/*

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

/*

 * This file is available under and governed by the GNU General Public

 * License version 2 only, as published by the Free Software Foundation.

 * However, the following notice accompanied the original version of this

 * file:

 *

 * Written by Josh Bloch of Google Inc. and released to the public domain,

 * as explained at http://creativecommons.org/publicdomain/zero/1.0/.

 */

package java.util;

import java.io.Serializable;

import java.util.function.Consumer;

/**

 * Resizable-array implementation of the {@link Deque} interface.  Array

 * deques have no capacity restrictions; they grow as necessary to support

 * usage.  They are not thread-safe; in the absence of external

 * synchronization, they do not support concurrent access by multiple threads.

 * Null elements are prohibited.  This class is likely to be faster than

 * {@link Stack} when used as a stack, and faster than {@link LinkedList}

 * when used as a queue.

 *

 * <p>Most {@code ArrayDeque} operations run in amortized constant time.

 * Exceptions include

 * {@link #remove(Object) remove},

 * {@link #removeFirstOccurrence removeFirstOccurrence},

 * {@link #removeLastOccurrence removeLastOccurrence},

 * {@link #contains contains},

 * {@link #iterator iterator.remove()},

 * and the bulk operations, all of which run in linear time.

 *

 * <p>The iterators returned by this class's {@link #iterator() iterator}

 * method are <em>fail-fast</em>: If the deque is modified at any time after

 * the iterator is created, in any way except through the iterator's own

 * {@code remove} method, the iterator will generally throw a {@link

 * ConcurrentModificationException}.  Thus, in the face of concurrent

 * modification, the iterator fails quickly and cleanly, rather than risking

 * arbitrary, non-deterministic behavior at an undetermined time in the

 * future.

 *

 * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed

 * as it is, generally speaking, impossible to make any hard guarantees in the

 * presence of unsynchronized concurrent modification.  Fail-fast iterators

 * throw {@code ConcurrentModificationException} on a best-effort basis.

 * Therefore, it would be wrong to write a program that depended on this

 * exception for its correctness: <i>the fail-fast behavior of iterators

 * should be used only to detect bugs.</i>

 *

 * <p>This class and its iterator implement all of the

 * <em>optional</em> methods of the {@link Collection} and {@link

 * Iterator} interfaces.

 *

 * <p>This class is a member of the

 * <a href="{@docRoot}/../technotes/guides/collections/index.html">

 * Java Collections Framework</a>.

 *

 * @author  Josh Bloch and Doug Lea

 * @param <E> the type of elements held in this deque

 * @since   1.6

 */

public class ArrayDeque<E> extends AbstractCollection<E>

                           implements Deque<E>, Cloneable, Serializable

{

    /**

     * The array in which the elements of the deque are stored.

     */

    /**

     * The index of the element at the head of the deque (which is the

     * element that would be removed by remove() or pop()); or an

     */

    transient int head;

    /**

     * The index at which the next element would be added to the tail

     */

    transient int tail;

    /**

     */

    /**

     *

     */

        }

    }

    }

    /**

     * Constructs an empty array deque with an initial capacity

     * sufficient to hold 16 elements.

     */

    public ArrayDeque() {

        elements = new Object[16];

    }

    /**

     * Constructs an empty array deque with an initial capacity

     * sufficient to hold the specified number of elements.

     *

     */

    public ArrayDeque(int numElements) {

    }

    /**

     * Constructs a deque containing the elements of the specified

     * collection, in the order they are returned by the collection's

     * iterator.  (The first element returned by the collection's

     * iterator becomes the first element, or <i>front</i> of the

     * deque.)

     *

     * @param c the collection whose elements are to be placed into the deque

     * @throws NullPointerException if the specified collection is null

     */

    public ArrayDeque(Collection<? extends E> c) {

        addAll(c);

    }

    // The main insertion and extraction methods are addFirst,

    // addLast, pollFirst, pollLast. The other methods are defined in

    // terms of these.

    /**

     * Inserts the specified element at the front of this deque.

     *

     * @param e the element to add

     * @throws NullPointerException if the specified element is null

     */

    public void addFirst(E e) {

        if (e == null)

            throw new NullPointerException();

        if (head == tail)

    }

    /**

     * Inserts the specified element at the end of this deque.

     *

     * <p>This method is equivalent to {@link #add}.

     *

     * @param e the element to add

     * @throws NullPointerException if the specified element is null

     */

    public void addLast(E e) {

        if (e == null)

            throw new NullPointerException();

    }

    /**

     * Inserts the specified element at the front of this deque.

     *

     * @param e the element to add

     * @return {@code true} (as specified by {@link Deque#offerFirst})

     * @throws NullPointerException if the specified element is null

     */

    public boolean offerFirst(E e) {

        addFirst(e);

        return true;

    }

    /**

     * Inserts the specified element at the end of this deque.

     *

     * @param e the element to add

     * @return {@code true} (as specified by {@link Deque#offerLast})

     * @throws NullPointerException if the specified element is null

     */

    public boolean offerLast(E e) {

        addLast(e);

        return true;

    }

    /**

     * @throws NoSuchElementException {@inheritDoc}

     */

    public E removeFirst() {

            throw new NoSuchElementException();

    }

    /**

     * @throws NoSuchElementException {@inheritDoc}

     */

    public E removeLast() {

            throw new NoSuchElementException();

    }

    public E pollFirst() {

        }

    }

    public E pollLast() {

    }

    /**

     * @throws NoSuchElementException {@inheritDoc}

     */

    public E getFirst() {

            throw new NoSuchElementException();

    }

    /**

     * @throws NoSuchElementException {@inheritDoc}

     */

    public E getLast() {

            throw new NoSuchElementException();

    }

    public E peekFirst() {

    }

    public E peekLast() {

    }

    /**

     * Removes the first occurrence of the specified element in this

     * deque (when traversing the deque from head to tail).

     * If the deque does not contain the element, it is unchanged.

     * More formally, removes the first element {@code e} such that

     * {@code o.equals(e)} (if such an element exists).

     * Returns {@code true} if this deque contained the specified element

     * (or equivalently, if this deque changed as a result of the call).

     *

     * @param o element to be removed from this deque, if present

     * @return {@code true} if the deque contained the specified element

     */

    public boolean removeFirstOccurrence(Object o) {

        if (o != null) {

            }

        }

        return false;

    }

    /**

     * Removes the last occurrence of the specified element in this

     * deque (when traversing the deque from head to tail).

     * If the deque does not contain the element, it is unchanged.

     * More formally, removes the last element {@code e} such that

     * {@code o.equals(e)} (if such an element exists).

     * Returns {@code true} if this deque contained the specified element

     * (or equivalently, if this deque changed as a result of the call).

     *

     * @param o element to be removed from this deque, if present

     * @return {@code true} if the deque contained the specified element

     */

    public boolean removeLastOccurrence(Object o) {

        if (o != null) {

            }

        }

        return false;

    }

    // *** Queue methods ***

    /**

     * Inserts the specified element at the end of this deque.

     *

     * <p>This method is equivalent to {@link #addLast}.

     *

     * @param e the element to add

     * @return {@code true} (as specified by {@link Collection#add})

     * @throws NullPointerException if the specified element is null

     */

    public boolean add(E e) {

        addLast(e);

        return true;

    }

    /**

     * Inserts the specified element at the end of this deque.

     *

     * <p>This method is equivalent to {@link #offerLast}.

     *

     * @param e the element to add

     * @return {@code true} (as specified by {@link Queue#offer})

     * @throws NullPointerException if the specified element is null

     */

    public boolean offer(E e) {

        return offerLast(e);