Mnemonic on JMenuItem

Question

I'm lost. Any idea why alt+a shortcut for my JMenuItem doesn't work?
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import javax.swing.AbstractAction;
import javax.swing.JFrame;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
public class MainClass {
  public static void main(String[] a) {
    JFrame frame = new JFrame();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    JMenuBar menu = new JMenuBar();
    menu.add(new JMenuItem(new ShowAction()));
    frame.add(menu);
    frame.setSize(350, 150);
    frame.setVisible(true);
class ShowAction extends AbstractAction {
  public ShowAction() {
     super("fire!");
    putValue(MNEMONIC_KEY, new Integer(KeyEvent.VK_A));
  public void actionPerformed(ActionEvent actionEvent) {
    System.out.println("fired");
}

Answer 1

1) The mnemonic should be a character in the menu item text, maybe VK_F.
2) a JMenuItem is added to a JMenu which is added to a JMenuBar, which is added to the frame by using frame.setJMenuBar(...). Read the section from the Swing tutorial on [url http://download.oracle.com/javase/tutorial/uiswing/components/menu.html]How to Use Menus.
3) Then the mnemonic is activated only when the menu is opened.
Maybe you really want to use an "accelerator", which allows you to invoke the Action without opening the menu.
Or you can use "Key Bindings". The tutorial link from above also has a section on this topic.