How to limit a JTextArea to only accept a legal set of characters?

Question

Anybody know if there is an easy way to limit the allowed characters for a JTextArea. I.e. similar to JTextField using MaskFormatter.

Specifically I want to limit th

Answer 1

Try to extend PlainDocument and change the method insertString() to filter out all unwanted characters and replace lower with uppercase letters. Then you can use this special document in your JTextArea.