Chan != *

TroubleshootingGuide for Java SE 6DesktopTechnologies
http://java.sun.com/javase/6/webnotes/trouble/TSG-Desktop/TSG-Desktop.pdf

4.2.1 IncorrectThreading
Randomexceptions and painting problems are usually the result of incorrect threading usage of Swing. All access to Swing components, unless speciically noted in the javadoc,must be done on the event dispatch thread. This includes anymodels (TableModel, ListModel, and others) that are attached to Swing components.

The best way to check for bad usage of Swing is by way of an instrumented RepaintManager,as illustrated by the following code:

public class CheckThreadViolationRepaintManager extends RepaintManager {

    // it is recommended to pass the complete check
    private boolean completeCheck = true;

    public boolean isCompleteCheck() {
        return completeCheck;
    }

    public void setCompleteCheck(boolean completeCheck) {
        this.completeCheck = completeCheck;
    }

    public synchronized void addInvalidComponent(JComponent component) {
        checkThreadViolations(component);
        super.addInvalidComponent(component);
    }

    public void addDirtyRegion(JComponent component, int x, int y, int w, int h) {
        checkThreadViolations(component);
        super.addDirtyRegion(component, x, y, w, h);
    }

    private void checkThreadViolations(JComponent c) {

        if (!SwingUtilities.isEventDispatchThread() && (completeCheck || c.isShowing())) {

            Exception exception = new Exception();
            boolean repaint = false;
            boolean fromSwing = false;
            StackTraceElement[] stackTrace = exception.getStackTrace();

            for (StackTraceElement st : stackTrace) {
                if (repaint && st.getClassName().startsWith("javax.swing.")) {
                    fromSwing = true;
                }
                if ("repaint".equals(st.getMethodName())) {
                    repaint = true;
                }
            }

            if (repaint && !fromSwing) {
                //no problems here, since repaint() is thread safe
                return;
            }

            exception.printStackTrace();
        }
    }
}