# Quick Start

You have your REST API ready to serve JSON in less than ten lines of code

    What is ctx -> HttpResponse.of("Pong") ?

    This is called Functional Interface(opens new window) - a shorthand syntax of Java 8, if you use Java 7 and before, you can write like this:

    server.use("/", new Handler() {
        public HttpResponse handleFunc(Context context) throws Exception {
            return HttpResponse.of("Hello World!");
    Okay, then what is gson::toJson ?

    It's another sugar syntax called Double Colon Operator(opens new window)

    The code above can be written without Double Colon Operator like this:

    server.useTransformer(response -> gson.toJson(response));

    or without Double Colon Operator and Functional Interface should be as follows:

    server.useTransformer(new RequestTransformer() {
        public String render(Object model) {
            return gson.toJson(model);