code: public static String computeHeaderId(String headerNumber, String headerText) {
  		final String fullText = Strings.emptyIfNull(headerNumber) + " " + Strings.emptyIfNull(headerText); //$NON-NLS-1$
  		return computeHeaderId(fullText);
  	}
docs: Create the id of a section header.
  
  <p>The ID format follows the ReadCarpet standards.
  
  @param headerNumber the number of the header, or {@code null}.
  @param headerText the section header text.
  @return the identifier.