code: private static void validateKey(String key) {
  		if (key == null || key.length() > MAX_KEY_SIZE) {
  			throw new IllegalArgumentException("Invalid key - must be non null and have a length less than " + MAX_KEY_SIZE);
  		}
  	}
docs: Validates the given key.
  
  @param key the key to validate.
  @throws IllegalArgumentException if the {@code key} is {@code null} or its length is higher than the maximum allowed
  ({@value #MAX_KEY_SIZE}).