@SuppressWarnings("unchecked")
    public void addLoader(final Class<? extends AssetLoader> loaderType, String ... extensions) {
        // Synchronized access must be used for any ops on classToLoaderMap
        ImplThreadLocal local = new ImplThreadLocal(loaderType, extensions);
        for (String extension : extensions) {
            extension = extension.toLowerCase();
            synchronized (classToLoaderMap) {
                classToLoaderMap.put(loaderType, local);
                extensionToLoaderMap.put(extension, local);
            }
        }
    }
Returns the AssetLoader registered for the given extension
of the current thread.
@return AssetLoader registered with addLoader.
jme3-core/src/main/java/com/jme3/asset/ImplHandler.java