diff -r cdf768813b4d -r 79309d6eab38 jdk/src/share/classes/java/util/concurrent/LinkedBlockingDeque.java
--- a/jdk/src/share/classes/java/util/concurrent/LinkedBlockingDeque.java	Tue Jul 28 13:24:52 2009 -0700
+++ b/jdk/src/share/classes/java/util/concurrent/LinkedBlockingDeque.java	Tue Jul 28 17:17:55 2009 -0700
@@ -34,8 +34,13 @@
  */
 
 package java.util.concurrent;
-import java.util.*;
-import java.util.concurrent.locks.*;
+
+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
@@ -73,6 +78,20 @@
     /*
      * 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).
      */
 
     /*
@@ -86,9 +105,27 @@
 
     /** 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, Node<E> p, Node<E> n) {
             item = x;
             prev = p;
@@ -96,23 +133,37 @@
         }
     }
 
-    /** Pointer to first node */
-    private transient Node<E> first;
-    /** Pointer to last node */
-    private transient Node<E> last;
+    /**
+     * 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 */
-    private final ReentrantLock lock = new ReentrantLock();
+    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 <tt>LinkedBlockingDeque</tt> with a capacity of
+     * Creates a {@code LinkedBlockingDeque} with a capacity of
      * {@link Integer#MAX_VALUE}.
      */
     public LinkedBlockingDeque() {
@@ -120,10 +171,10 @@
     }
 
     /**
-     * Creates a <tt>LinkedBlockingDeque</tt> with the given (fixed) capacity.
+     * Creates a {@code LinkedBlockingDeque} with the given (fixed) capacity.
      *
      * @param capacity the capacity of this deque
-     * @throws IllegalArgumentException if <tt>capacity</tt> is less than 1
+     * @throws IllegalArgumentException if {@code capacity} is less than 1
      */
     public LinkedBlockingDeque(int capacity) {
         if (capacity <= 0) throw new IllegalArgumentException();
@@ -131,7 +182,7 @@
     }
 
     /**
-     * Creates a <tt>LinkedBlockingDeque</tt> with a capacity of
+     * 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.
@@ -142,8 +193,18 @@
      */
     public LinkedBlockingDeque(Collection<? extends E> c) {
         this(Integer.MAX_VALUE);
-        for (E e : c)
-            add(e);
+        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(e))
+                    throw new IllegalStateException("Deque full");
+            }
+        } finally {
+            lock.unlock();
+        }
     }
 
 
@@ -153,9 +214,9 @@
      * Links e as first element, or returns false if full.
      */
     private boolean linkFirst(E e) {
+        // assert lock.isHeldByCurrentThread();
         if (count >= capacity)
             return false;
-        ++count;
         Node<E> f = first;
         Node<E> x = new Node<E>(e, null, f);
         first = x;
@@ -163,6 +224,7 @@
             last = x;
         else
             f.prev = x;
+        ++count;
         notEmpty.signal();
         return true;
     }
@@ -171,9 +233,9 @@
      * Links e as last element, or returns false if full.
      */
     private boolean linkLast(E e) {
+        // assert lock.isHeldByCurrentThread();
         if (count >= capacity)
             return false;
-        ++count;
         Node<E> l = last;
         Node<E> x = new Node<E>(e, l, null);
         last = x;
@@ -181,6 +243,7 @@
             first = x;
         else
             l.next = x;
+        ++count;
         notEmpty.signal();
         return true;
     }
@@ -189,10 +252,14 @@
      * 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;
@@ -200,17 +267,21 @@
             n.prev = null;
         --count;
         notFull.signal();
-        return f.item;
+        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;
@@ -218,31 +289,29 @@
             p.next = null;
         --count;
         notFull.signal();
-        return l.item;
+        return item;
     }
 
     /**
-     * Unlink e
+     * Unlinks x.
      */
-    private void unlink(Node<E> x) {
+    void unlink(Node<E> x) {
+        // assert lock.isHeldByCurrentThread();
         Node<E> p = x.prev;
         Node<E> n = x.next;
         if (p == null) {
-            if (n == null)
-                first = last = null;
-            else {
-                n.prev = null;
-                first = n;
-            }
+            unlinkFirst();
         } else if (n == null) {
-            p.next = null;
-            last = p;
+            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();
         }
-        --count;
-        notFull.signalAll();
     }
 
