Spliterators.java 文件源码

/**
 * Creates an {@code PrimitiveIterator.OfDouble} from a
 * {@code Spliterator.OfDouble}.
 *
 * <p>Traversal of elements should be accomplished through the iterator.
 * The behaviour of traversal is undefined if the spliterator is operated
 * after the iterator is returned.
 *
 * @param spliterator The spliterator
 * @return An iterator
 * @throws NullPointerException if the given spliterator is {@code null}
 */
public static PrimitiveIterator.OfDouble iterator(Spliterator.OfDouble spliterator) {
    Objects.requireNonNull(spliterator);
    class Adapter implements PrimitiveIterator.OfDouble, DoubleConsumer {
        boolean valueReady = false;
        double nextElement;

        @Override
        public void accept(double t) {
            valueReady = true;
            nextElement = t;
        }

        @Override
        public boolean hasNext() {
            if (!valueReady)
                spliterator.tryAdvance(this);
            return valueReady;
        }

        @Override
        public double nextDouble() {
            if (!valueReady && !hasNext())
                throw new NoSuchElementException();
            else {
                valueReady = false;
                return nextElement;
            }
        }
    }

    return new Adapter();
}