question: public Set < String > names ( ) { TreeSet < String > result = new TreeSet < > ( String . CASE_INSENSITIVE_ORDER ) ; for ( int i = 0 , size = size ( ) ; i < size ; i ++ ) { result . add ( name ( i ) ) ; } return Collections . unmodifiableSet ( result ) ; }
target:  Returns an immutable case-insensitive set of header names. 