Detecting JTextField “deselect” event

Question

Is there some way to detect if a JTextField is deselected, i.e. the field WAS selected but now you have selected something else. The reason why I want to do this is because

Answer 1

At first though use a FocusAdapter and override focusLost(FocusEvent fe) which will be called when JTextField loses focuses, i.e another component is selected.

However because you have a purpose:

I want to check my users forms for any illegal characters before they try to submit their data

Id suggest a read on How to Use the Focus Subsystem - Validating Input

Better options than a FocusAdapter - tailored made for validating/restricting user input:

• DocumentFilter. See here and this variation for an example.
• InputVerifier. See here for an example
• JFormattedTextField. See here for an example