diff -r 000000000000 -r 212417b74b72 rt/emul/compact/src/main/java/java/util/concurrent/LinkedBlockingDeque.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/rt/emul/compact/src/main/java/java/util/concurrent/LinkedBlockingDeque.java	Sat Mar 19 10:46:31 2016 +0100
@@ -0,0 +1,1198 @@
+/*
+ * 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 Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent;
+
+import java.util.AbstractQueue;
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
+
+/**
+ * An optionally-bounded {@linkplain BlockingDeque blocking deque} based on
+ * linked nodes.
+ *
+ * <p> The optional capacity bound constructor argument serves as a
+ * way to prevent excessive expansion. The capacity, if unspecified,
+ * is equal to {@link Integer#MAX_VALUE}.  Linked nodes are
+ * dynamically created upon each insertion unless this would bring the
+ * deque above capacity.
+ *
+ * <p>Most operations run in constant time (ignoring time spent
+ * blocking).  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>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>.
+ *
+ * @since 1.6
+ * @author  Doug Lea
+ * @param <E> the type of elements held in this collection
+ */
+public class LinkedBlockingDeque<E>
+    extends AbstractQueue<E>
+    implements BlockingDeque<E>,  java.io.Serializable {
+
+    /*
+     * Implemented as a simple doubly-linked list protected by a
+     * single lock and using conditions to manage blocking.
+     *
+     * To implement weakly consistent iterators, it appears we need to
+     * keep all Nodes GC-reachable from a predecessor dequeued Node.
+     * That would cause two problems:
+     * - allow a rogue Iterator to cause unbounded memory retention
+     * - cause cross-generational linking of old Nodes to new Nodes if
+     *   a Node was tenured while live, which generational GCs have a
+     *   hard time dealing with, causing repeated major collections.
+     * However, only non-deleted Nodes need to be reachable from
+     * dequeued Nodes, and reachability does not necessarily have to
+     * be of the kind understood by the GC.  We use the trick of
+     * linking a Node that has just been dequeued to itself.  Such a
+     * self-link implicitly means to jump to "first" (for next links)
+     * or "last" (for prev links).
+     */
+
+    /*
+     * We have "diamond" multiple interface/abstract class inheritance
+     * here, and that introduces ambiguities. Often we want the
+     * BlockingDeque javadoc combined with the AbstractQueue
+     * implementation, so a lot of method specs are duplicated here.
+     */
+
+    private static final long serialVersionUID = -387911632671998426L;
+
+    /** Doubly-linked list node class */
+    static final class Node<E> {
+        /**
+         * The item, or null if this node has been removed.
+         */
+        E item;
+
+        /**
+         * One of:
+         * - the real predecessor Node
+         * - this Node, meaning the predecessor is tail
+         * - null, meaning there is no predecessor
+         */
+        Node<E> prev;
+
+        /**
+         * One of:
+         * - the real successor Node
+         * - this Node, meaning the successor is head
+         * - null, meaning there is no successor
+         */
+        Node<E> next;
+
+        Node(E x) {
+            item = x;
+        }
+    }
+
+    /**
+     * Pointer to first node.
+     * Invariant: (first == null && last == null) ||
+     *            (first.prev == null && first.item != null)
+     */
+    transient Node<E> first;
+
+    /**
+     * Pointer to last node.
+     * Invariant: (first == null && last == null) ||
+     *            (last.next == null && last.item != null)
+     */
+    transient Node<E> last;
+
+    /** Number of items in the deque */
+    private transient int count;
+
+    /** Maximum number of items in the deque */
+    private final int capacity;
+
+    /** Main lock guarding all access */
+    final ReentrantLock lock = new ReentrantLock();
+
+    /** Condition for waiting takes */
+    private final Condition notEmpty = lock.newCondition();
+
+    /** Condition for waiting puts */
+    private final Condition notFull = lock.newCondition();
+
+    /**
+     * Creates a {@code LinkedBlockingDeque} with a capacity of
+     * {@link Integer#MAX_VALUE}.
