import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpResponse;
import java.time.Duration;
import java.util.concurrent.CompletableFuture;

public class SimpleTimeoutTest {

    public static void main(String[] args) throws Exception {
        String uri = "..."; // a long time access
        HttpClient client = HttpClient.create().build();
        CompletableFuture<HttpResponse<String>> responseFC = client
                .request(new URI(uri)).timeout(Duration.ofSeconds(1)).GET()
                .responseAsync(HttpResponse.BodyHandler.asString());
        System.out.println(responseFC.join().body());
    }
}

The above test doesn't throw HttpTimeoutException and cannot finish.