code: public <T> T[] toArray(T[] a) {
          final ReentrantLock lock = this.lock;
          lock.lock();
          try {
              return q.toArray(a);
          } finally {
              lock.unlock();
          }
      }
docs: 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
  {@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>The following code can be used to dump a delay queue into a newly
  allocated array of {@code Delayed}:
  
  <pre> {@code Delayed[] a = q.toArray(new Delayed[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 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