JTextField Constraints

set up a KeyListener to it which refuses to allow anything you don't want.

set up a KeyListener to it which refuses to allow anything you don't want.

May I get an example of how I would do that please. I don't know how to set up constraints at all. I don't really need it for what I'm doing but it would save me some trouble from throwing exceptions, unless the user copy and pastes the info into the textfield.

You can also use a JFormattedTextField: http://java.sun.com/docs/books/tutorial/uiswing/components/formattedtextfield.html
or an InputVerifier: http://java.sun.com/docs/books/tutorial/uiswing/misc/focus.html#inputVerification.

You can also use a JFormattedTextField: http://java.sun.com/docs/books/tutorial/uiswing/components/formattedtextfield.html
or an InputVerifier: http://java.sun.com/docs/books/tutorial/uiswing/misc/focus.html#inputVerification.

Thanks alot!

I tried some of the codes out and still couldn't find a solution. I'll give an example of what I'm trying to do. If I have a field named "JTextField num= new JTextField(10);", how can I make this particular field only accept number formats. It won't allow the user to input any letters at all before they even select enter.

Those things are covered by the tutorials that I linked above.

If you don't want to allow them to even type anything but numbers into field, you need to use the MaskFormatter: http://java.sun.com/docs/books/tutorial/uiswing/components/formattedtextfield.html#maskformatter
(Which you will see is covered in the first link I posted above on using JFormattedTextField)

If you don't want to allow them to even type anything but numbers into field, you need to use the MaskFormatter: http://java.sun.com/docs/books/tutorial/uiswing/components/formattedtextfield.html#maskformatter
(Which you will see is covered in the first link I posted above on using JFormattedTextField)

I looked through it, worked perfectly. Thanks alot for the help!