Class ArrayDeque

vm/JavaAPI/src/java/util/ArrayDeque.java:33–750

An implementation of Deque, backed by an array. ArrayDeques have no size limit, can not contain null element, and they are not thread-safe. All optional operations are supported, and the elements can be any objects. @param the type of elements in this collection @since 1.6

 * @since 1.6
 */
public class ArrayDeque<E> extends AbstractCollection<E> implements Deque<E> {

    private static final int DEFAULT_SIZE = 16;

    private enum DequeStatus {
        Empty, Normal, Full;
    }

    private transient DequeStatus status;

    private transient int modCount;

    // the pointer of the head element
    private transient int front;

    // the pointer of the "next" position of the tail element
    private transient int rear;

    private transient E[] elements;

    @SuppressWarnings("hiding")
    private class ArrayDequeIterator<E> implements Iterator<E> {
        private int pos;

        private final int expectedModCount;

        private boolean canRemove;

        @SuppressWarnings("synthetic-access")
        ArrayDequeIterator() {
            super();
            pos = front;
            expectedModCount = modCount;
            canRemove = false;
        }

        @SuppressWarnings("synthetic-access")
        public boolean hasNext() {
            if (expectedModCount != modCount) {
                return false;
            }
            return hasNextInternal();
        }

        private boolean hasNextInternal() {
            // canRemove means "next" method is called, and the Full
            // status can ensure that this method is not called just
            // after "remove" method is call.(so, canRemove can keep
            // true after "next" method called)
            return (pos != rear)
                    || ((status == DequeStatus.Full) && !canRemove);
        }

        @SuppressWarnings( { "synthetic-access", "unchecked" })
        public E next() {
            if (hasNextInternal()) {
                E result = (E) elements[pos];
                if (expectedModCount == modCount && null != result) {