Question

I have a program that detects when certain machines are online and creates a button with a green “online” icon to show this. I want to add the functionality to check periodically if this machine is still online, and if it’s not, change the icon to the “offline” icon that I’ve already defined.

Answer 1

I know how to set the icon, however I can’t figure out a way to do it
once the button has already been displayed

probably you have issues with Concurency in Swing, that means that all Swing code must be done on EDT

then you have to wrap myButton.setIcon(myIcon) to the invokeLater(), for example

SwingUtilities.invokeLater(new Runnable() {

    @Override
    public void run() {
        myButton.setIcon(myIcon);
    }
});