Error on tutorial page http://download.oracle.com/javase/tutorial/essential/regex/literals.html
quote: The metacharacters supported by this API are: ([{\^-$|]})?*+.

The characters <, !, and = are ommitted in this list. Java regex, for all practical matters being perl 5 regex, support positive and negative lookahead and lookbehind:

foo(?=bar)
foo(?!bar)
(?<=foo)bar
(?<!foo)bar