code: public String getComment(int index) {
  		if (comments == null || index < 0 || index >= comments.size()) {
  			throw new IllegalArgumentException("Not a valid comment index: " + index);
  		}
  		return (String)comments.get(index);
  	}
docs: Returns the index'th comment retrieved from the image.
  @throws IllegalArgumentException if index is smaller than 0 or larger than or equal
  to the number of comments retrieved
  @see #getNumberOfComments