code: public boolean contains(Object o) {
          if (o == null) return false;
          fullyLock();
          try {
              for (Node<E> p = head.next; p != null; p = p.next)
                  if (o.equals(p.item))
                      return true;
              return false;
          } finally {
              fullyUnlock();
          }
      }
docs: 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)}.
  
  @param o object to be checked for containment in this queue
  @return {@code true} if this queue contains the specified element