Class ElementIterator

src/main/java/org/jsoup/parser/StreamParser.java:307–389

    }

    final class ElementIterator implements Iterator<Element>, NodeVisitor {
        // listeners add to a next emit queue, as a single token read step may yield multiple elements
        final private Queue<Element> emitQueue = new LinkedList<>();
        private @Nullable Element current;  // most recently emitted
        private @Nullable Element next;     // element waiting to be picked up
        private @Nullable Element tail;     // The last tailed element (</html>), on hold for final pop

        void reset() {
            emitQueue.clear();
            current = next = tail = null;
            stopped = false;
        }

        // Iterator Interface:
        /**
         {@inheritDoc}
         @throws UncheckedIOException if the underlying Reader errors during a read
         */
        @Override public boolean hasNext() {
            maybeFindNext();
            return next != null;
        }

        /**
         {@inheritDoc}
         @throws UncheckedIOException if the underlying Reader errors during a read
         */
        @Override public Element next() {
            maybeFindNext();
            if (next == null) throw new NoSuchElementException();
            current = next;
            next = null;
            return current;
        }

        private void maybeFindNext() {
            if (stopped || next != null) return;

            // drain the current queue before stepping to get more
            if (!emitQueue.isEmpty()) {
                next = emitQueue.remove();
                return;
            }

            // step the parser, which will hit the node listeners to add to the queue:
            while (treeBuilder.stepParser()) {
                if (!emitQueue.isEmpty()) {
                    next = emitQueue.remove();
                    return;
                }
            }
            stop();
            close();

            // send the final element out:
            if (tail != null) {
                next = tail;
                tail = null;