@Override
    public boolean add(String entry) {
        if (entry == null || innerSet.contains(entry.toLowerCase())) {
            return false;
        }

        innerSet.add(entry.toLowerCase());
        return super.add(entry);
    }
A simple case-insensitive linked hash map

@author Marc Savy {@literal <msavy@redhat.com>}
plugins/cors-policy/src/main/java/io/apiman/plugins/cors_policy/util/InsensitiveLinkedHashSet.java