Can you explain what Retrofit Client is and how it is used for interacting with REST API?

Retrofit Client is a library for Android and Java that simplifies interaction with REST APIs. It allows you to create HTTP requests to a server and receive responses, automatically converting JSON or XML into Java objects.

Main features:

• Uses annotations to describe HTTP methods (GET, POST, PUT, etc.).
• Supports converters for data serialization/deserialization (e.g., Gson).
• Enables working with asynchronous and synchronous requests.

Example usage:

public interface ApiService {
    @GET("users/{id}")
    Call<User> getUser(@Path("id") int userId);
}

Retrofit retrofit = new Retrofit.Builder()
    .baseUrl("https://api.example.com/")
    .addConverterFactory(GsonConverterFactory.create())
    .build();

ApiService service = retrofit.create(ApiService.class);
Call<User> call = service.getUser(1);
call.enqueue(new Callback<User>() {
    @Override
    public void onResponse(Call<User> call, Response<User> response) {
        if (response.isSuccessful()) {
            User user = response.body();
            // handle the received user
        }
    }

    @Override
    public void onFailure(Call<User> call, Throwable t) {
        // handle error
    }
});

Thus, Retrofit significantly simplifies working with REST APIs, making the code cleaner and easier to maintain.