@SuppressWarnings("unchecked")
    private static Class<? extends ResourceLoader> findResourceLoaderClass(String className) {
        Class<?> clazz = null;

        try {
            clazz = Class.forName(className);
        } catch (final Throwable e) {
            LOGGER.log(Level.WARNING, "Unable to access {0}", className);
        }

        if (clazz != null && !ResourceLoader.class.isAssignableFrom(clazz)) {
            LOGGER.log(Level.WARNING, "{0} does not implement {1}", new Object[] { className, ResourceLoader.class.getName() });
            clazz = null;
        }

        return (Class<? extends ResourceLoader>) clazz;
    }
The property name to set the ResourceLoader to use. Should be set automatically
by the JmeSystemDelegate. 
Note: changing this property after the first use of the ResourceLoader will have no effect.
jme3-core/src/main/java/com/jme3/util/res/Resources.java