Question

I’m trying to write some GUI and integration tests using JUnit and FEST.
Here is what I have:

@Before
public void setUp(){
    try{
        program.main(args);
        robot.wait(30000);    //gives IllegalMonitorStateException
        Thread.sleep(30000);  //no Exception occurs here
    } catch (Exception e){
        e.printStackTrace();
    }
}

robot and args are already initialized.

Why do I get such an exception when I call wait? Why I don’t get the same exception when I call sleep?

Answer 1

You’re calling Object.wait() – which is not the same as Thread.sleep(). In particular:

• wait() requires that you already own the monitor on the object you call it on
• wait() allows the thread to be notified (via Object.notify/notifyAll) and wake up early; Thread.sleep() would require the thread to be interrupted.