public DelayQueue() 
{

}

Creates a new DelayQueue that is initially empty.

 public DelayQueue(Collection<? extends E> c) 
{
        this.addAll(c);
}

Creates a DelayQueue initially containing the elements of the given collection of Delayed instances.

Parameters:

c - the collection of elements to initially contain

Throws:

NullPointerException - if the specified collection or any of its elements are null

 public boolean add(E e) 
{
        return offer(e);
}

Inserts the specified element into this delay queue.

 public  void clear() 
{
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            q.clear();
        } finally {
            lock.unlock();
        }
}

Atomically removes all of the elements from this delay queue. The queue will be empty after this call returns. Elements with an unexpired delay are not waited for; they are simply discarded from the queue.

 public int drainTo(Collection<? super E> c) 
{
        if (c == null)
            throw new NullPointerException();
        if (c == this)
            throw new IllegalArgumentException();
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            int n = 0;
            for (;;) {
                E first = q.peek();
                if (first == null || first.getDelay(TimeUnit.NANOSECONDS)  > 0)
                    break;
                c.add(q.poll());
                ++n;
            }
            return n;
        } finally {
            lock.unlock();
        }
}

 public int drainTo(Collection<? super E> c,
    int maxElements) 
{
        if (c == null)
            throw new NullPointerException();
        if (c == this)
            throw new IllegalArgumentException();
        if (maxElements < = 0)
            return 0;
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            int n = 0;
            while (n <  maxElements) {
                E first = q.peek();
                if (first == null || first.getDelay(TimeUnit.NANOSECONDS)  > 0)
                    break;
                c.add(q.poll());
                ++n;
            }
            return n;
        } finally {
            lock.unlock();
        }
}

 public Iterator<E> iterator() 
{
        return new Itr(toArray());
}

Returns an iterator over all the elements (both expired and unexpired) in this queue. The iterator does not return the elements in any particular order.

The returned iterator is a "weakly consistent" iterator that will never throw 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.

 public boolean offer(E e) 
{
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            q.offer(e);
            if (q.peek() == e) {
                leader = null;
                available.signal();
            }
            return true;
        } finally {
            lock.unlock();
        }
}

Inserts the specified element into this delay queue.

 public boolean offer(E e,
    long timeout,
    TimeUnit unit) 
{
        return offer(e);
}

Inserts the specified element into this delay queue. As the queue is unbounded this method will never block.

 public E peek() 
{
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            return q.peek();
        } finally {
            lock.unlock();
        }
}

Retrieves, but does not remove, the head of this queue, or returns null if this queue is empty. Unlike poll, if no expired elements are available in the queue, this method returns the element that will expire next, if one exists.

 public E poll() 
{
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            E first = q.peek();
            if (first == null || first.getDelay(TimeUnit.NANOSECONDS)  > 0)
                return null;
            else
                return q.poll();
        } finally {
            lock.unlock();
        }
}

Retrieves and removes the head of this queue, or returns null if this queue has no elements with an expired delay.

 public E poll(long timeout,
    TimeUnit unit) throws InterruptedException 
{
        long nanos = unit.toNanos(timeout);
        final ReentrantLock lock = this.lock;
        lock.lockInterruptibly();
        try {
            for (;;) {
                E first = q.peek();
                if (first == null) {
                    if (nanos < = 0)
                        return null;
                    else
                        nanos = available.awaitNanos(nanos);
                } else {
                    long delay = first.getDelay(TimeUnit.NANOSECONDS);
                    if (delay < = 0)
                        return q.poll();
                    if (nanos < = 0)
                        return null;
                    if (nanos <  delay || leader != null)
                        nanos = available.awaitNanos(nanos);
                    else {
                        Thread thisThread = Thread.currentThread();
                        leader = thisThread;
                        try {
                            long timeLeft = available.awaitNanos(delay);
                            nanos -= delay - timeLeft;
                        } finally {
                            if (leader == thisThread)
                                leader = null;
                        }
                    }
                }
            }
        } finally {
            if (leader == null && q.peek() != null)
                available.signal();
            lock.unlock();
        }
}

Retrieves and removes the head of this queue, waiting if necessary until an element with an expired delay is available on this queue, or the specified wait time expires.

 public  void put(E e) 
{
        offer(e);
}

Inserts the specified element into this delay queue. As the queue is unbounded this method will never block.

 public int remainingCapacity() 
{
        return Integer.MAX_VALUE;
}

Always returns Integer.MAX_VALUE because a DelayQueue is not capacity constrained.

 public boolean remove(Object o) 
{
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            return q.remove(o);
        } finally {
            lock.unlock();
        }
}

Removes a single instance of the specified element from this queue, if it is present, whether or not it has expired.

 public int size() 
{
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            return q.size();
        } finally {
            lock.unlock();
        }
}

 public E take() throws InterruptedException 
{
        final ReentrantLock lock = this.lock;
        lock.lockInterruptibly();
        try {
            for (;;) {
                E first = q.peek();
                if (first == null)
                    available.await();
                else {
                    long delay = first.getDelay(TimeUnit.NANOSECONDS);
                    if (delay < = 0)
                        return q.poll();
                    else if (leader != null)
                        available.await();
                    else {
                        Thread thisThread = Thread.currentThread();
                        leader = thisThread;
                        try {
                            available.awaitNanos(delay);
                        } finally {
                            if (leader == thisThread)
                                leader = null;
                        }
                    }
                }
            }
        } finally {
            if (leader == null && q.peek() != null)
                available.signal();
            lock.unlock();
        }
}

Retrieves and removes the head of this queue, waiting if necessary until an element with an expired delay is available on this queue.

 public Object[] toArray() 
{
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            return q.toArray();
        } finally {
            lock.unlock();
        }
}

Returns an array containing all of the elements in this queue. The returned array elements are in no particular order.

The returned array will be "safe" in that no references to it are maintained by this queue. (In other words, this method must allocate a new array). The caller is thus free to modify the returned array.

This method acts as bridge between array-based and collection-based APIs.

 public T[] toArray(T[] a) 
{
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            return q.toArray(a);
        } finally {
            lock.unlock();
        }
}

Returns an array containing all of the elements in this queue; the runtime type of the returned array is that of the specified array. The returned array elements are in no particular order. If the queue 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 queue.

If this queue fits in the specified array with room to spare (i.e., the array has more elements than this queue), the element in the array immediately following the end of the queue is set to null.

Like the #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.

The following code can be used to dump a delay queue into a newly allocated array of Delayed:

    Delayed[] a = q.toArray(new Delayed[0]);

Note that toArray(new Object[0]) is identical in function to toArray().