Java Foundation Classes in a Nutshell

TheEvent Dispatch Thread

For efficiency reasons, Swing components are not designed to be thread safe. This

means that Swing components should be manipulated by a single thread at a time.

The easiest way to ensure this is to do all your GUI manipulations from the event

dispatch thread. Every GUI application has an event dispatch thread: it is the

thr ead that waits for events to occur and then dispatches those events to the

appr opriate event handlers. All of your event listener methods are invoked by the

event dispatch thread, so any GUI manipulations you perfor m fr om an event lis-

tener are safe.

Ther e ar e times, however, when you need to update your UI in response to some

kind of external event, such as a response from a server that arrives in a separate

thr ead. To accommodate these situations, Swing provides two utility methods that

allow you ask the event dispatch thread to run arbitrary code. The methods are

SwingUtilities.invokeLater() and SwingUtilities.invokeAndWait().You pass

a

Runnable object to each method, and the run() method of this object is invoked

fr om the event thread.

invokeLater() retur ns right away, regardless of when the

run() method is invoked, while invokeAndWait() does not retur n until the run()

method has completed.

The

invokeLater() and invokeAndWait() methods do not run your Runnable

object right away. Instead, each method encapsulates the Runnable object within a ...