code: public Object removeTail() {
  		if( last == null )
  			throw new IllegalArgumentException("Empty list");
  
  		Object ret = last.getObject();
  		Element<T> e = last;
  		available.add(last);
  
  		if( last.previous != null ) {
  			last.previous.next = null;
  			last = last.previous;
  		} else {
  			// there's only one element in the list
  			first = last = null;
  		}
  		e.clear();
  		size--;
  		return ret;
  	}
docs: Removes the last element from the list
  @return The object which was contained in the lsat element