+     */
+    public LinkedBlockingDeque() {
+        this(Integer.MAX_VALUE);
+    }
+
+    /**
+     * Creates a {@code LinkedBlockingDeque} with the given (fixed) capacity.
+     *
+     * @param capacity the capacity of this deque
+     * @throws IllegalArgumentException if {@code capacity} is less than 1
+     */
+    public LinkedBlockingDeque(int capacity) {
+        if (capacity <= 0) throw new IllegalArgumentException();
+        this.capacity = capacity;
+    }
+
+    /**
+     * Creates a {@code LinkedBlockingDeque} with a capacity of
+     * {@link Integer#MAX_VALUE}, initially containing the elements of
+     * the given collection, added in traversal order of the
+     * collection's iterator.
+     *
+     * @param c the collection of elements to initially contain
+     * @throws NullPointerException if the specified collection or any
+     *         of its elements are null
+     */
+    public LinkedBlockingDeque(Collection<? extends E> c) {
+        this(Integer.MAX_VALUE);
+        final ReentrantLock lock = this.lock;
+        lock.lock(); // Never contended, but necessary for visibility
+        try {
+            for (E e : c) {
+                if (e == null)
+                    throw new NullPointerException();
+                if (!linkLast(new Node<E>(e)))
+                    throw new IllegalStateException("Deque full");
+            }
+        } finally {
+            lock.unlock();
+        }
+    }
+
+
+    // Basic linking and unlinking operations, called only while holding lock
+
+    /**
+     * Links node as first element, or returns false if full.
+     */
+    private boolean linkFirst(Node<E> node) {
+        // assert lock.isHeldByCurrentThread();
+        if (count >= capacity)
+            return false;
+        Node<E> f = first;
+        node.next = f;
+        first = node;
+        if (last == null)
+            last = node;
+        else
+            f.prev = node;
+        ++count;
+        notEmpty.signal();
+        return true;
+    }
+
+    /**
+     * Links node as last element, or returns false if full.
+     */
+    private boolean linkLast(Node<E> node) {
+        // assert lock.isHeldByCurrentThread();
+        if (count >= capacity)
+            return false;
+        Node<E> l = last;
+        node.prev = l;
+        last = node;
+        if (first == null)
+            first = node;
+        else
+            l.next = node;
+        ++count;
+        notEmpty.signal();
+        return true;
+    }
+
+    /**
+     * Removes and returns first element, or null if empty.
+     */
+    private E unlinkFirst() {
+        // assert lock.isHeldByCurrentThread();
+        Node<E> f = first;
+        if (f == null)
+            return null;
+        Node<E> n = f.next;
+        E item = f.item;
+        f.item = null;
+        f.next = f; // help GC
+        first = n;
+        if (n == null)
+            last = null;
+        else
+            n.prev = null;
+        --count;
+        notFull.signal();
+        return item;
+    }
+
+    /**
+     * Removes and returns last element, or null if empty.
+     */
+    private E unlinkLast() {
+        // assert lock.isHeldByCurrentThread();
+        Node<E> l = last;
+        if (l == null)
+            return null;
+        Node<E> p = l.prev;
+        E item = l.item;
+        l.item = null;
+        l.prev = l; // help GC
+        last = p;
+        if (p == null)
+            first = null;
+        else
+            p.next = null;
+        --count;
+        notFull.signal();
+        return item;
+    }
+
+    /**
+     * Unlinks x.
+     */
+    void unlink(Node<E> x) {
+        // assert lock.isHeldByCurrentThread();
+        Node<E> p = x.prev;
+        Node<E> n = x.next;
+        if (p == null) {
+            unlinkFirst();
+        } else if (n == null) {
+            unlinkLast();
+        } else {
+            p.next = n;
+            n.prev = p;
+            x.item = null;
+            // Don't mess with x's links.  They may still be in use by
+            // an iterator.
