public interface Transaction
{
  public void syncExec(Runnable runnable);
  public <V> V syncExec(Callable<V> callable) throws Exception;
}

public class SomeOtherClass
{
  private Transaction transaction;
  private boolean showMerges;

  public void close()
  {
    transaction.syncExec(new Runnable()
    {
      @Override
      public void run()
      {
        transaction.removeTransactionHandler(transactionHandler);
        transaction.removeListener(transactionListener);
      }
    });
  }

  public final void setShowMerges(final boolean showMerges)
  {
    transaction.syncExec(new Runnable()
    {
      @Override
      public void run()
      {
        SomeOtherClass.this.showMerges = showMerges;
      }
    });
  }
}

public class Notifier
{
  protected final void fireEvent(Event event)
  {
    for (Class<?> i : event.getClass().getInterfaces())
    {
      System.out.println(i);
    }
  }

  public interface Event
  {
    public Notifier getSource();
  }
}

public class SpecialNotifier extends Notifier
{
  public static void main(String[] args)
  {
    new SpecialNotifier().run();
  }

  public void run()
  {
    fireEvent(new SpecialEvent()
    {
      @Override
      public SpecialNotifier getSource()
      {
        return SpecialNotifier.this;
      }
    });
  }

  public interface SpecialEvent extends Event
  {
    @Override
    public SpecialNotifier getSource();
  }
}

interface events.SpecialNotifier$SpecialEvent

  public void run()
  {
    fireEvent(() -> SpecialNotifier.this);
  }

interface events.Notifier$Event

fireEvent((SpecialEvent)() -> SpecialNotifier.this);