public ExtrasLoader getDefaultExtrasLoader() {
        if (defaultExtraLoaderClass == null) { 
            defaultExtraLoaderInstance = null; // do not hold reference
            return null;
        }

        if (defaultExtraLoaderInstance != null
                && defaultExtraLoaderInstance.getClass() != defaultExtraLoaderClass) {
            defaultExtraLoaderInstance = null; // reset instance if class changed
        }

        try {
            defaultExtraLoaderInstance = defaultExtraLoaderClass.getDeclaredConstructor().newInstance();
        } catch (Exception e) {
            logger.log(Level.WARNING, "Could not instantiate default extras loader", e);
            defaultExtraLoaderInstance = null;
        }

        return defaultExtraLoaderInstance;
    }
Returns the default extras loader.
@return the default extras loader.
jme3-plugins/src/gltf/java/com/jme3/scene/plugins/gltf/CustomContentManager.java