Re: Thread.wait()

Lew <lew@lewscanon.nospam>
Wed, 13 Jun 2007 12:49:31 -0400
R. Vince wrote:

I'm struggling getting my head around this for some reason today. I'm not
referring to things correctly i n my code, with respect to the threads -- I
must be misunderstanding you Gordon, because I am getting and
IllegalMonitorStateException when I call notify on the runnable, from, what
I believe, is the class that owns the Runnable, yes?

Not relevant. The question for notify() is "who owns the monitor?" It's got
nothing to do with Runnable.

Exception in thread "AWT-EventQueue-0"
java.lang.IllegalMonitorStateException: current thread not owner
        at java.lang.Object.notify(Native Method)

public class SmartResponder {
    public Runnable studyinteractive;

Why not provide an /actual/ SSCCE?

    public void doResponseStudy() {
        studyinteractive = new Runnable(){
            public void run(){
    public void study(){
                    synchronized(this) {
                }catch(InterruptedException interruptedexception) { }
    public boolean getGoBack(){ //pared down here, b is actually a long
conditional, not merely what is shown
        boolean b= arrayList.size()>0;
        if(!b )
            studyinteractive.notify(); //// <-----------line 411
        return b;

Have you considered reading the Javadocs?

Wakes up a single thread that is waiting on this object's monitor.

This object being the one on whom nofify() is called, i.e., "studyinteractive"
in your case. Since "studyinteractive" doesn't own the monitor, it isn't able
to do that.

Think of "notify()" as a kind of random release() call, "I'm releasing my
monitor now!" sent to an arbitrary Thread.

Your use of the "studyinteractive" variable (which, btw, should be spelled by
convention with initial capital letters to kick off the word parts, i.e.,
"studyInteractive") confuses me, and probably the JVM, too. Your Runnable
seems to want to be the one running getGoBack() in its own Thread, yet you
call notify() not through 'this' but through the instance variable.

"notify()" is meant to be called from 'this'.

This method should only be called by a thread that is the owner of this object's monitor.

Ain't the Javadocs wonderful?


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