public PriorityBlockingQueue() 
{
                             
        q = new PriorityQueue< E >();
}

Creates a PriorityBlockingQueue with the default initial capacity (11) that orders its elements according to their {@linkplain Comparable natural ordering}.

 public PriorityBlockingQueue(int initialCapacity) 
{
        q = new PriorityQueue< E >(initialCapacity, null);
}

Creates a PriorityBlockingQueue with the specified initial capacity that orders its elements according to their {@linkplain Comparable natural ordering}.

Parameters:

initialCapacity - the initial capacity for this priority queue

Throws:

IllegalArgumentException - if initialCapacity is less than 1

 public PriorityBlockingQueue(Collection c) 
{
        q = new PriorityQueue< E >(c);
}

Creates a PriorityBlockingQueue containing the elements in the specified collection. If the specified collection is a SortedSet or a PriorityQueue , this priority queue will be ordered according to the same ordering. Otherwise, this priority queue will be ordered according to the {@linkplain Comparable natural ordering} of its elements.

Parameters:

c - the collection whose elements are to be placed into this priority queue

Throws:

ClassCastException - if elements of the specified collection cannot be compared to one another according to the priority queue's ordering

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

 public PriorityBlockingQueue(int initialCapacity,
    Comparator comparator) 
{
        q = new PriorityQueue< E >(initialCapacity, comparator);
}

Creates a PriorityBlockingQueue with the specified initial capacity that orders its elements according to the specified comparator.

Parameters:

initialCapacity - the initial capacity for this priority queue

comparator - the comparator that will be used to order this priority queue. If {@code null}, the {@linkplain Comparable natural ordering} of the elements will be used.

Throws:

IllegalArgumentException - if initialCapacity is less than 1

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

Inserts the specified element into this priority 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 queue. The queue will be empty after this call returns.

 public Comparator comparator() 
{
        return q.comparator();
}

Returns the comparator used to order the elements in this queue, or null if this queue uses the {@linkplain Comparable natural ordering} of its elements.

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

Returns {@code true} if this queue contains the specified element. More formally, returns {@code true} if and only if this queue contains at least one element {@code e} such that {@code o.equals(e)}.

 public int drainTo(Collection c) 
{
        if (c == null)
            throw new NullPointerException();
        if (c == this)
            throw new IllegalArgumentException();
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            int n = 0;
            E e;
            while ( (e = q.poll()) != null) {
                c.add(e);
                ++n;
            }
            return n;
        } finally {
            lock.unlock();
        }
}

 public int drainTo(Collection 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;
            E e;
            while (n <  maxElements && (e = q.poll()) != null) {
                c.add(e);
                ++n;
            }
            return n;
        } finally {
            lock.unlock();
        }
}

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

Returns an iterator over the elements 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 {
            boolean ok = q.offer(e);
            assert ok;
            notEmpty.signal();
            return true;
        } finally {
            lock.unlock();
        }
}

Inserts the specified element into this priority queue.

 public boolean offer(E e,
    long timeout,
    TimeUnit unit) 
{
        return offer(e); // never need to block
}

Inserts the specified element into this priority 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();
        }
}

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

 public E poll(long timeout,
    TimeUnit unit) throws InterruptedException 
{
        long nanos = unit.toNanos(timeout);
        final ReentrantLock lock = this.lock;
        lock.lockInterruptibly();
        try {
            for (;;) {
                E x = q.poll();
                if (x != null)
                    return x;
                if (nanos < = 0)
                    return null;
                try {
                    nanos = notEmpty.awaitNanos(nanos);
                } catch (InterruptedException ie) {
                    notEmpty.signal(); // propagate to non-interrupted thread
                    throw ie;
                }
            }
        } finally {
            lock.unlock();
        }
}

 public  void put(E e) 
{
        offer(e); // never need to block
}

Inserts the specified element into this priority 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 PriorityBlockingQueue 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. More formally, removes an element {@code e} such that {@code o.equals(e)}, if this queue contains one or more such elements. Returns {@code true} if and only if this queue contained the specified element (or equivalently, if this queue changed as a result of the call).

 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 {
            try {
                while (q.size() == 0)
                    notEmpty.await();
            } catch (InterruptedException ie) {
                notEmpty.signal(); // propagate to non-interrupted thread
                throw ie;
            }
            E x = q.poll();
            assert x != null;
            return x;
        } finally {
            lock.unlock();
        }
}

 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.

Suppose x is a queue known to contain only strings. The following code can be used to dump the queue into a newly allocated array of String:

String[] y = x.toArray(new String[0]);

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

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