question: public Map < String , List < String > > toMultimap ( boolean response ) { Map < String , List < String > > result = new TreeMap < String , List < String > > ( FIELD_NAME_COMPARATOR ) ; for ( int i = 0 ; i < namesAndValues . size ( ) ; i += 2 ) { String fieldName = namesAndValues . get ( i ) ; String value = namesAndValues . get ( i + 1 ) ; List < String > allValues = new ArrayList < String > ( ) ; List < String > otherValues = result . get ( fieldName ) ; if ( otherValues != null ) { allValues . addAll ( otherValues ) ; } allValues . add ( value ) ; result . put ( fieldName , Collections . unmodifiableList ( allValues ) ) ; } if ( response && statusLine != null ) { result . put ( null , Collections . unmodifiableList ( Collections . singletonList ( statusLine ) ) ) ; } else if ( requestLine != null ) { result . put ( null , Collections . unmodifiableList ( Collections . singletonList ( requestLine ) ) ) ; } return Collections . unmodifiableMap ( result ) ; }
target:  Returns an immutable map containing each field to its list of values. The status line is mapped to null.