Stack in android

it's first time for me I use java I need to use a stack in android funcions but if I define the stack out of the function give me the error (should be parametrized) and the application crashes

public class Televideo extends Activity{
    Stack pila = new Stack();

    @Override
    public void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        pila.push(mystring);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item){
        mys开发者_如何学Gotring = pila.peek();
    }
}

how can I use the stack through class functions in java? thanks

parametrising means that you tell the Class (in this case your Stack) what type of objects its instance (in this case pila) will contain. Try this code instead of yours:

Stack<String> pila = new Stack<String>()

However, this should not be an error but only a warning as far as I know.