How to remove Focus Listener from the JFormattedTextField, in my example of the code?

I am having trouble removing focus listener after adding it to JFormattedTextField. I read about removeFocusListener, but couldn't find examples how to use it. It seems easy enough but no matter what I try it wouldn't work.

Here's a relevant part of the code, where I add the listener, do what I need with it, and where I want to remove it:

private JFormattedTextField heightArea;
heightArea.addFocusListener(new FocusListener() {
    @Override
    public void focusGained(FocusEvent e) {
        heightArea.setText(getHeight(widthArea));
    }

    @Override
    public void focusLost(FocusEvent e) {
    }
});
// From here on I want to remove this listener.

I would try things like:

heightArea.removeFocusListener(new FocusListener() );

or

heightArea.removeFocusListener(heightArea.FocusListener() );

But of course it didn't work. I am not really sure what I should pass to the removeFocusListener from heightArea to remove that focus listener.

Sorry for my inexperience, hopefully you can point me towards the right direction, so I could understand what I am doing wrong.

Any help is appreciated, thank you very much.

Create a class MyFocusListener and declare a class level variable of the same type. Something like this

MyFocusListener myFocusListener = new MyFocusListener();

    class MyFocusListener implements FocusListener {

        @Override
        public void focusGained(FocusEvent e) {
           // add your logic here
        }

        @Override
        public void focusLost(FocusEvent e) {

        }

    }

Then add/remove this listener to your textfield

heightArea.addFocusListener(myFocusListener);
heightArea.removeFocusListener(myFocusListener);