线程“ AWT-EventQueue-0”中的异常java.lang.Object.notify上的java.lang.IllegalMonitorStateException（本机方法）

Question

What I'm trying to do:

Launch a window to request parameters

What I've tried:

1. If I remove the vp.wait() , the window disappears.
2. If I remove notify() , the program doesn`t wait.

Here's my code:

public static void main(String[] args) throws InterruptedException{
    if(args.length==0){
        ParamsWind vp = new ParamsWind();
        vp.setVisible(true);
        synchronized (vp){
             try {
                vp.wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
 .....


public class ParamsWind extends JDialog {
  ...
  public ParamsWind() 
    ....
       //Create Ok Button and program Action Listener
    Button ok = new Button("OK");
    ...
    ok.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent arg0) { 

            if(f.getText().equals("") || r.getText().equals("")){
                ErrorWind verr = new ErrorWind();
                verr.setVisible(true);
            }
            notify();

Answer 1

Well here's the problem, in actionPerformed .

notify();

You're doing that without a synchronized block, so the thread doesn't own the monitor for this ... hence the exception.

However, you don't just want a synchronized block, because you're actually calling notify() on the wrong object. You want to use the ParamsWind :

synchronized(ParamsWind.this) {
    ParamsWind.this.notify();
}

It's not clear to me that using wait() and notify() is really what you want here - or that you won't end up with a race condition - but those are the immediate problems with what you're doing.