Groups > comp.lang.java.programmer > #30966

Concurrency question?

From	Knute Johnson <nospam@rabbitbrush.frazmtn.com>
Newsgroups	comp.lang.java.programmer
Subject	Concurrency question?
Date	2015-01-31 10:34 -0800
Organization	A noiseless patient Spider
Message-ID	<maj766$qjf$1@dont-email.me> (permalink)

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So I have a Map<Integer,String> but it could be a List or an Array, 
shouldn't make any difference.  Access to the Map is controlled by a 
ReadWriteLock.  Several threads read values from the Map and one thread 
can change values or write to or remove key/value pairs from the Map. 
The thread that writes new values to the Map is the EDT, in a 
DocumentListener.  One of the reading threads is time consuming and if 
that thread has the read lock the EDT blocks until it can obtain the 
write lock.  That can generate noticeable delays in data entry through 
the GUI.

Since data entry is slow it doesn't matter much if the data entry 
changes are available during the time period that the time consuming 
thread is reading the Map.  However to ensure that I have current data 
at some point any read access of the Map must be controlled by a read lock.

I needed a way to make the time consuming thread not need to hold the 
read lock for the entire time.  My solution was to acquire the read lock 
and create a List of values from the Map and return the read lock, this 
is very quick.  Then I iterate through the List to perform the time 
consuming task.

I know that it is possible that the GUI could change the Map while the 
time consuming thread is running.  That isn't critical as the data would 
be current the next time the time consuming thread ran.  The reference 
to the List goes out of scope when the time consuming thread completes. 
  Any values that were in the List that were no longer in the Map should 
be available for garbage collection.

Do you see any holes in my logic?  Any suggestions?

Thanks,

Knute...

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Thread

Concurrency question? Knute Johnson <nospam@rabbitbrush.frazmtn.com> - 2015-01-31 10:34 -0800
  Re: Concurrency question? Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-01-31 14:04 -0500
    Re: Concurrency question? Knute Johnson <nospam@rabbitbrush.frazmtn.com> - 2015-01-31 11:23 -0800
  Re: Concurrency question? Arne Vajhøj <arne@vajhoej.dk> - 2015-01-31 14:12 -0500
    Re: Concurrency question? Knute Johnson <nospam@rabbitbrush.frazmtn.com> - 2015-01-31 11:33 -0800
  Re: Concurrency question? v_borchert@despammed.com (Volker Borchert) - 2015-01-31 19:20 +0000
    Re: Concurrency question? Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-01-31 15:42 -0500
      Re: Concurrency question? Knute Johnson <eternal@knutejohnson.com> - 2015-01-31 19:51 -0800
        Re: Concurrency question? Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-02-01 09:24 -0500
  Re: Concurrency question? Kevin McMurtrie <mcmurtrie@pixelmemory.us> - 2015-01-31 22:59 -0800
    Re: Concurrency question? Arne Vajhøj <arne@vajhoej.dk> - 2015-02-01 12:55 -0500
      Re: Concurrency question? Silvio <silvio@internet.com> - 2015-02-01 22:19 +0100
      Re: Concurrency question? Kevin McMurtrie <mcmurtrie@pixelmemory.us> - 2015-02-06 22:29 -0800
        Re: Concurrency question? Knute Johnson <eternal@knutejohnson.com> - 2015-02-07 10:14 -0800
        Re: Concurrency question? Robert Klemme <shortcutter@googlemail.com> - 2015-02-08 19:33 +0100
  Re: Concurrency question? olupot douglas <olupotd3@gmail.com> - 2015-02-07 01:06 -0800
  Re: Concurrency question? Haddock <ffm2002@web.de> - 2015-02-16 06:32 -0800

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