Chickinnick

interface Base{
  fun foo()
}

class BI : Base{
  override fun foo() {

  }

}

Chickinnick

        //compiled successfully 
        MutableLiveData<BaseProduct> mutableLiveData  = new MutableLiveData<>();
        mutableLiveData.observe(this, new Observer<BaseProduct>() {
            @Override
            public void onChanged(@Nullable BaseProduct baseProduct) {

            }
        });