code: private static String serialize(final Set set, final String sep) {
  	
  		Iterator it = set.iterator();
  	
  		String s = "";
  	
  		while (it.hasNext()) {
  			
  			s = s + it.next().toString();
  			
  			if (it.hasNext())
  				s = s + sep;
  		}
  		
  		return s;
  	}
docs: Serialises the items of a set into a string. Each item must have a
  meaningful {@code toString()} method.
  
  @param set The set to serialise.
  @param sep The string separator to apply.
  
  @return The serialised set as string.