### Question:
DefaultClientIdRegistry implements ClientIdRegistry { @Override public void printOn(Media media) { clientIdMapPerType.forEach((type, map) -> media.with(type.toString(), m -> map.forEach(m::with))); }  @Override boolean register(String clientStreamId, String clientId, ConnectionType type); @Override boolean unregister(String clientStreamId, ConnectionType type); @Override String clientId(String clientStreamId); @Override Set<String> streamIdsFor(String clientId, ConnectionType type); @Override void printOn(Media media); @EventListener void on(ApplicationConnected event); @EventListener void on(ApplicationDisconnected event); @EventListener void on(SubscribeCommand event); @EventListener void on(CommandHandlerDisconnected event); @EventListener void on(SubscribeQuery event); @EventListener void on(QueryHandlerDisconnected event);  }### Answer:
@Test public void printOn() { testSubject.register("clientStreamId", "clientId", ClientIdRegistry.ConnectionType.COMMAND); testSubject.register("clientStreamId2", "clientId", ClientIdRegistry.ConnectionType.QUERY); testSubject.register("clientStreamId3", "clientId", ClientIdRegistry.ConnectionType.PLATFORM); GsonMedia media = new GsonMedia(); testSubject.printOn(media); System.out.println(media); }