what inadequacy between controlling traveller settlement an interface?

what inadequacy between requesting traveller settlement pattern your formula following approach:

interface dointerface {
    open vacant perform(object o);
}

public category t {
    private dointerface d;
    private twine s;

    open twine gets() {
            relapse s;
    }

    open t(string s) {
            this.s = s;
    }

    open vacant setinterface(dointerface d) {
            this.d = d;
    }

    open vacant perform() {
            d.perform(this);
    }

    open stationary vacant main(string[] args) {
            t t = new t("geonline");
            t.setinterface(new dointerface() {
                    open vacant perform(object o) {
                            t = (t)o;
                            system.out.println(a.gets());
                    }
            });
            t.perform();
    }
}

i assume controlling interfaces, we're unequivocally separating algorithm.