finish activity when back button twice pressed?

I am creating an application here i need to finish activity when user twice pressed back button. Here is my code what i tried

 @Override
public void onBackPressed() {
        super.onBackPressed();
        this.finish();
}

tried this too

 @Override
public boolean onKeyDown(int keyCode, KeyEvent event)
{
if ((keyCode == KeyEvent.KEYCODE_BACK))
{
    finish();
}
return super.onKeyDown(keyCode, event);
}

this helps me to finish activity once back button pressed.

Pls i need your suggestion. Thanks in advance