return new HeadersEntrySetIterator();
        }

        @Override
        public boolean remove(Object o) {
            throw new UnsupportedOperationException();
        }

        @Override
        public boolean removeAll(Collection<?> c) {
            throw new UnsupportedOperationException();
        }

        @Override
        public boolean retainAll(Collection<?> c) {
            throw new UnsupportedOperationException();
        }

        @Override
        public int size() {
            return HeaderValuesMap.this.size();
        }

        @Override
        public Object[] toArray() {
            return toList().toArray();
        }

        @Override
        public <T> T[] toArray(T[] a) {
            return toList().toArray(a);
        }

        /**
         * Checks whether the given entry is present in the headers.
         *
         * @param entry The entry to check.
         * @return <code></code> if the key and the values of the entry are present.
         */
        private boolean containsEntry(Map.Entry<String, String[]> entry) {

            return new ReadOnlyEnumerationMapEntrySetIterator();
        }

        @Override
        public boolean remove(Object o) {
            throw new UnsupportedOperationException();
        }

        @Override
        public boolean removeAll(Collection<?> c) {
            throw new UnsupportedOperationException();
        }

        @Override
        public boolean retainAll(Collection<?> c) {
            throw new UnsupportedOperationException();
        }

        @Override
        public int size() {
            return ReadOnlyEnumerationMap.this.size();
        }

        @Override
        public Object[] toArray() {
            return toList().toArray();
        }

        @Override
        public <T> T[] toArray(T[] a) {
            return toList().toArray(a);
        }