     // BlockingDeque methods
@@ -270,6 +339,7 @@
      */
     public boolean offerFirst(E e) {
         if (e == null) throw new NullPointerException();
+        final ReentrantLock lock = this.lock;
         lock.lock();
         try {
             return linkFirst(e);
@@ -283,6 +353,7 @@
      */
     public boolean offerLast(E e) {
         if (e == null) throw new NullPointerException();
+        final ReentrantLock lock = this.lock;
         lock.lock();
         try {
             return linkLast(e);
@@ -297,6 +368,7 @@
      */
     public void putFirst(E e) throws InterruptedException {
         if (e == null) throw new NullPointerException();
+        final ReentrantLock lock = this.lock;
         lock.lock();
         try {
             while (!linkFirst(e))
@@ -312,6 +384,7 @@
      */
     public void putLast(E e) throws InterruptedException {
         if (e == null) throw new NullPointerException();
+        final ReentrantLock lock = this.lock;
         lock.lock();
         try {
             while (!linkLast(e))
@@ -329,15 +402,15 @@
         throws InterruptedException {
         if (e == null) throw new NullPointerException();
         long nanos = unit.toNanos(timeout);
+        final ReentrantLock lock = this.lock;
         lock.lockInterruptibly();
         try {
-            for (;;) {
-                if (linkFirst(e))
-                    return true;
+            while (!linkFirst(e)) {
                 if (nanos <= 0)
                     return false;
                 nanos = notFull.awaitNanos(nanos);
             }
+            return true;
         } finally {
             lock.unlock();
         }
@@ -351,15 +424,15 @@
         throws InterruptedException {
         if (e == null) throw new NullPointerException();
         long nanos = unit.toNanos(timeout);
+        final ReentrantLock lock = this.lock;
         lock.lockInterruptibly();
         try {
-            for (;;) {
-                if (linkLast(e))
-                    return true;
+            while (!linkLast(e)) {
                 if (nanos <= 0)
                     return false;
                 nanos = notFull.awaitNanos(nanos);
             }
+            return true;
         } finally {
             lock.unlock();
         }
@@ -384,6 +457,7 @@
     }
 
     public E pollFirst() {
+        final ReentrantLock lock = this.lock;
         lock.lock();
         try {
             return unlinkFirst();
@@ -393,6 +467,7 @@
     }
 
     public E pollLast() {
+        final ReentrantLock lock = this.lock;
         lock.lock();
         try {
             return unlinkLast();
@@ -402,6 +477,7 @@
     }
 
     public E takeFirst() throws InterruptedException {
+        final ReentrantLock lock = this.lock;
         lock.lock();
         try {
             E x;
@@ -414,6 +490,7 @@
     }
 
     public E takeLast() throws InterruptedException {
+        final ReentrantLock lock = this.lock;
         lock.lock();
         try {
             E x;
@@ -428,16 +505,16 @@
     public E pollFirst(long timeout, TimeUnit unit)
         throws InterruptedException {
         long nanos = unit.toNanos(timeout);
+        final ReentrantLock lock = this.lock;
         lock.lockInterruptibly();
         try {
-            for (;;) {
-                E x = unlinkFirst();
-                if (x != null)
-                    return x;
+            E x;
+            while ( (x = unlinkFirst()) == null) {
                 if (nanos <= 0)
                     return null;
                 nanos = notEmpty.awaitNanos(nanos);
             }
+            return x;
         } finally {
             lock.unlock();
         }
@@ -446,16 +523,16 @@
     public E pollLast(long timeout, TimeUnit unit)
         throws InterruptedException {
         long nanos = unit.toNanos(timeout);
+        final ReentrantLock lock = this.lock;
         lock.lockInterruptibly();
         try {
-            for (;;) {
-                E x = unlinkLast();
-                if (x != null)
-                    return x;
+            E x;
+            while ( (x = unlinkLast()) == null) {
                 if (nanos <= 0)
                     return null;
                 nanos = notEmpty.awaitNanos(nanos);
             }
+            return x;
         } finally {
             lock.unlock();
         }
@@ -480,6 +557,7 @@
     }
 
     public E peekFirst() {
+        final ReentrantLock lock = this.lock;
         lock.lock();
         try {
             return (first == null) ? null : first.item;
@@ -489,6 +567,7 @@
     }
 
     public E peekLast() {
+        final ReentrantLock lock = this.lock;
         lock.lock();
         try {
             return (last == null) ? null : last.item;
@@ -499,6 +578,7 @@
 
