Re: How to change JPanels?

From:
Ian Shef <invalid@avoiding.spam>
Newsgroups:
comp.lang.java.help
Date:
Thu, 17 Feb 2011 19:51:25 GMT
Message-ID:
<Xns9E8F82CA35852vaj4088ianshef@138.125.254.103>
Eric <e.d.programmer@gmail.com> wrote in news:25380f9b-1d8e-4515-9bb4-
fd8e5d87d828@r19g2000prm.googlegroups.com:

<snip>

Either I'm misunderstanding it or we're all saying the same thing 2
different ways so correct me if I'm wrong. Which of these statements
is wrong?
1) A Java program runs in a thread. If you want the program to do 2
things at once you start a new thread.

OK

2) If you run my test program from my last post and click the menu
option it starts a new worker thread. That worker thread executes a
done() method as EDT.

I don't know, I no longer have the program. However, only the EDT can
execute a method as EDT.

3) The menu option event takes 3 seconds to process. You can click it
again before it finishes and have it running 2 new concurrent EDT
threads.

No. At any instant, a Java program has at most one EDT.

4) While the menu item worker is running, the main window program is
still running in a thread listening for new events. It's thread is
also EDT.

Your wording is unclear to me but, at any instant, a Java program has at
most one EDT.

The following program may be instructive if you read through its output.
[Remember too that Swing makes use of AWT.]

public class EdtExperiment2 {

  static void msg(Object ob) { System.out.println(ob) ; }

  static void dumpThreads() {
    for (Thread t : Thread.getAllStackTraces().keySet()) msg(t) ;
    msg("========") ;
  }

  public static void main(String[] args) {
    dumpThreads() ;
    javax.swing.SwingUtilities.invokeLater( new Runnable() {
      public void run() {
        msg("EDT is " + Thread.currentThread()) ;
        msg("========") ;
      }
    }) ;
    dumpThreads() ;
  }
}

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