public synchronized void addListener(AuthListener listener) {
        if (getListeners().contains(listener)){
            return;
        }
        mListeners.add(new WeakReference<>(listener));
    }
public synchronized void addListener ( AuthListener listener ) { if ( getListeners ( ) . contains ( listener ) ) { return ; } mListeners . add ( new WeakReference < > ( listener ) ) ; }
Add listener to listen to the authentication process for this BoxSession.
@param listener listener for authentication