title: IllegalArgumentException: Could not locate call adapter for rx.Observable RxJava, Retrofit2
body: <p>I am getting the above error while calling the rest api. I am using both retrofit2 and RxJava.</p>
  
  <h2>ServiceFactory.java</h2>
  
  <pre><code>public class ServiceFactory {
  public static &lt;T&gt; T createRetrofitService(final Class&lt;T&gt; clazz, final String endpoint){
  
      Retrofit retrofit = new Retrofit.Builder()
              .baseUrl(endpoint)
              //.addConverterFactory(GsonConverterFactory.create())
  
              .build();
  
      T service = retrofit.create(clazz);
      return service;
  }
  </code></pre>
  
  <p>}</p>
  
  <h2>MovieService.java</h2>
  
  <pre><code>public interface MovieService{
  //public final String API_KEY = "&lt;apikey&gt;";
  public final String SERVICE_END = "https://api.mymovies.org/3/";
  @GET("movie/{movieId}??api_key=xyz")
  Observable&lt;Response&lt;Movies&gt;&gt; getMovies(@Field("movieId") int movieId);
  </code></pre>
  
  <p>}</p>
  
  <h1>Inside MainActivity</h1>
  
  <pre><code>      MovieService   tmdbService = ServiceFactory.createRetrofitService(MovieService.class, MovieService.SERVICE_END);
      Observable&lt;Response&lt;Movies&gt;&gt; responseObservable = tmdbService.getMovies(400);
      responseObservable .subscribeOn(Schedulers.newThread())
              .observeOn(AndroidSchedulers.mainThread())
              .subscribe(new Subscriber&lt;Response&lt;Movies&gt;&gt;() {
                  @Override
                  public void onCompleted() {
  
                  }
  
                  @Override
                  public void onError(Throwable e) {
  
                  }
  
                  @Override
                  public void onNext(Response&lt;Movies&gt; moviesResponse) {
  
                  }
              });
  </code></pre>