code: public void start() throws IllegalStateException {
          Log.d(TAG, "start");
  
          if (mediaPlayer != null) {
              currentState = State.STARTED;
              mediaPlayer.setOnCompletionListener(this);
              mediaPlayer.start();
          } else throw new RuntimeException("Media Player is not initialized");
      }
docs: MediaPlayer method (start)
  
  @see <a href="http://developer.android.com/reference/android/media/MediaPlayer.html#start%28%29">start</a>