MaskFormatter Patterns

MaskFormatter is used to format and edit strings. The behavior of a MaskFormatter is controlled by way of a String mask that specifies the valid characters that can be contained at a particular location in the Document model. The following characters can be specified:

Character  Description
# Any valid number, uses Character.isDigit.
' Escape character, used to escape any of the special formatting characters.
UAny character (Character.isLetter). All lowercase letters are mapped to upper case.
LAny character (Character.isLetter). All upper case letters are mapped to lower case.
AAny character or number (Character.isLetter or Character.isDigit)
?Any character (Character.isLetter).
*Anything.
HAny hex character (0-9, a-f or A-F).

(Excerpt from the Java API docs)