Re: Thread stuck in state NEW?

From:
SadRed <cardinal_ring@yahoo.co.jp>
Newsgroups:
comp.lang.java.programmer
Date:
23 May 2007 19:13:21 -0700
Message-ID:
<1179972801.632953.115150@d30g2000prg.googlegroups.com>
On May 24, 11:03 am, Daniel Pitts <googlegrou...@coloraura.com> wrote:

On May 23, 6:48 pm, Mark Space <marksp...@sbc.global.net> wrote:

Hi all, I was planning on doing some swing testing, but ran into a
thread issue instead. The problem is a small anonymous thread class I
create stays stuck in state NEW, even though it apparently runs an
completes.

package crazythreads;

import javax.swing.JOptionPane;

public class Main
{
     public static void main(String[] args)
     {
         Main test = new Main();
         System.out.println( test.thready() );
     }

     private String thready()
     {
         String result = null;
         Thread t = new Thread(){
             public void run() {
                 //result = (String)JOptionPane.showInputDialog(
                 JOptionPane.showInputDialog(
                         null,"Enter a random string:");
             }
         };
         javax.swing.SwingUtilities.invokeLater(t);
         try {
             while( t.getState() == Thread.State.NEW ) // STUCK HERE
                 Thread.sleep(100);
             while( t.getState() != Thread.State.TERMINATED)
                 t.join(100);
         } catch( Exception ex) {ex.printStackTrace();}
         if( result == null )
             return "No result.";
         return result;
     }

}

The debugger shows the main thread stepping through the while loop at
the comment STUCK HERE. The Thread, t, does run: I see it's dialog box
come up, I enter a value and press OK. So it should at some point be in
  one of the running states (probably blocked on IO). Before adding the
while loops, the main thread did not wait (at the t.join()) and just
proceeded on to return "No Result." We can ignore the issues with
result for now. ;-)

Anyone got any ideas? Being stuck in state NEW just confuses the heck
out of me. Did I blow a conditional test somewhere?


invokeLater is NOT what you want to do for Thread

invokeLater passes a Runnable object to be executed on the
EventDispatchThread.

Thread happens to implement Runnable, so your code will get called on
the EDT, but your thread object itself doesn't know or care about the
EDT vs its self.

Generally, if you are updating the GUI, you want to create a Runnable
(not thread) and use invokeLater, or invokeAndWait.

Although, I believe the JOptionPane calls are safe to call from any
thread, so you don't need to create a new thread to do so. Double
check the API doc before you take my word on that.


Daniel Pitts is right.
OP's Thread t is never run, so it remains NEW state indefinitely. A
thread that involeLater() would make, in which the JOptionPane is
instantiated, is completely different from the Thread t of the Main
class.

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