Method watch

java/lib/src/main/java/io/github/ccxt/Exchange.java:1684–1708

(Object url, Object messageHash2, Object message, Object subscribeHash2, Object subscription)

    }

    public CompletableFuture<Object> watch(Object url, Object messageHash2, Object message, Object subscribeHash2, Object subscription) {
        String messageHash = messageHash2.toString();
        String subscribeHash = subscribeHash2 != null ? subscribeHash2.toString() : messageHash;
        var client = this.client(url);

        io.github.ccxt.ws.Future future = client.future(messageHash);

        if (client.subscriptionsMap().putIfAbsent(subscribeHash, subscription != null ? subscription : true) == null) {
            client.connect(0).thenAccept(connected -> {
                if (message != null) {
                    try {
                        client.send(message);
                    } catch (Exception ex) {
                        client.subscriptionsMap().remove(subscribeHash);
                        future.reject(ex);
                    }
                }
            }).exceptionally(ex -> {
                client.subscriptionsMap().remove(subscribeHash);
                future.reject(ex);
                return null;
            });
        }
        return future.getFuture();
    }

    // Note: a single subscribe message is sent for all symbols, matching JS/C# design.
    // Exchange-specific code is responsible for building the message with all symbols.