private List<DocumentType> getDocumentTypes(final Collection<String> visibleTypes) {
        return getTypes().stream()
                .filter(type -> visibleTypes.contains(type.getType()))
                .collect(Collectors.toList());
    }
Create a map of folders and their child items.
stroom-explorer/stroom-explorer-impl/src/main/java/stroom/explorer/impl/ExplorerServiceImpl.java