Unsupported operation: Android, Retrofit, OkHttp. Adding interceptor in OkHttpClient

I am trying to add token based authentication via Retrofit 2.0-beta3 and OkHttpClient in Android using interceptors. But I get UnsupportedOperationException when I add my interceptor in OkHttpClient. Here is my code: In ApiClient.java

public static TrequantApiInterface getClient(final String token) {
        if( sTreqantApiInterface == null) {

            Log.v(RETROFIT_LOG, "Creating api client for the first time");
            OkHttpClient okClient = new OkHttpClient();

            okClient.interceptors().add(new Interceptor() {
                @Override
                public Response intercept(Interceptor.Chain chain) throws IOException {
                    Request original = chain.request();

                    // Request customization: add request headers
                    Request.Builder requestBuilder = original.newBuilder()
                            .header("Authorization", token)
                            .method(original.method(), original.body());

                    Request request = requestBuilder.build();
                    return chain.proceed(request);
                }
            });

            Retrofit client = new Retrofit.Builder()
                    .baseUrl(baseUrl)
                    .client(okClient)
                    .addConverterFactory(GsonConverterFactory.create())
                    .build();
            sTreqantApiInterface = client.create(TrequantApiInterface.class);
        }
        return sTreqantApiInterface;
    }

And I use it like:

private void ampFreqTest(){
    String token = getSharedPreferences(getString(R.string.preference_file_key), Context.MODE_PRIVATE)
                        .getString(getString(R.string.key_token), "");

    service = ApiClient.getClient(token);
    //I get an exception on this line:
    Call<List<AmpFreq>> call = service.getUserAmpFreq("1");
    call.enqueue(new Callback<List<AmpFreq>>() {
        @Override
        public void onResponse(Response<List<AmpFreq>> response) {
            Toast.makeText(HomeScreen.this, "Got result", Toast.LENGTH_LONG);

            Log.v(ApiClient.RETROFIT_LOG, "Success api client." + response.message());
            Log.v(ApiClient.RETROFIT_LOG, "Success api client.");
        }
        @Override
        public void onFailure(Throwable t) {
            Toast.makeText(HomeScreen.this, t.getMessage() , Toast.LENGTH_LONG);
            Log.v(ApiClient.RETROFIT_LOG, "Fail api client." + t.getMessage() );
        }
    });
}

But I get this error:

Process: com.trequant.usman.trequant_android, PID: 14400
java.lang.UnsupportedOperationException at java.util.Collections$UnmodifiableCollection.add(Collections.java:932)
 at com.trequant.usman.trequant_android.api.ApiClient.getClient(ApiClient.java:41)

It gives me error on adding a new interceptor saying that it is not modifiableCollection but the documentation for interceptors() function says: /**

   * Returns a modifiable list of interceptors that observe the full span of each call: from before
   * the connection is established (if any) until after the response source is selected (either the
   * origin server, cache, or both).
   */

What am I doing wrong? Could it be a bug?

This issue occurs when you change Retrofit 2.0-beta2 to Retrofit 2.0-beta3. You have to use builder if you want to create OkHttpClient object.

Change :

 OkHttpClient okClient = new OkHttpClient();

 okClient.interceptors().add(new Interceptor() {
       @Override
       public Response intercept(Interceptor.Chain chain) throws IOException {
            Request original = chain.request();

            // Request customization: add request headers
            Request.Builder requestBuilder = original.newBuilder()
                    .header("Authorization", token)
                    .method(original.method(), original.body());

            Request request = requestBuilder.build();
            return chain.proceed(request);
        }
 });

to :

 OkHttpClient okClient = new OkHttpClient.Builder()
           .addInterceptor(
               new Interceptor() {
                 @Override
                 public Response intercept(Interceptor.Chain chain) throws IOException {
                       Request original = chain.request();

                       // Request customization: add request headers
                       Request.Builder requestBuilder = original.newBuilder()
                               .header("Authorization", token)
                               .method(original.method(), original.body());

                       Request request = requestBuilder.build();
                       return chain.proceed(request);
                   }
               })
           .build();

It should resolve your problem.

Try this if the other answer doesn't work:

OkHttpClient okHttpClient = new OkHttpClient.Builder()
    .addInterceptor(new MyInterceptor())
    .build();
retrofit = new Retrofit.Builder()
    .baseUrl("http://google.com")
    .addConverterFactory(GsonConverterFactory.create())
    .client(okHttpClient)
    .build();

You Can Add In this way also.

HttpLoggingInterceptor interceptor = new HttpLoggingInterceptor();
interceptor.setLevel(HttpLoggingInterceptor.Level.BODY);
OkHttpClient client = new OkHttpClient.Builder().addInterceptor(interceptor).build();

 Retrofit retrofit = new Retrofit.Builder()
            .baseUrl("ENDPOINT_URL")
            .addConverterFactory(GsonConverterFactory.create()).client(client)
            .build();