public enum LinkStates implements StuffDoneListener {

    ...

    DO_SOME_WORK {
        public void process() {
            ....
            ....
            someObject.startDoingSpecialStuff();
            outerClass.toState(WAIT_FOR_EVENT);
        }
    },


    WAIT_FOR_EVENT {
        public void process() {
            // does nothing
        }

        public void onSpecialStuffComplete() {

        }
    }

    ...

    // Default implementation of interface methods which individual states
    // may override at will
    public void onSpecialStuffComplete() {
    }

}