MainActivity.java

@Override
public boolean onPrepareOptionsMenu(Menu menu) {
  setCount(this, "9");
}
    
public void setCount(Context context, String count) {
    MenuItem menuItem = defaultMenu.findItem(R.id.ic_group);
    LayerDrawable icon = (LayerDrawable) menuItem.getIcon();

    CountDrawable badge;

    // Reuse drawable if possible
    Drawable reuse = icon.findDrawableByLayerId(R.id.ic_group_count);
    if (reuse != null && reuse instanceof CountDrawable) {
        badge = (CountDrawable) reuse;
    } else {
        badge = new CountDrawable(context);
    }

    badge.setCount(count);
    icon.mutate();
    icon.setDrawableByLayerId(R.id.ic_group_count, badge);
}