在继续使用Java中的另一个线程之前，如何等待线程做某事？

Question

I have a graphical user interface named Welcome, created with JFormDesigner. I want to wait until a button is clicked on that form before continuing my application.

I am doing this using synchronized and instancing the GUI as the object to wait for.

synchronized(new Welcome()) {
    wait();
}

Inside of my GUI, I have a start button which when clicked runs this:

public void startScript() {
    synchronized(this) {
        notify();
    }

    // Close the GUI
    dispose();
}

The GUI successfully loads however, I get this error:

Exception in thread "main" java.lang.IllegalMonitorStateException at java.lang.Object.wait(Native Method) at java.lang.Object.wait(Object.java:502) at dtohh.main.Main.(Main.java:20) at dtohh.tests.Tests.main(Tests.java:11)

before I can even press the Start button on my GUI. When I then press the button, the script ends and does nothing more.

I added this to test if it was working correctly:

synchronized(new Welcome()) {
    wait();
}

System.out.println("Test");

But after the button is pressed, the application exits and the output is not shown. How can I wait for the button to be pressed correctly?

Answer 1

I managed to figure it out, I need to wait on the Welcome.class instance and notify using this on the second thread.

Main thread:

Welcome gui = new Welcome();
syncronized(gui) { gui.wait(); }

Second thread:

private void onStart() {
    syncronized(this) { notifyAll(); }
    dispose();
}