/* check if all provided resources are package resources */
private void checkProvidedResources()
{
for (T curProvidedResource : providedResources)
{
ResourceReference reference = curProvidedResource.getReference();
if (!(reference instanceof CssResourceReference || reference instanceof JavaScriptResourceReference))
{
throw new IllegalArgumentException(
"ConcatResourceBundleReference only works with CssResourceReference and JavaScriptResourceReference, " +
curProvidedResource + " provides a " +
reference.getClass().getSimpleName());
}
}
}