MessageManager { protected String getStringOrNull(ResourceBundle bundle, String key) { if (bundle == null) { return null; } if (key == null) { if (throwIfResourceNotFound) { throw new MessageRuntimeException("key is null"); } return null; } try { return bundle.getString(key); } catch (MissingResourceException e) { return null; } } MessageManager(String configFile);  MessageManager(String configFile, String messageIdFormatKey,
                          String messageBaseNameKey,
                          String throwIfResourceNotFoundKey,
                          String messageFormatterFqcnKey); String getMessage(boolean resource, String messageIdOrPattern,
            Object... args); String getMessage(boolean resource, String messageIdOrPattern,
            Locale locale, Object... args);  }
@Test public void testGetStringOrNull01() { MessageManager manager = new MessageManager("jp/terasoluna/fw/message/terasoluna-logger02.properties"); assertNull(manager.getStringOrNull(null, null)); }