Java CheckboxMenuItem get/setState

I am using this to create a quick menu in my Java system tray app.

    Menu notiSET = new Menu("Benachrichtigungen");
    CheckboxMenuItem ns1 = new CheckboxMenuItem("On");
    CheckboxMenuItem ns2 = new CheckboxMenuItem("Off");

I would like to set Checkbox ns1 to true by default.

Using ns1.setState(true); doesnt work - I can only change the state by clicking it.

I tried using .setSelected(); or isSelected(); which doesnt work as well (methods not known).

What am I doing wrong?