archaius-core/src/main/java/com/netflix/config/PropertyWrapper.java
@Override
    public void addCallback(Runnable callback) {
        if (callback != null) {
            prop.addCallback(callback);
            callbacks.add(callback);
        }
    }
@Override
    public void addCallback(Runnable callback) {
        if (callback != null) {
            prop.addCallback(callback);
            callbacks.add(callback);
        }
    }
Add the callback to be triggered when the value of the property is changed

@param callback