code: private static String concat(final String... parts) {
  
  		final StringBuilder buf = new StringBuilder();
  
  		for (final String part : parts) {
  
  			// handle nulls gracefully (ignore)
  			if (part != null) {
  
  				buf.append(part);
  			}
  		}
  
  		return buf.toString();
  	}
docs: ----- private static methods -----