code: protected String resolveCodeWithoutArguments(String code, Locale locale) {
          MessageFormat messageFormat = resolveCode(code, locale);
          if (messageFormat != null) {
              synchronized (messageFormat) {
                  return messageFormat.format(new Object[0]);
              }
          } else {
              return null;
          }
      }
docs: Subclasses can override this method to resolve a message without arguments
  in an optimized fashion, i.e. to resolve without involving a MessageFormat.
  <p>The default implementation <i>does</i> use MessageFormat, through
  delegating to the {@link #resolveCode} method. Subclasses are encouraged
  to replace this with optimized resolution.
  <p>Unfortunately, {@code java.text.MessageFormat} is not implemented
  in an efficient fashion. In particular, it does not detect that a message
  pattern doesn't contain argument placeholders in the first place. Therefore,
  it is advisable to circumvent MessageFormat for messages without arguments.
  
  @param code the code of the message to resolve
  @param locale the Locale to resolve the code for (subclasses are encouraged to support internationalization)
  @return the message String, or {@code null} if not found
  @see #resolveCode #resolveCode
  @see java.text.MessageFormat