code: public static void notEmpty(final CharSequence str, final String parameterName) {
  		if (str == null || str.length() == 0) {
  			throw new IllegalArgumentException('"' + parameterName + "\" must not be null or empty, but was: " + str);
  		}
  	}
docs: Check that the provided string is not empty (not null, not "").
  
  @param str string to check
  @param parameterName name of the parameter to display in the error message