     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) {
@@ -515,6 +595,7 @@
 
     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) {
@@ -619,14 +700,15 @@
      * 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 <tt>size</tt> 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 <tt>remainingCapacity</tt>
+     * 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;
@@ -642,22 +724,7 @@
      * @throws IllegalArgumentException      {@inheritDoc}
      */
     public int drainTo(Collection<? super E> c) {
-        if (c == null)
-            throw new NullPointerException();
-        if (c == this)
-            throw new IllegalArgumentException();
-        lock.lock();
-        try {
-            for (Node<E> p = first; p != null; p = p.next)
-                c.add(p.item);
-            int n = count;
-            count = 0;
-            first = last = null;
-            notFull.signalAll();
-            return n;
-        } finally {
-            lock.unlock();
-        }
+        return drainTo(c, Integer.MAX_VALUE);
     }
 
     /**
@@ -671,19 +738,14 @@
             throw new NullPointerException();
         if (c == this)
             throw new IllegalArgumentException();
+        final ReentrantLock lock = this.lock;
         lock.lock();
         try {
-            int n = 0;
-            while (n < maxElements && first != null) {
-                c.add(first.item);
-                first.prev = null;
-                first = first.next;
-                --count;
-                ++n;
+            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();
             }
-            if (first == null)
-                last = null;
-            notFull.signalAll();
             return n;
         } finally {
             lock.unlock();
@@ -712,16 +774,16 @@
     /**
      * 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 <tt>e</tt> such that
-     * <tt>o.equals(e)</tt> (if such an element exists).
-     * Returns <tt>true</tt> if this deque contained the specified element
+     * 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 <tt>true</tt> if this deque changed as a result of the call
+     * @return {@code true} if this deque changed as a result of the call
      */
     public boolean remove(Object o) {
         return removeFirstOccurrence(o);
@@ -733,6 +795,7 @@
      * @return the number of elements in this deque
      */
     public int size() {
+        final ReentrantLock lock = this.lock;
         lock.lock();
         try {
             return count;
@@ -742,15 +805,16 @@
     }
 
     /**
-     * Returns <tt>true</tt> if this deque contains the specified element.
-     * More formally, returns <tt>true</tt> if and only if this deque contains
-     * at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>.
+     * 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 <tt>true</tt> if this deque contains the specified element
+     * @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)
@@ -762,24 +826,46 @@
         }
     }
 
-    /**
-     * Variant of removeFirstOccurrence needed by iterator.remove.
-     * Searches for the node, not its contents.
+    /*
+     * 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.
      */
-    boolean removeNode(Node<E> e) {
-        lock.lock();
-        try {
-            for (Node<E> p = first; p != null; p = p.next) {
-                if (p == e) {
-                    unlink(p);
-                    return true;
-                }
-            }
-            return false;
-        } finally {
-            lock.unlock();
-        }
-    }
+
+//     /**
+//      * 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
@@ -794,7 +880,9 @@
      *
      * @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];
@@ -817,22 +905,22 @@
      * <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
-     * <tt>null</tt>.
+     * {@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 <tt>x</tt> is a deque known to contain only strings.
+     * <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 <tt>String</tt>:
+     * allocated array of {@code String}:
      *
      * <pre>
      *     String[] y = x.toArray(new String[0]);</pre>
      *
-     * Note that <tt>toArray(new Object[0])</tt> is identical in function to
-     * <tt>toArray()</tt>.
+     * 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
@@ -843,14 +931,14 @@
      *         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
-                    );
+                a = (T[])java.lang.reflect.Array.newInstance
+                    (a.getClass().getComponentType(), count);
 
