code: @Override
      public final void clear()
      {
          fireEvent(EVENT_CLEAR, null, null, true);
          configList.clear();
          namedConfigurations.clear();
          // recreate the in memory configuration
          containerConfiguration = new ConcurrentMapConfiguration();
          containerConfiguration.setThrowExceptionOnMissing(isThrowExceptionOnMissing());
          containerConfiguration.setListDelimiter(getListDelimiter());
          containerConfiguration.setDelimiterParsingDisabled(isDelimiterParsingDisabled());
          containerConfiguration.addConfigurationListener(eventPropagater);
          configList.add(containerConfiguration);
          
          overrideProperties = new ConcurrentMapConfiguration();
          overrideProperties.setThrowExceptionOnMissing(isThrowExceptionOnMissing());
          overrideProperties.setListDelimiter(getListDelimiter());
          overrideProperties.setDelimiterParsingDisabled(isDelimiterParsingDisabled());
          overrideProperties.addConfigurationListener(eventPropagater);
          
          fireEvent(EVENT_CLEAR, null, null, false);
          containerConfigurationChanged = false;
          invalidate();
      }
docs: Removes all child configurations and reinitializes the <em>container
  configuration</em>. <strong>Attention:</strong> A new container
  configuration is created; the old one is lost.