+            --count;
+            notFull.signal();
+        }
+    }
+
+    // BlockingDeque methods
+
+    /**
+     * @throws IllegalStateException {@inheritDoc}
+     * @throws NullPointerException  {@inheritDoc}
+     */
+    public void addFirst(E e) {
+        if (!offerFirst(e))
+            throw new IllegalStateException("Deque full");
+    }
+
+    /**
+     * @throws IllegalStateException {@inheritDoc}
+     * @throws NullPointerException  {@inheritDoc}
+     */
+    public void addLast(E e) {
+        if (!offerLast(e))
+            throw new IllegalStateException("Deque full");
+    }
+
+    /**
+     * @throws NullPointerException {@inheritDoc}
+     */
+    public boolean offerFirst(E e) {
+        if (e == null) throw new NullPointerException();
+        Node<E> node = new Node<E>(e);
+        final ReentrantLock lock = this.lock;
+        lock.lock();
+        try {
+            return linkFirst(node);
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    /**
+     * @throws NullPointerException {@inheritDoc}
+     */
+    public boolean offerLast(E e) {
+        if (e == null) throw new NullPointerException();
+        Node<E> node = new Node<E>(e);
+        final ReentrantLock lock = this.lock;
+        lock.lock();
+        try {
+            return linkLast(node);
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    /**
+     * @throws NullPointerException {@inheritDoc}
+     * @throws InterruptedException {@inheritDoc}
+     */
+    public void putFirst(E e) throws InterruptedException {
+        if (e == null) throw new NullPointerException();
+        Node<E> node = new Node<E>(e);
+        final ReentrantLock lock = this.lock;
+        lock.lock();
+        try {
+            while (!linkFirst(node))
+                notFull.await();
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    /**
+     * @throws NullPointerException {@inheritDoc}
+     * @throws InterruptedException {@inheritDoc}
+     */
+    public void putLast(E e) throws InterruptedException {
+        if (e == null) throw new NullPointerException();
+        Node<E> node = new Node<E>(e);
+        final ReentrantLock lock = this.lock;
+        lock.lock();
+        try {
+            while (!linkLast(node))
+                notFull.await();
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    /**
+     * @throws NullPointerException {@inheritDoc}
+     * @throws InterruptedException {@inheritDoc}
+     */
+    public boolean offerFirst(E e, long timeout, TimeUnit unit)
+        throws InterruptedException {
+        if (e == null) throw new NullPointerException();
+        Node<E> node = new Node<E>(e);
+        long nanos = unit.toNanos(timeout);
+        final ReentrantLock lock = this.lock;
+        lock.lockInterruptibly();
+        try {
+            while (!linkFirst(node)) {
+                if (nanos <= 0)
+                    return false;
+                nanos = notFull.awaitNanos(nanos);
+            }
+            return true;
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    /**
+     * @throws NullPointerException {@inheritDoc}
+     * @throws InterruptedException {@inheritDoc}
+     */
+    public boolean offerLast(E e, long timeout, TimeUnit unit)
+        throws InterruptedException {
+        if (e == null) throw new NullPointerException();
+        Node<E> node = new Node<E>(e);
+        long nanos = unit.toNanos(timeout);
+        final ReentrantLock lock = this.lock;
+        lock.lockInterruptibly();
+        try {
+            while (!linkLast(node)) {
+                if (nanos <= 0)
+                    return false;
+                nanos = notFull.awaitNanos(nanos);
+            }
+            return true;
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    /**
+     * @throws NoSuchElementException {@inheritDoc}
+     */
+    public E removeFirst() {
+        E x = pollFirst();
+        if (x == null) throw new NoSuchElementException();
+        return x;
+    }
+
+    /**
+     * @throws NoSuchElementException {@inheritDoc}
+     */
+    public E removeLast() {
+        E x = pollLast();
+        if (x == null) throw new NoSuchElementException();
+        return x;
+    }
+
+    public E pollFirst() {
+        final ReentrantLock lock = this.lock;
+        lock.lock();
+        try {
+            return unlinkFirst();
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    public E pollLast() {
+        final ReentrantLock lock = this.lock;
+        lock.lock();
+        try {
+            return unlinkLast();
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    public E takeFirst() throws InterruptedException {
+        final ReentrantLock lock = this.lock;
