code: public final void addDefaultMessage(final String key, final String value) {
          Validate.notNull(key, "Key for default message cannot be null");
          Validate.notNull(value, "Value for default message cannot be null");
          this.defaultMessages.put(key, value);
      }
docs: <p>
  Adds a new message to the set of default messages.
  </p>
  
  @param key the message key
  @param value the message value (text)