hollow/src/main/java/com/netflix/hollow/core/read/engine/HollowReadStateEngine.java
public void addTypeListener(String typeName, HollowTypeStateListener listener) {
        List<HollowTypeStateListener> list = listeners.get(typeName);
        if(list == null) {
            list = new ArrayList<HollowTypeStateListener>();
            listeners.put(typeName, list);
        }

        list.add(listener);

        HollowTypeReadState typeState = typeStates.get(typeName);
        if(typeState != null)
            typeState.addListener(listener);
    }
public void addTypeListener(String typeName, HollowTypeStateListener listener) {
        List<HollowTypeStateListener> list = listeners.get(typeName);
        if(list == null) {
            list = new ArrayList<HollowTypeStateListener>();
            listeners.put(typeName, list);
        }

        list.add(listener);

        HollowTypeReadState typeState = typeStates.get(typeName);
        if(typeState != null)
            typeState.addListener(listener);
    }
Add a {@link HollowTypeStateListener} to a type.

@param typeName the type name
@param listener the listener to add