+        lock.lock();
+        try {
+            E x;
+            while ( (x = unlinkFirst()) == null)
+                notEmpty.await();
+            return x;
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    public E takeLast() throws InterruptedException {
+        final ReentrantLock lock = this.lock;
+        lock.lock();
+        try {
+            E x;
+            while ( (x = unlinkLast()) == null)
+                notEmpty.await();
+            return x;
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    public E pollFirst(long timeout, TimeUnit unit)
+        throws InterruptedException {
+        long nanos = unit.toNanos(timeout);
+        final ReentrantLock lock = this.lock;
+        lock.lockInterruptibly();
+        try {
+            E x;
+            while ( (x = unlinkFirst()) == null) {
+                if (nanos <= 0)
+                    return null;
+                nanos = notEmpty.awaitNanos(nanos);
+            }
+            return x;
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    public E pollLast(long timeout, TimeUnit unit)
+        throws InterruptedException {
+        long nanos = unit.toNanos(timeout);
+        final ReentrantLock lock = this.lock;
+        lock.lockInterruptibly();
+        try {
+            E x;
+            while ( (x = unlinkLast()) == null) {
+                if (nanos <= 0)
+                    return null;
+                nanos = notEmpty.awaitNanos(nanos);
+            }
+            return x;
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    /**
+     * @throws NoSuchElementException {@inheritDoc}
+     */
+    public E getFirst() {
+        E x = peekFirst();
+        if (x == null) throw new NoSuchElementException();
+        return x;
+    }
+
+    /**
+     * @throws NoSuchElementException {@inheritDoc}
+     */
+    public E getLast() {
+        E x = peekLast();
+        if (x == null) throw new NoSuchElementException();
+        return x;
+    }
+
+    public E peekFirst() {
+        final ReentrantLock lock = this.lock;
+        lock.lock();
+        try {
+            return (first == null) ? null : first.item;
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    public E peekLast() {
+        final ReentrantLock lock = this.lock;
+        lock.lock();
+        try {
+            return (last == null) ? null : last.item;
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    public boolean removeFirstOccurrence(Object o) {
+        if (o == null) return false;
+        final ReentrantLock lock = this.lock;
+        lock.lock();
+        try {
+            for (Node<E> p = first; p != null; p = p.next) {
+                if (o.equals(p.item)) {
+                    unlink(p);
+                    return true;
+                }
+            }
+            return false;
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    public boolean removeLastOccurrence(Object o) {
+        if (o == null) return false;
+        final ReentrantLock lock = this.lock;
+        lock.lock();
+        try {
+            for (Node<E> p = last; p != null; p = p.prev) {
+                if (o.equals(p.item)) {
+                    unlink(p);
+                    return true;
+                }
+            }
+            return false;
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    // BlockingQueue methods
+
+    /**
+     * Inserts the specified element at the end of this deque unless it would
+     * violate capacity restrictions.  When using a capacity-restricted deque,
+     * it is generally preferable to use method {@link #offer(Object) offer}.
+     *
+     * <p>This method is equivalent to {@link #addLast}.
+     *
+     * @throws IllegalStateException if the element cannot be added at this
+     *         time due to capacity restrictions
+     * @throws NullPointerException if the specified element is null
+     */
+    public boolean add(E e) {
+        addLast(e);
+        return true;
+    }
+
+    /**
+     * @throws NullPointerException if the specified element is null
+     */
+    public boolean offer(E e) {
+        return offerLast(e);
+    }
+
+    /**
+     * @throws NullPointerException {@inheritDoc}
+     * @throws InterruptedException {@inheritDoc}
+     */
+    public void put(E e) throws InterruptedException {
+        putLast(e);
+    }
+
+    /**
+     * @throws NullPointerException {@inheritDoc}
+     * @throws InterruptedException {@inheritDoc}
+     */
+    public boolean offer(E e, long timeout, TimeUnit unit)
+        throws InterruptedException {
+        return offerLast(e, timeout, unit);
+    }
+
+    /**
+     * Retrieves and removes the head of the queue represented by this deque.
