code: public final T add(T element) {
      size++;
      heap[size] = element;
      upHeap();
      return heap[1];
    }
docs: Adds an Object to a PriorityQueue in log(size) time. If one tries to add
  more objects than maxSize from initialize an
  {@link ArrayIndexOutOfBoundsException} is thrown.
  
  @return the new 'top' element in the queue.