Re: Thread stuck in state NEW?

Eric Sosman <esosman@acm-dot-org.invalid>
Wed, 23 May 2007 22:11:12 -0400
Mark Space 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

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(
                        null,"Enter a random string:");
        try {
            while( t.getState() == Thread.State.NEW ) // STUCK HERE
            while( t.getState() != Thread.State.TERMINATED)
        } 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?

     The thread `t' never starts at all, hence remains forever
in state NEW. The argument to invokeLater() is not a Thread
per se, but a Runnable (Thread implements Runnable, which is
why the code compiles). invokeLater() arranges for the run()
method of its Runnable to be called by the Event Dispatching
Thread, and its the EDT that displays your JOptionPane. But
the "thread-ness" of t is never used; only its "runnable-ness"
comes into play -- and on a different thread, at that.

     What are you trying to accomplish with this JOptionPane?
Yes, you said to "ignore the issues with result for now," but
I suspect those very issues are central to finding the right

Eric Sosman

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