public class UpdateFinalField {
    final int f;
    final Runnable updater;

    UpdateFinalField() {
        updater = () -> { f = 1; };
        f = 0;
    }

    public static void main(String[] args) {
        UpdateFinalField u = new UpdateFinalField();
        System.out.println("u.f = " + u.f);
        u.updater.run();
        System.out.println("u.f = " + u.f);
    }
}