import io.reactivex.Observable;
import retrofit2.http.GET;

public interface APIService
{
    @GET("application/json")
    Observable<List<NewsFeed>> getProductData();
}

public class NewsFeed
{
    private String feed;

    public void setFeed(String feed)
    {
        this.feed = feed;
    }

    public String getFeed()
    {
        return feed;
    }

}

Gson gson = new GsonBuilder()
                .setLenient()
                .create();

        Retrofit retrofit = new Retrofit.Builder()
                .baseUrl(url)
                .addConverterFactory(GsonConverterFactory.create(gson))
                .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
                .build();
        APIService apiService = retrofit.create(APIService.class);