             int k = 0;
             for (Node<E> p = first; p != null; p = p.next)
@@ -864,6 +952,7 @@
     }
 
     public String toString() {
+        final ReentrantLock lock = this.lock;
         lock.lock();
         try {
             return super.toString();
@@ -877,8 +966,16 @@
      * 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();
@@ -890,7 +987,7 @@
     /**
      * 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).
-     * The returned <tt>Iterator</tt> is a "weakly consistent" iterator that
+     * The returned {@code Iterator} is a "weakly consistent" iterator that
      * will never throw {@link ConcurrentModificationException},
      * and guarantees to traverse elements as they existed upon
      * construction of the iterator, and may (but is not guaranteed to)
@@ -906,7 +1003,7 @@
      * 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).
-     * The returned <tt>Iterator</tt> is a "weakly consistent" iterator that
+     * The returned {@code Iterator} is a "weakly consistent" iterator that
      * will never throw {@link ConcurrentModificationException},
      * and guarantees to traverse elements as they existed upon
      * construction of the iterator, and may (but is not guaranteed to)
@@ -921,7 +1018,7 @@
      */
     private abstract class AbstractItr implements Iterator<E> {
         /**
-         * The next node to return in next
+         * The next node to return in next()
          */
          Node<E> next;
 
@@ -939,15 +1036,44 @@
          */
         private Node<E> lastRet;
 
+        abstract Node<E> firstNode();
+        abstract Node<E> nextNode(Node<E> n);
+
         AbstractItr() {
-            advance(); // set to initial position
+            // set to initial position
+            final ReentrantLock lock = LinkedBlockingDeque.this.lock;
+            lock.lock();
+            try {
+                next = firstNode();
+                nextItem = (next == null) ? null : next.item;
+            } finally {
+                lock.unlock();
+            }
         }
 
         /**
-         * Advances next, or if not yet initialized, sets to first node.
-         * Implemented to move forward vs backward in the two subclasses.
+         * Advances next.
          */
-        abstract void advance();
+        void advance() {
+            final ReentrantLock lock = LinkedBlockingDeque.this.lock;
+            lock.lock();
+            try {
+                // assert next != null;
+                Node<E> s = nextNode(next);
+                if (s == next) {
+                    next = firstNode();
+                } else {
+                    // Skip over removed nodes.
+                    // May be necessary if multiple interior Nodes are removed.
+                    while (s != null && s.item == null)
+                        s = nextNode(s);
+                    next = s;
+                }
+                nextItem = (next == null) ? null : next.item;
+            } finally {
+                lock.unlock();
+            }
+        }
 
         public boolean hasNext() {
             return next != null;
@@ -967,52 +1093,39 @@
             if (n == null)
                 throw new IllegalStateException();
             lastRet = null;
-            // Note: removeNode rescans looking for this node to make
-            // sure it was not already removed. Otherwise, trying to
-            // re-remove could corrupt list.
-            removeNode(n);
-        }
-    }
-
-    /** Forward iterator */
-    private class Itr extends AbstractItr {
-        void advance() {
             final ReentrantLock lock = LinkedBlockingDeque.this.lock;
             lock.lock();
             try {
-                next = (next == null)? first : next.next;
-                nextItem = (next == null)? null : next.item;
+                if (n.item != null)
+                    unlink(n);
             } finally {
                 lock.unlock();
             }
         }
     }
 
-    /**
-     * Descending iterator for LinkedBlockingDeque
-     */
+    /** 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 {
-        void advance() {
-            final ReentrantLock lock = LinkedBlockingDeque.this.lock;
-            lock.lock();
-            try {
-                next = (next == null)? last : next.prev;
-                nextItem = (next == null)? null : next.item;
-            } finally {
-                lock.unlock();
-            }
-        }
+        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
-     * <tt>Object</tt>) in the proper order, followed by a null
+     * {@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
@@ -1040,6 +1153,7 @@
         last = null;
         // Read in all elements and place in queue
         for (;;) {
+            @SuppressWarnings("unchecked")
             E item = (E)s.readObject();
             if (item == null)
                 break;