title: cannot find implementation for database Room
body: <p>I am writing my first application with Room. I discovered it has issues when it uses kotlin, even some sample doesn't work on my machine, so I rollback to plain Java. </p>
  
  <pre><code>FilmsDatabaseJ db = Room.databaseBuilder(getApplicationContext(), FilmsDatabase.class, "DATABASE_NAME").build();
  </code></pre>
  
  <p>This call fails with exception: </p>
  
  <pre><code>java.lang.RuntimeException: cannot find implementation for com.home.myapplication.films.storage.FilmsDatabase. FilmsDatabase_Impl does not exist
  </code></pre>
  
  <p>I explored source code, Room expects to have such class already (does generated somewhere?), but by some reason such class doesn't exist for my case which is not far from documentation. Could you please share your ideas what might went wrong here?</p>
  
  <pre><code>@TypeConverters({Converters.class})
  @Database(entities = {Film.class, User.class, UserFilms.class}, version = 1)
  public abstract class FilmsDatabaseJ extends RoomDatabase {
  
      private static final String DATABASE_NAME = "DATABASE_NAME";
  
      private static FilmsDatabaseJ instance;
  
      public abstract FilmsDaoJ getFilmsDao();
  
  
      @NotNull
      public static FilmsDatabaseJ getInstance(Context context) {
          if (instance == null) {
              synchronized (FilmsDatabaseJ.class) {
                  if (instance != null) return
                  instance = Room.databaseBuilder(context, FilmsDatabaseJ.class, DATABASE_NAME).build();
              }
          }
          return instance;
      }
  } 
  
  
  
     annotationProcessor "android.arch.lifecycle:compiler:1.1.1"
  
      // Room (use 1.1.0-beta2 for latest beta)
      implementation "android.arch.persistence.room:runtime:1.0.0"
      annotationProcessor "android.arch.persistence.room:compiler:1.0.0"
  </code></pre>