Regex constraint on a textfield

[Jess Dancel]

Hello, all.

I want to put a constraint on a JFormattedTextField that will only allow characters matching a regex to be entered (in this case, only hex digits 0-E).

The possible solutions I've found to this are all quite complicated. I know I've done it before and it was simple, but having trouble remembering.

[Jeanne Boyarsky]

Jess,
Welcome to JavaRanch!

This character class matches hex: [0-9A-E]

What else are you looking for that was complicated?

[Jessica Dancel]

I was wondering how to add that as a constraint to a textfield, so that the user can only enter those characters.

[Hiroshi Iwatani]

Use MaskFormatter. See the doc of the class for its usage.

[Jess Dancel]

Thank you, Hiroshi! MaskFormatter did exactly what I needed.