+     * This method differs from {@link #poll poll} only in that it throws an
+     * exception if this deque is empty.
+     *
+     * <p>This method is equivalent to {@link #removeFirst() removeFirst}.
+     *
+     * @return the head of the queue represented by this deque
+     * @throws NoSuchElementException if this deque is empty
+     */
+    public E remove() {
+        return removeFirst();
+    }
+
+    public E poll() {
+        return pollFirst();
+    }
+
+    public E take() throws InterruptedException {
+        return takeFirst();
+    }
+
+    public E poll(long timeout, TimeUnit unit) throws InterruptedException {
+        return pollFirst(timeout, unit);
+    }
+
+    /**
+     * Retrieves, but does not remove, the head of the queue represented by
+     * this deque.  This method differs from {@link #peek peek} only in that
+     * it throws an exception if this deque is empty.
+     *
+     * <p>This method is equivalent to {@link #getFirst() getFirst}.
+     *
+     * @return the head of the queue represented by this deque
+     * @throws NoSuchElementException if this deque is empty
+     */
+    public E element() {
+        return getFirst();
+    }
+
+    public E peek() {
+        return peekFirst();
+    }
+
+    /**
+     * Returns the number of additional elements that this deque can ideally
+     * (in the absence of memory or resource constraints) accept without
+     * blocking. This is always equal to the initial capacity of this deque
+     * less the current {@code size} of this deque.
+     *
+     * <p>Note that you <em>cannot</em> always tell if an attempt to insert
+     * an element will succeed by inspecting {@code remainingCapacity}
+     * because it may be the case that another thread is about to
+     * insert or remove an element.
+     */
+    public int remainingCapacity() {
+        final ReentrantLock lock = this.lock;
+        lock.lock();
+        try {
+            return capacity - count;
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    /**
+     * @throws UnsupportedOperationException {@inheritDoc}
+     * @throws ClassCastException            {@inheritDoc}
+     * @throws NullPointerException          {@inheritDoc}
+     * @throws IllegalArgumentException      {@inheritDoc}
+     */
+    public int drainTo(Collection<? super E> c) {
+        return drainTo(c, Integer.MAX_VALUE);
+    }
+
+    /**
+     * @throws UnsupportedOperationException {@inheritDoc}
+     * @throws ClassCastException            {@inheritDoc}
+     * @throws NullPointerException          {@inheritDoc}
+     * @throws IllegalArgumentException      {@inheritDoc}
+     */
+    public int drainTo(Collection<? super E> c, int maxElements) {
+        if (c == null)
+            throw new NullPointerException();
+        if (c == this)
+            throw new IllegalArgumentException();
+        final ReentrantLock lock = this.lock;
+        lock.lock();
+        try {
+            int n = Math.min(maxElements, count);
+            for (int i = 0; i < n; i++) {
+                c.add(first.item);   // In this order, in case add() throws.
+                unlinkFirst();
+            }
+            return n;
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    // Stack methods
+
+    /**
+     * @throws IllegalStateException {@inheritDoc}
+     * @throws NullPointerException  {@inheritDoc}
+     */
+    public void push(E e) {
+        addFirst(e);
+    }
+
+    /**
+     * @throws NoSuchElementException {@inheritDoc}
+     */
+    public E pop() {
+        return removeFirst();
+    }
+
+    // Collection methods
+
+    /**
+     * Removes the first occurrence of the specified element from this deque.
+     * 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).
+     *
+     * <p>This method is equivalent to
+     * {@link #removeFirstOccurrence(Object) removeFirstOccurrence}.
