There are a lot of predefined character classes in Regex Pattern API. There are referred as shortcuts for regular expression:

. Any character
\d A digit- equivalent to [0-9]
\D A non-digit - equivalent to [^0-9]
\s A whitespace character - equivalent to [ \t\n\x0B\f\r]
\S A non-whitespace character- equivalent to [^\s]
\w A word character- equivalent to [a-zA-Z_0-9]
\W A non-word character- equivalent to [^\w]