code: public static void notEmpty(String value, String message) throws IllegalArgumentException {
  		if (value == null || "".equals(value.trim())) {
  			throw new IllegalArgumentException("A precondition failed: " + message);
  		}
  	}
docs: Checks that a string is not null or empty.
  
  @param value the string to be tested.
  @param message the message for the exception in case the string is empty.
  
  @throws IllegalArgumentException if the string is empty.