+     *
+     * @param o element to be removed from this deque, if present
+     * @return {@code true} if this deque changed as a result of the call
+     */
+    public boolean remove(Object o) {
+        return removeFirstOccurrence(o);
+    }
+
+    /**
+     * Returns the number of elements in this deque.
+     *
+     * @return the number of elements in this deque
+     */
+    public int size() {
+        final ReentrantLock lock = this.lock;
+        lock.lock();
+        try {
+            return count;
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    /**
+     * Returns {@code true} if this deque contains the specified element.
+     * More formally, returns {@code true} if and only if this deque contains
+     * at least one element {@code e} such that {@code o.equals(e)}.
+     *
+     * @param o object to be checked for containment in this deque
+     * @return {@code true} if this deque contains the specified element
+     */
+    public boolean contains(Object o) {
+        if (o == null) return false;
+        final ReentrantLock lock = this.lock;
+        lock.lock();
+        try {
+            for (Node<E> p = first; p != null; p = p.next)
+                if (o.equals(p.item))
+                    return true;
+            return false;
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    /*
+     * TODO: Add support for more efficient bulk operations.
+     *
+     * We don't want to acquire the lock for every iteration, but we
+     * also want other threads a chance to interact with the
+     * collection, especially when count is close to capacity.
+     */
+
+//     /**
+//      * Adds all of the elements in the specified collection to this
+//      * queue.  Attempts to addAll of a queue to itself result in
+//      * {@code IllegalArgumentException}. Further, the behavior of
+//      * this operation is undefined if the specified collection is
+//      * modified while the operation is in progress.
+//      *
+//      * @param c collection containing elements to be added to this queue
+//      * @return {@code true} if this queue changed as a result of the call
+//      * @throws ClassCastException            {@inheritDoc}
+//      * @throws NullPointerException          {@inheritDoc}
+//      * @throws IllegalArgumentException      {@inheritDoc}
+//      * @throws IllegalStateException         {@inheritDoc}
+//      * @see #add(Object)
+//      */
+//     public boolean addAll(Collection<? extends E> c) {
+//         if (c == null)
+//             throw new NullPointerException();
+//         if (c == this)
+//             throw new IllegalArgumentException();
+//         final ReentrantLock lock = this.lock;
+//         lock.lock();
+//         try {
+//             boolean modified = false;
+//             for (E e : c)
+//                 if (linkLast(e))
+//                     modified = true;
+//             return modified;
+//         } finally {
+//             lock.unlock();
+//         }
+//     }
+
+    /**
+     * Returns an array containing all of the elements in this deque, in
+     * proper sequence (from first to last element).
+     *
+     * <p>The returned array will be "safe" in that no references to it are
+     * maintained by this deque.  (In other words, this method must allocate
+     * a new array).  The caller is thus free to modify the returned array.
+     *
+     * <p>This method acts as bridge between array-based and collection-based
+     * APIs.
+     *
+     * @return an array containing all of the elements in this deque
+     */
+    @SuppressWarnings("unchecked")
+    public Object[] toArray() {
+        final ReentrantLock lock = this.lock;
+        lock.lock();
+        try {
+            Object[] a = new Object[count];
+            int k = 0;
+            for (Node<E> p = first; p != null; p = p.next)
+                a[k++] = p.item;
+            return a;
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    /**
+     * Returns an array containing all of the elements in this deque, in
+     * proper sequence; the runtime type of the returned array is that of
+     * the specified array.  If the deque fits in the specified array, it
+     * is returned therein.  Otherwise, a new array is allocated with the
+     * runtime type of the specified array and the size of this deque.
+     *
+     * <p>If this deque fits in the specified array with room to spare
+     * (i.e., the array has more elements than this deque), the element in
+     * the array immediately following the end of the deque is set to
+     * {@code null}.
+     *
+     * <p>Like the {@link #toArray()} method, this method acts as bridge between
+     * array-based and collection-based APIs.  Further, this method allows
+     * precise control over the runtime type of the output array, and may,
+     * under certain circumstances, be used to save allocation costs.
