Vertx vertx = Vertx.vertx(new VertxOptions().
  setPreferNativeTransport(true)
);

// True when native is available
boolean usingNative = vertx.isNativeTransportEnabled();
System.out.println("Running with native: " + usingNative);
Note
preferring native transport will not prevent the application to execute (for example if a JAR is missing). If your application requires native transport, you need to check isNativeTransportEnabled.