Constraining Input in JTextField

[kataya]

I am writing a program that has a bunch of little JTextFields fields (sudoku). Ideally each of these text fields will only accept one character. Using setColumns() or defining the number of columns in the constructor only limits the size of the display, not the amount of text accepted. Any ideas? Perhaps JTextField is not the correct component to use in this situation? Thanks in advance.

[hardwired]

See Implementing a Document Filter on Text Component Features which has an example.