Swing EDT and UIManager Initialization Question

We all know you are supposed to only interact with Swing GUI components on the event dispatch thread (EDT). Your main method might look like this:

public static void main(String[] args) {
  SwingUtilities.invokeLater(new Runnable() {
    public void run() {
      createAndShowGui();
    }
  });
}

But what about the first time you call UIManager.setLookAndFeel(...)? Does this one-time action have to go on the EDT?

Sun’s own examples are inconsistent.

First example:

public static void main(String[] args) {
  //Schedule a job for the event dispatch thread:
  //creating and showing this application's GUI.
  javax.swing.SwingUtilities.invokeLater(new Runnable() {
    public void run() {
      createAndShowGUI();
    }
  });
}

private static void createAndShowGUI() {
  //Set the look and feel.
  initLookAndFeel();
  ...
}

private static void initLookAndFeel() {
  ....
  UIManager.setLookAndFeel(lookAndFeel);
  ...
}

So you see, in that example, they are careful to set the look and feel on the EDT.

But here is another example from the same web site:

public static void main(String[] args) {
  try {
    UIManager.setLookAndFeel("javax.swing.plaf.metal.MetalLookAndFeel");
  } catch (...) {
    ...
  }

  //Schedule a job for the event-dispatching thread:
  //creating and showing this application's GUI.
  javax.swing.SwingUtilities.invokeLater(new Runnable() {
    public void run() {
      createAndShowGUI();
    }
  });
}

I assume the second example is wrong. I believe you might be able to get away with it, maybe even thousands of times, but perhaps once in awhile you might see some weird threading issue or memory visibility problem. ???

What is the correct answer?

Posted on Tuesday, October 23rd, 2007 at 10:32 am in Java.