@Override
	public void propertyChange(PropertyChangeEvent event) {
		super.propertyChange(event);
		if (event.getProperty().equals(FieldEditor.VALUE)) {
			checkState();
		}
		if (event.getSource() == enabledField) {
			if (previousEnabledString == null) {
				previousEnabledString = event.getOldValue().toString();
			}
			currentEnabledString = event.getNewValue().toString();
		}
		else if (event.getSource() == portField) {
			if (previousPortString == null) {
				previousPortString = event.getOldValue().toString();
			}
			currentPortString = event.getNewValue().toString();
		}
	}
This class represents a preference page that
is contributed to the Preferences dialog. By 
subclassing <samp>FieldEditorPreferencePage</samp>, we
can use the field support built into JFace that allows
us to create a page that is small and knows how to 
save, restore and apply itself.
<p>
This page is used to modify preferences only. They
are stored in the preference store that belongs to
the main plug-in class. That way, preferences can
be accessed directly via the preference store.
GhidraBuild/EclipsePlugins/GhidraDev/GhidraDevPlugin/src/main/java/ghidradev/ghidrascripteditor/preferences/GhidraScriptEditorPreferencePage.java