question: public XPatternTokenizer ( AttributeFactory factory , Pattern pattern , int group ) { super ( factory ) ; this . group = group ; matcher = pattern . matcher ( "" ) ; if ( group >= 0 && group > matcher . groupCount ( ) ) { throw new IllegalArgumentException ( "invalid group specified: pattern only has: " + matcher . groupCount ( ) + " capturing groups" ) ; } }
target:  creates a new PatternTokenizer returning tokens from group (-1 for split functionality) 