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From "David Smiley (JIRA)" <>
Subject [jira] Updated: (LUCENE-1653) Change DateTools to not create a Calendar in every call to dateToString or timeToString
Date Tue, 07 Jul 2009 23:01:14 GMT


David Smiley updated LUCENE-1653:

    Attachment: cleanerDateTools.patch

Applying the attached patch shows the improvements to that I think should be
done.  All logic that does anything at all is moved to instance methods of the inner class
Resolution.  I argue this is more object-oriented.

1. In cases where Resolution is an argument to the method, I can simply invoke the appropriate
call on the Resolution object.  Formerly there was a big branch if/else.
2. Instead of "synchronized" being used seemingly everywhere, synchronized is used to sync
on the object that is not threadsafe, be it a DateFormat or Calendar instance.
3. Since different DateFormat and Calendar instances are created per-Resolution, there is
now less lock contention since threads using different resolutions will not use the same locks.
4. The old implementation of timeToString rounded the time before formatting it.  That's unnecessary
since the format only includes the resolution desired.
5.round() now uses a switch statement that benefits from fall-through (no break).

Another debatable improvement is putting the resolution instances into an array indexed by
format length.  This would mean I could remove big-ish switch in lookupResolutionByLength()
and avoid the length constants there... but I don't think that's a big deal.

> Change DateTools to not create a Calendar in every call to dateToString or timeToString
> ---------------------------------------------------------------------------------------
>                 Key: LUCENE-1653
>                 URL:
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Other
>            Reporter: Shai Erera
>            Assignee: Mark Miller
>            Priority: Minor
>             Fix For: 2.9
>         Attachments: cleanerDateTools.patch, LUCENE-1653.patch, LUCENE-1653.patch
> DateTools creates a Calendar instance on every call to dateToString and timeToString.
> # timeToString calls Calendar.getInstance on every call.
> # dateToString calls timeToString(date.getTime()), which then instantiates a new Date().
I think we should change the order of the calls, or not have each call the other.
> # round(), which is called from timeToString (after creating a Calendar instance) creates
another (!) Calendar instance ...
> Seems that if we synchronize the methods and create the Calendar instance once (static),
it should solve it.

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