question: @ SuppressWarnings ( { "regex" , "not.sef" } ) public static String regexError ( String s , int groups ) { try { Pattern p = Pattern . compile ( s ) ; int actualGroups = getGroupCount ( p ) ; if ( actualGroups < groups ) { return regexErrorMessage ( s , groups , actualGroups ) ; } } catch ( PatternSyntaxException e ) { return e . getMessage ( ) ; } return null ; }
target:  Returns null if the argument is a syntactically valid regular expression with at least the given number of groups. Otherwise returns a string describing why the argument is not a regex.