code: @Override
  	public int lastIndexOf(long elem) {
  		for (int i = size-1; i >= 0; i--)
  			if (elem==elementData[i])
  				return i;
  		return -1;
  	}
docs: Returns the index of the last occurrence of the specified object in
  this list.
  
  @param   elem   the desired element.
  @return  the index of the last occurrence of the specified object in
  this list; returns -1 if the object is not found.