.add(Calendar.DATE, -2);
long numOfDaysDifference = ( today.getTime().getTime() - yesterday.getTime().getTime() )/ MILLSECS_PER_DAY;
//This should print output as 2, but it prints output as 1,
System.out.println("Num of days difference " + numOfDaysDifference);
System.out.println("Yesterday " + yesterday.getTime());
System.out.println("Today " + today.getTime());
}
public static void main(String[] args) throws InterruptedException {
new TestDateCompare();
}
}
</pre>
<div>
The out put of this class is</div>
<div style="border: 1px dotted #ccc; color: green; overflow-x: auto; overflow: auto; padding: 5px 5px 5px 7px;">
<div>
Num of days difference 1</div>
<div>
Yesterday Sun Aug 01 11:31:43 EDT 2010</div>
<div>
Today Tue Aug 03 11:31:41 EDT 2010</div>
</div>
<div>
As you can see there is 2 seconds difference, which throws the calculation off, so to make this work add following lines of code before doing date calculation</div>
<div style="border: 1px dotted #ccc; color: blue; overflow-x: auto; overflow: auto; padding: 5px 5px 5px 7px;">
<div>
today.set(Calendar.HOUR, 0);</div>
<div>
today.set(Calendar.MINUTE, 0);</div>
<div>
today.set(Calendar.SECOND, 0);</div>
<div>
today.set(Calendar.MILLISECOND, 0);</div>
<div>
</div>
<div>
yesterday.set(Calendar.HOUR, 0);</div>
<div>
yesterday.set(Calendar.MINUTE, 0);</div>
<div>
yesterday.set(Calendar.SECOND, 0);</div>
<div>
yesterday.set(Calendar.MILLISECOND, 0);</div>
</div>
Do not forget millisecond also, as it may throw off the calculation<br />
After this change the output is as below<br />
<br />
<div style="border: 1px dotted #ccc; color: green; overflow-x: auto; overflow: auto; padding: 5px 5px 5px 7px;">
Num of days difference 2<br />
Yesterday Sun Aug 01 00:00:00 EDT 2010<br />
Today Tue Aug 03 00:00:00 EDT 2010</div>
<br />
There are many other alternatives, like using <a href="http://mindprod.com/jgloss/bigdate.html" target="_blank" title="BigDate">BigDate</a> or <a href="http://joda-time.sourceforge.net/" target="_blank" title="Joda-Time">joda-time</a>,<br />
If you have anymore solutions, please feel free to add to this list</div>
</div>memymohttp://www.blogger.com/profile/17607526342805648053noreply@blogger.com0