Android--Use of callback function

public class Callbacktools {    //interface Public    interface Onlistener {        void execute ();    }        Declaration interface    Onlistener CallBack;    Called, the execution interface implements public    void Calllisten () {        callback.execute ();    }    External interface Implementation public    void Setcallbacklistener (Onlistener listener) {        this.callback = listener;    }}

@Override    protected void onCreate (Bundle savedinstancestate) {        super.oncreate (savedinstancestate);        Setcontentview (r.layout.activity_main);        Final Callbacktools callbacktools = new Callbacktools ();        Callbacktools.setcallbacklistener (New Callbacktools.onlistener () {            @Override public            Void execute () {                // Do waht If this callback                is called LOG.E ("callback", "Success");}        );        Findviewbyid (R.id.button). Setonclicklistener (New View.onclicklistener () {            @Override public            void OnClick ( View v) {                callbacktools.calllisten ();}}        );    }

Android--Use of callback function