public List<String> groupNames() {
        if (groupNames == null) {
            groupNames = new ArrayList<String>(groupInfo.keySet());
        }
        return groupNames;
    }
public List<String> groupNames() {
        if (groupNames == null) {
            groupNames = new ArrayList<String>(groupInfo.keySet());
        }
        return groupNames;
    }
public List < String > groupNames ( ) { if ( groupNames == null ) { groupNames = new ArrayList < String > ( groupInfo . keySet ( ) ) ; } return groupNames ; }
Gets the names of all capture groups

@return the list of names
Gets the names of all capture groups