+     *
+     * <p>Suppose {@code x} is a deque known to contain only strings.
+     * The following code can be used to dump the deque into a newly
+     * allocated array of {@code String}:
+     *
+     * <pre>
+     *     String[] y = x.toArray(new String[0]);</pre>
+     *
+     * Note that {@code toArray(new Object[0])} is identical in function to
+     * {@code toArray()}.
+     *
+     * @param a the array into which the elements of the deque are to
+     *          be stored, if it is big enough; otherwise, a new array of the
+     *          same runtime type is allocated for this purpose
+     * @return an array containing all of the elements in this deque
+     * @throws ArrayStoreException if the runtime type of the specified array
+     *         is not a supertype of the runtime type of every element in
+     *         this deque
+     * @throws NullPointerException if the specified array is null
+     */
+    @SuppressWarnings("unchecked")
+    public <T> T[] toArray(T[] a) {
+        final ReentrantLock lock = this.lock;
+        lock.lock();
+        try {
+            if (a.length < count)
+                a = (T[])java.lang.reflect.Array.newInstance
+                    (a.getClass().getComponentType(), count);
+
+            int k = 0;
+            for (Node<E> p = first; p != null; p = p.next)
+                a[k++] = (T)p.item;
+            if (a.length > k)
+                a[k] = null;
+            return a;
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    public String toString() {
+        final ReentrantLock lock = this.lock;
+        lock.lock();
+        try {
+            Node<E> p = first;
+            if (p == null)
+                return "[]";
+
+            StringBuilder sb = new StringBuilder();
+            sb.append('[');
+            for (;;) {
+                E e = p.item;
+                sb.append(e == this ? "(this Collection)" : e);
+                p = p.next;
+                if (p == null)
+                    return sb.append(']').toString();
+                sb.append(',').append(' ');
+            }
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    /**
+     * Atomically removes all of the elements from this deque.
+     * The deque will be empty after this call returns.
+     */
+    public void clear() {
+        final ReentrantLock lock = this.lock;
+        lock.lock();
+        try {
+            for (Node<E> f = first; f != null; ) {
+                f.item = null;
+                Node<E> n = f.next;
+                f.prev = null;
+                f.next = null;
+                f = n;
+            }
+            first = last = null;
+            count = 0;
+            notFull.signalAll();
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    /**
+     * Returns an iterator over the elements in this deque in proper sequence.
+     * The elements will be returned in order from first (head) to last (tail).
+     *
+     * <p>The returned iterator is a "weakly consistent" iterator that
+     * will never throw {@link java.util.ConcurrentModificationException
+     * ConcurrentModificationException}, and guarantees to traverse
+     * elements as they existed upon construction of the iterator, and
+     * may (but is not guaranteed to) reflect any modifications
+     * subsequent to construction.
+     *
+     * @return an iterator over the elements in this deque in proper sequence
+     */
+    public Iterator<E> iterator() {
+        return new Itr();
+    }
+
+    /**
+     * Returns an iterator over the elements in this deque in reverse
+     * sequential order.  The elements will be returned in order from
+     * last (tail) to first (head).
+     *
+     * <p>The returned iterator is a "weakly consistent" iterator that
+     * will never throw {@link java.util.ConcurrentModificationException
+     * ConcurrentModificationException}, and guarantees to traverse
+     * elements as they existed upon construction of the iterator, and
+     * may (but is not guaranteed to) reflect any modifications
+     * subsequent to construction.
+     *
+     * @return an iterator over the elements in this deque in reverse order
+     */
+    public Iterator<E> descendingIterator() {
+        return new DescendingItr();
+    }
+
+    /**
+     * Base class for Iterators for LinkedBlockingDeque
+     */
+    private abstract class AbstractItr implements Iterator<E> {
+        /**
+         * The next node to return in next()
+         */
+         Node<E> next;
+
+        /**
+         * nextItem holds on to item fields because once we claim that
+         * an element exists in hasNext(), we must return item read
+         * under lock (in advance()) even if it was in the process of
+         * being removed when hasNext() was called.
