@Override
    protected Class<?> delegateClass(int id)
    {
        final RegisteredDelegate<?> rd = id < delegates.size() ? delegates.get(id) : null;
        return rd == null ? null : rd.delegate.typeClass();
    }
Register a {@link Delegate} and assign an id.
<p>
Delegate ids start at 1.
protostuff-runtime-registry/src/main/java/io/protostuff/runtime/IncrementalIdStrategy.java