Websocket onMessage with a callback and then using JDK 8 CompletableFuture

CallbackA.java

public interface Callback<T> {

    public void call(T value);
}

import java.io.Console;

public class ConsoleTask implements Runnable  {

    Console console;
    private final Callback<String> callback;    
    
    public ConsoleTask(Callback<String> callback) {
        this.callback = callback;
    }

    @Override
    public void run() {
        console = System.console();
        if (console == null) {
            callback.call("No console.");
        }
        String msg = console.readLine();
        callback.call(msg);
    }

}

@OnMessage
public void onMessage(Session session, Message message) {
    System.out.println("Received: '" + message.getMessage() + "'");
    if (latch.getCount() == 0) {
        latch = new CountDownLatch(1);
        executor.execute(new ConsoleTask(new Callback<String>() {

            @Override
            public void call(String msg) {
                try {
                    session.getBasicRemote().sendObject(new Message(writeJson(msg)));
                } catch (IOException | EncodeException e) {
                    logger.debug(e.getMessage());
                }
                latch.countDown();
            }
        }));
    }
    System.out.print("Enter a message: ");
}

CompletableFutureB.java

import java.io.Console;
import java.util.function.Supplier;

public class ConsoleTask<T> implements Supplier<String>  {

    Console console;
  
    @Override
    public String get() {
        console = System.console();
        if (console == null) {
            return "No console.";
        }
        String msg = console.readLine();
        return msg;
    }

}

@OnMessage
public void onMessage(Session session, Message message) {
    System.out.println("Received: '" + message.getMessage() + "'");
    if (latch.getCount() == 0) {
        latch = new CountDownLatch(1);
        ConsoleTask<String> task = new ConsoleTask<String>();
        CompletableFuture.supplyAsync(task, executor).thenAcceptAsync(msg -> {
            try {
                session.getBasicRemote().sendObject(new Message(writeJson(msg)));
            } catch (IOException | EncodeException e) {
                logger.debug(e.getMessage());
            }
            latch.countDown();
        }, executor);
    }
    System.out.print("Enter a message: ");
}