Java JMenuItem(Action a) Constructor

public JMenuItem(Action a)

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
/*from   w w w.j a v a 2 s . c  o m*/
import javax.swing.AbstractAction;
import javax.swing.Action;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JPanel;
import javax.swing.JToolBar;

public class Main {

  public static void main(String args[]) {
    JFrame frame = new JFrame("Action Sample");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    final Action printAction = new PrintHelloAction();

    JMenuBar menuBar = new JMenuBar();
    JMenu menu = new JMenu("File");
    menuBar.add(menu);
    menu.add(new JMenuItem(printAction));

    JToolBar toolbar = new JToolBar();
    toolbar.add(new JButton(printAction));

    JButton enableButton = new JButton("Enable");
    ActionListener enableActionListener = new ActionListener() {
      public void actionPerformed(ActionEvent actionEvent) {
        printAction.setEnabled(true);
      }
    };
    enableButton.addActionListener(enableActionListener);

    JButton disableButton = new JButton("Disable");
    ActionListener disableActionListener = new ActionListener() {
      public void actionPerformed(ActionEvent actionEvent) {
        printAction.setEnabled(false);
      }
    };
    disableButton.addActionListener(disableActionListener);

    JButton relabelButton = new JButton("Relabel");
    ActionListener relabelActionListener = new ActionListener() {
      public void actionPerformed(ActionEvent actionEvent) {
        printAction.putValue(Action.NAME, "Hello, World");
      }
    };
    relabelButton.addActionListener(relabelActionListener);

    JPanel buttonPanel = new JPanel();
    buttonPanel.add(enableButton);
    buttonPanel.add(disableButton);
    buttonPanel.add(relabelButton);

    frame.setJMenuBar(menuBar);

    frame.add(toolbar, BorderLayout.SOUTH);
    frame.add(buttonPanel, BorderLayout.NORTH);
    frame.setSize(300, 200);
    frame.setVisible(true);

  }

}

class PrintHelloAction extends AbstractAction {

  PrintHelloAction() {
    super("Print");
    putValue(Action.SHORT_DESCRIPTION, "Hello, World");
  }

  public void actionPerformed(ActionEvent actionEvent) {
    System.out.println("Hello, World");
  }
}