/**
* Retrieves and removes the head of this queue, waiting if necessary until an element with an
* expired delay is available on this queue.
*
* @return the head of this queue
* @throws InterruptedException {@inheritDoc}
*/
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, or the specified wait time expires.
*
* @return the head of this queue, or <tt>null</tt> if the specified waiting time elapses before
* an element with an expired delay becomes available
* @throws InterruptedException {@inheritDoc}
*/
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.
*
* @return the head of this queue, or <tt>null</tt> if the specified waiting time elapses before
* an element with an expired delay becomes available
* @throws InterruptedException {@inheritDoc}
*/
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) {
if (nanos <= 0) return null;
if (delay > nanos) delay = nanos;
long timeLeft = available.awaitNanos(delay);
nanos -= delay - timeLeft;
} else {
E x = q.poll();
assert x != null;
if (q.size() != 0) available.signalAll();
return x;
}
}
}
} finally {
lock.unlock();
}
}
/**
* Retrieves and removes the head of this queue, or returns <tt>null</tt> if this queue has no
* elements with an expired delay.
*
* @return the head of this queue, or <tt>null</tt> if this queue has no elements with an expired
* delay
*/
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();
}
}
/**
* Inserts the specified element into this delay queue.
*
* @param e the element to add
* @return <tt>true</tt>
* @throws NullPointerException if the specified element is null
*/
public boolean offer(E e) {
final ReentrantLock lock = this.lock;
lock.lock();
try {
E first = q.peek();
q.offer(e);
if (first == null || e.compareTo(first) < 0) available.signalAll();
return true;
} finally {
lock.unlock();
}
}
/**
* Inserts the specified element into this delay queue.
*
* @param e the element to add
* @return <tt>true</tt>
* @throws NullPointerException if the specified element is null
*/
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();
}
}
/**
* Retrieves and removes the head of this queue, or returns <tt>null</tt> if this queue has no
* elements with an expired delay.
*
* @return the head of this queue, or <tt>null</tt> if this queue has no elements with an expired
* delay
*/
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 {
E x = q.poll();
assert x != null;
if (q.size() != 0) available.signalAll();
return x;
}
} 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 boolean remove(Object o) {
final ReentrantLock lock = this.lock;
lock.lock();
try {
return q.remove(o);
} 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.
*
* <p>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 <tt>null</tt>.
*
* <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>The following code can be used to dump a delay queue into a newly allocated array of
* <tt>Delayed</tt>:
*
* <pre>
* Delayed[] a = q.toArray(new Delayed[0]);</pre>
*
* Note that <tt>toArray(new Object[0])</tt> is identical in function to <tt>toArray()</tt>.
*
* @param a the array into which the elements of the queue 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 queue
* @throws ArrayStoreException if the runtime type of the specified array is not a supertype of
* the runtime type of every element in this queue
* @throws NullPointerException if the specified array is null
*/
public <T> 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 returned array elements are
* in no particular order.
*
* <p>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.
*
* <p>This method acts as bridge between array-based and collection-based APIs.
*
* @return an array containing all of the elements in this queue
*/
public Object[] toArray() {
final ReentrantLock lock = this.lock;
lock.lock();
try {
return q.toArray();
} 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 void clear() {
final ReentrantLock lock = this.lock;
lock.lock();
try {
q.clear();
} finally {
lock.unlock();
}
}
/**
* @throws UnsupportedOperationException {@inheritDoc}
* @throws ClassCastException {@inheritDoc}
* @throws NullPointerException {@inheritDoc}
* @throws IllegalArgumentException {@inheritDoc}
*/
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 size() {
final ReentrantLock lock = this.lock;
lock.lock();
try {
return q.size();
} finally {
lock.unlock();
}
}
/**
* Retrieves, but does not remove, the head of this queue, or returns <tt>null</tt> if this queue
* is empty. Unlike <tt>poll</tt>, if no expired elements are available in the queue, this method
* returns the element that will expire next, if one exists.
*
* @return the head of this queue, or <tt>null</tt> if this queue is empty.
*/
public E peek() {
final ReentrantLock lock = this.lock;
lock.lock();
try {
return q.peek();
} finally {
lock.unlock();
}
}
/**
* @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();
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;
}
if (n > 0) available.signalAll();
return n;
} finally {
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.
*
* @return the head of this queue
* @throws InterruptedException {@inheritDoc}
*/
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) {
long tl = available.awaitNanos(delay);
} else {
E x = q.poll();
assert x != null;
if (q.size() != 0) available.signalAll(); // wake up other takers
return x;
}
}
}
} finally {
lock.unlock();
}
}
