Since the Lightstreamer Client API is asynchronous, blocking its threads can have unexpected results.
However you can set a timeout by using a java.util.Timer (or equivalent asynchronous mechanism).
For example:

Code:
var client = new LightstreamerClient(...)
Timer timer = new Timer();
timer.schedule(() -> {
  if (!client.getStatus().startsWith("CONNECTED")) {
    client.disconnect();
  }
}, TIMEOUT);
client.connect();