Re: updating an ImageIcon's backing BufferedImage content from multiple threads

Knute Johnson <>
Sun, 05 Apr 2009 21:53:07 -0700
John B. Matthews wrote:

In article
<>, wrote:

On Apr 6, 12:48 am, Lew <> wrote:

Knute Johnson wrote:


All this is fascinating :)

Indeed. I often turn to the Memory Consistency Properties summary found
in java.util.concurrent, noting "The results of a write by one thread
are guaranteed to be visible to a read by another thread only if the
write operation happens-before the read operation. [...] A call to start
on a thread happens-before any action in the started thread":


The latter condition can be met by having the buffer-modifying thread
call java.awt.EventQueue.invokeLater(), which runs its argument
asynchronously on the EDT:


I believe the notification sent by javax.swing.Timer also runs on the
EDT, thus satisfying the same requirement:


Often, modifying the buffer is the more time consuming operation, while
drawing the buffer's contents can proceed quickly without congesting the


Do you think that a thread enqueueing(sp) an event on the EDT with
invokeLater() produces a happens before relationship with that thread
even though Thread.start() is not called? Could that same mechanism
work in calls to repaint()?


Knute Johnson
email s/nospam/knute2009/

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