code: private static String checkDisplayName(final FormItemList formItemList,
  			final CreateUserResponse createUserResponse) {
  		final String displayName = formItemList
  				.getField(ProtocolConstants.Parameters.Create.User.DISPLAY_NAME);
  		if (displayName != null) {
  			return displayName;
  		} else {
  			createUserResponse.displayNameMissing();
  		}
  
  		return null;
  	}
docs: check if the request contains a display name
  
  @param formItemList
  form item list extracted
  @param createUserResponse
  response object
  @return display name<br>
  <b>null</b> if there was no display name passed