public class Reactor implements Runnable {
    private final Selector selector;
    private final ServerSocketChannel serverSocketChannel;

    public Reactor(int port) throws IOException {
        selector = Selector.open();
        serverSocketChannel = ServerSocketChannel.open();
        serverSocketChannel.socket().bind(new InetSocketAddress(port));
        serverSocketChannel.configureBlocking(false);
        SelectionKey selectionKey = serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
        selectionKey.attach(new Acceptor());
    }

    @Override
    public void run() {
        try {
            while (!Thread.interrupted()) {
                selector.select();
                Set<SelectionKey> selectedKeys = selector.selectedKeys();
                Iterator<SelectionKey> it = selectedKeys.iterator();
                while (it.hasNext()) {
                    dispatch(it.next());
                    it.remove();
                }
            }
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }

    void dispatch(SelectionKey key) {
        Runnable r = (Runnable) (key.attachment());
        if (r != null) {
            r.run();
        }
    }

    class Acceptor implements Runnable {
        @Override
        public void run() {
            try {
                SocketChannel socketChannel = serverSocketChannel.accept();
                if (socketChannel != null) {
                    new Handler(selector, socketChannel);
                }
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }
    }
}