code: public void setComment(String key, String comment) {
  	if (comment == null)
  	    throw new NullPointerException();
          setRawComment(key, uncookComment(comment));
      }
docs: Sets the comment for the specified key.  Each line of the comment
  will be preceded by the comment marker "#", and leading and
  trailing whitespace will not be preserved.
  <br>
  Note: if you set a comment, you must set a corresponding value before
  calling store or storeToXML.
  
  @param key property key whose comment should be set
  @param comment comment to go with property key, "" for no comment