multithreading - Java EventQueue. Why should everything be in invokelater method?

Question

in the book that i'm reading, every example of GUI with multithreading has something like that:

public static void main(String[] args) throws Exception
{
    EventQueue.invokeLater(new Runnable()
    {
        public void run()
        {
            JFrame frame = new SomeKindOfFrame();
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            frame.setVisible(true);
        }
    });
}

(i mean EventQueue). but isn't the code automatically executed in the main (EDT) thread?

Answer 1

The main thread isn't the same as the EDT. If you add System.out.println(Thread.currentThread().getName() you'll see it print out main within main() and AWT-EventQueue-0 when within the run() method of the Runnable.

Here is a discussion of the history of the single threaded rule in Swing that might help make things clearer.