Перевод кода с Kotlin на Java

Имею код на Kotlin (Android Studio 3.5):

Class RadioPlayerActivity : AppCompatActivity() {
private lateinit var player: SimpleExoPlayer
private lateinit var mediaSource: MediaSource
private lateinit var dataSourceFactory: DefaultDataSourceFactory
override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_radio_player)
    player = ExoPlayerFactory.newSimpleInstance(this)
    dataSourceFactory = DefaultDataSourceFactory(this, Util.getUserAgent(this, "OnAir"))
    mediaSource = ProgressiveMediaSource.Factory(dataSourceFactory).createMediaSource(Uri.parse(RADIO_URL))
    with(player) {
        prepare(mediaSource)
        btnStart.setOnClickListener {
            playWhenReady = true
        }
        btnStop.setOnClickListener {
            playWhenReady = false
        }
    }
}
override fun onDestroy() {
    player.playWhenReady = false
    super.onDestroy()
}
companion object {
    const val RADIO_URL = "http://s1.radioheart.ru:8001/radiogomelfm"

Переписываю на Java (Android Studio 3.5):

public class RadioPlayerActivity extends AppCompatActivity {
private SimpleExoPlayer player;
private DefaultDataSourceFactory dataSourceFactory;
private MediaSource mediaSource;
private Boolean playWhenReady;
static String RADIO_URL = "http://s1.radioheart.ru:8001/radiogomelfm";
@Override
protected void onCreate(Bundle savedInstanceState){
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_radio_player);
    playWhenReady = false;

    player = ExoPlayerFactory.newSimpleInstance(this);
    dataSourceFactory = new DefaultDataSourceFactory(this, Util.getUserAgent(this, "OnAir"));
    mediaSource = new ProgressiveMediaSource.Factory(dataSourceFactory).createMediaSource(Uri.parse(RADIO_URL));
}
public void OnStart(View view){
    player.prepare(mediaSource);
    playWhenReady = true;
}
public void OnStop(View view){
    playWhenReady = false;
}
}

В первом случае поток воспроизводится. В коде на Java - молчание. Что не так?