+         */
+        E nextItem;
+
+        /**
+         * Node returned by most recent call to next. Needed by remove.
+         * Reset to null if this element is deleted by a call to remove.
+         */
+        private Node<E> lastRet;
+
+        abstract Node<E> firstNode();
+        abstract Node<E> nextNode(Node<E> n);
+
+        AbstractItr() {
+            // set to initial position
+            final ReentrantLock lock = LinkedBlockingDeque.this.lock;
+            lock.lock();
+            try {
+                next = firstNode();
+                nextItem = (next == null) ? null : next.item;
+            } finally {
+                lock.unlock();
+            }
+        }
+
+        /**
+         * Returns the successor node of the given non-null, but
+         * possibly previously deleted, node.
+         */
+        private Node<E> succ(Node<E> n) {
+            // Chains of deleted nodes ending in null or self-links
+            // are possible if multiple interior nodes are removed.
+            for (;;) {
+                Node<E> s = nextNode(n);
+                if (s == null)
+                    return null;
+                else if (s.item != null)
+                    return s;
+                else if (s == n)
+                    return firstNode();
+                else
+                    n = s;
+            }
+        }
+
+        /**
+         * Advances next.
+         */
+        void advance() {
+            final ReentrantLock lock = LinkedBlockingDeque.this.lock;
+            lock.lock();
+            try {
+                // assert next != null;
+                next = succ(next);
+                nextItem = (next == null) ? null : next.item;
+            } finally {
+                lock.unlock();
+            }
+        }
+
+        public boolean hasNext() {
+            return next != null;
+        }
+
+        public E next() {
+            if (next == null)
+                throw new NoSuchElementException();
+            lastRet = next;
+            E x = nextItem;
+            advance();
+            return x;
+        }
+
+        public void remove() {
+            Node<E> n = lastRet;
+            if (n == null)
+                throw new IllegalStateException();
+            lastRet = null;
+            final ReentrantLock lock = LinkedBlockingDeque.this.lock;
+            lock.lock();
+            try {
+                if (n.item != null)
+                    unlink(n);
+            } finally {
+                lock.unlock();
+            }
+        }
+    }
+
+    /** Forward iterator */
+    private class Itr extends AbstractItr {
+        Node<E> firstNode() { return first; }
+        Node<E> nextNode(Node<E> n) { return n.next; }
+    }
+
+    /** Descending iterator */
+    private class DescendingItr extends AbstractItr {
+        Node<E> firstNode() { return last; }
+        Node<E> nextNode(Node<E> n) { return n.prev; }
+    }
+
+    /**
+     * Save the state of this deque to a stream (that is, serialize it).
+     *
+     * @serialData The capacity (int), followed by elements (each an
+     * {@code Object}) in the proper order, followed by a null
+     * @param s the stream
+     */
+    private void writeObject(java.io.ObjectOutputStream s)
+        throws java.io.IOException {
+        final ReentrantLock lock = this.lock;
+        lock.lock();
+        try {
+            // Write out capacity and any hidden stuff
+            s.defaultWriteObject();
+            // Write out all elements in the proper order.
+            for (Node<E> p = first; p != null; p = p.next)
+                s.writeObject(p.item);
+            // Use trailing null as sentinel
+            s.writeObject(null);
+        } finally {
+            lock.unlock();
+        }
+    }
+
+    /**
+     * Reconstitute this deque from a stream (that is,
+     * deserialize it).
+     * @param s the stream
+     */
+    private void readObject(java.io.ObjectInputStream s)
+        throws java.io.IOException, ClassNotFoundException {
+        s.defaultReadObject();
+        count = 0;
+        first = null;
+        last = null;
+        // Read in all elements and place in queue
+        for (;;) {
+            @SuppressWarnings("unchecked")
+            E item = (E)s.readObject();
+            if (item == null)
+                break;
+            add(item);
+        }
+    }
+
+}