Generics Java News Aggregator

package generics.aggregator;

import java.lang.reflect.ParameterizedType;
import java.math.BigDecimal;
import java.util.HashMap;
import java.util.Set;

public class GenericObserver {

    public static abstract class News {
        public abstract String getHeader();
    }

    public static abstract class SportsNews extends News {
        abstract String getWinner();
    }

    public static abstract class FinancialNews extends News {
        abstract BigDecimal getStockPrice();
    }

    public static void main(String[] args) {
        Aggregator aggregator = new Aggregator();

        Subscriber<FinancialNews> financialReader = new Subscriber<FinancialNews>(){

            @Override
            public void onNews(FinancialNews news) {
                System.out.println(String.format("%s%nStock price: $%d%n%n",
                        news.getHeader(), news.getStockPrice()));
            }

        };

        Subscriber<SportsNews> sportsReader = new Subscriber<SportsNews>() {

            @Override
            public void onNews(SportsNews news) {
                System.out.println(news.getWinner());
            }

        };

        aggregator.subscribe(financialReader);
        aggregator.subscribe(sportsReader);

        aggregator.dispatch(new FinancialNews(){

            @Override
            public String getHeader() {
                return "Zuckerberg sells 100k stock options";
            }

            @Override
            public BigDecimal getStockPrice() {
                return new BigDecimal("10.28");
            }
        });


    }

    public static class Aggregator {

        private HashMap<Class<?>, Set<Subscriber<? extends News>>> subscriptions;

        public <N extends News> void subscribe(Subscriber<N> subscriber) {
            ParameterizedType pt = (ParameterizedType) subscriber.getClass().getGenericSuperclass();
            Class<? extends News> klass = (Class<? extends News>) pt.getActualTypeArguments()[0];
            getSubscribersFor(klass).add(subscriber);
        }

        public <N extends News> void dispatch(N news) {
            for (Subscriber<N> subscriber: getSubscribersFor(news.getClass())) {
                subscriber.onNews(news);
            }
        }

        private <N extends News> Set<Subscriber<N>> getSubscribersFor(Class<N> klass) {
            //Set<Subscriber<N>> subscribers = subscriptions.get(news.getClass());
            //return subscribers;
            return null;
        }
    }

    public static interface Subscriber<N extends News> {
        public void onNews(N news);
    }

}