AppBaseService.java

public class AppBaseService {

    private static final AppBaseService ourInstance = new AppBaseService();
    private static String BASE_URL = "https://en.wikipedia.org/";
  
    private Retrofit retrofit;

    private final static OkHttpClient okHttpClient = new OkHttpClient.Builder()
            .readTimeout(2, TimeUnit.MINUTES)
            .connectTimeout(2, TimeUnit.MINUTES)
            .build();

    public static AppBaseService getInstance() {
        return ourInstance;
    }

    private AppBaseService() {
        retrofit = new Retrofit.Builder()
          .baseUrl(BASE_URL)
          .client(okHttpClient)
          .addConverterFactory(GsonConverterFactory.create())
          .build();
    }
    
    public WikipediaService getWikiService() {
        return retrofit.create(WikipediaService.class);
    }
}