Hello guys, please I need help. I have develoed an application using net bean,

1) I'm making project in java API 6. I'm using "Net Beans 7.1".
2) I want to use "JInternalFrame" in my project
3) I made another package and made "JInternalFrame" there. And then call it in my main application window by firing action performed event on "JMenuItem".
4) It works fine but only one problem occurs that is, if i click on "JMenuItem" again and again, new "JInternalFrame" of same instance are opening, How can i stop that?
5) I want that, if I open "JInternalFrame" once and then i again click on "JMenuItem" to open the same "JInternalFrame", it Should do nothing or it shows the window which already opened and minimized.

sample code:
private void empDataActionPerformed(java.awt.event.ActionEvent evt) {

Emps employees = new Emps();
Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
employees.setBounds(230, 40, screenSize.width / 2 - 80, screenSize.height / 2 + 105);

Thanks In Advance!