Strange nop(?) code in java.awt.Dialog

Question

Can anyone give some explanation for the following code?
private void hideAndDisposeHandler() {
    if (keepBlocking) {
        synchronized (getTreeLock()) {
            keepBlocking = false;
            EventQueue.invokeLater(new Runnable(){ public void run() {} });
            //what was that for???
            getTreeLock().notifyAll();
} It seems some strange hacks are going on out there.
Thanks,
Dimitris

Answer 1

It's also possible that the Runnable is a fence that
prevents AWTEvents from being coalesced into one
another from opposite sides. Was this from src.zip, or
did you decompile the class file? Is the comment
theirs, or yours? I would have expected to see a
comment about it in their code.I looked at the java src from the src.zip. You can also get the real java src with the C code to build your own JRE, but it's the same as the code they include with the JDK.
This comment is mine as they don't provide it (though they should, what they are doing is not obvious). It's just a guess, but from the code I'd say that it' the goal. The invokeLater function causes a chain reaction that causes all currently pending events to be executed. Normally, you would call this from another thread, and it would be executed non-sync with your current thread. If you execute it from the event queue thread then it seems that all events are flushed and then your functionality is run.
The event queue system has it's good and bad points, it's easy to start coding, but you really can't do a lot of custom processing of events. Modal dialogs are one thing that they had to do a strange hack to get to work correctly. Even then, they don't always work correctly. Multiple modal dialogs tend to mess up.