Android Button or ImageButton Click Using Implements onclickListener

public class Aboutus extends Activity implements OnClickListener {
private ImageButton back;
@Override
public void onCreate(Bundle savedInstanceState) {
   super.onCreate(savedInstanceState);
     setContentView(R.layout.aboutus);
            back=(ImageButton)findViewById(R.id.header_left_btn);
              back.setOnClickListener(this);
}
public void onClick(View arg0) {

if(arg0==back)
{
finish();
}
}

}