// JFace guarantees that TableViewers always provide a structured selection
IStructuredSelection selectedElementKinds = getSelection();
Collection<Class<? extends Element>> result = Lists.newArrayList();
for(Object obj : selectedElementKinds.toList()) {
ElementKindDescriptor item = (ElementKindDescriptor) obj;
result.add(item.getElementKind());
}
return result;
}