Is JCheckBox.isSelected() thread safe?

Question

I am currently refactoring an application I made to be thread safe.

I have a JCheckBox that I need to check. This JCheckBox is referenced throughout the program in various different threads.

Can I simply call checkbox.isSelected() or do I have to make this call using invokeLater?

I'm finding it difficult to understand concurrency in general, but I'm getting there slowly but surely. If this is a stupid question, please tell me why so I can better my understanding.

Thank you.

Answer 1

No, it's not thread safe. Swing generally is not thread safe. You need to use invokeLater. On the other hand, you can make the current thread wait until the task ininvokeLater finishes:

private boolean isSelected(final AbstractButton button) {
    if (SwingUtilities.isEventDispatchThread()) {
        // a shortcut so the AWT thread won't wait for itself
        return button.isSelected();
    }
    final AtomicBoolean isSelected = new AtomicBoolean();
    final CountDownLatch latch = new CountDownLatch(1);
    SwingUtilities.invokeLater(() -> {
        try {
            isSelected.set(button.isSelected());
        } finally {
            latch.countDown();
        }
    });
    try {
        latch.await();
    } catch (InterruptedException e) {
        throw new RuntimeException(e);
    }
    return isSelected.get();
}