@Override
  public boolean add(E e) {
    addLast(e);
    return true;
  }
Inserts the specified element to the deque unless it would
violate capacity restrictions.  When using a capacity-restricted deque,
it is generally preferable to use method {@link #offer(Object) offer}.
<br>
This method is equivalent to {@link #addLast}.

@throws IllegalStateException if the element cannot be added at this
                              time due to capacity restrictions
@throws NullPointerException  if the specified element is null
llap-server/src/java/org/apache/hadoop/hive/llap/daemon/impl/PriorityBlockingDeque.java