Create an application with a square window Using Swing Part 4

Add another item to the Edit drop-down menu, which itself has a drop-down menu, and provide
 accelerators for the items in the menu.

import javax.swing.JFrame;
import javax.swing.SwingUtilities;
import javax.swing.Box;
import javax.swing.JButton;
import javax.swing.JMenuBar;
import javax.swing.JMenu;
import javax.swing.JMenuItem;
import javax.swing.KeyStroke;
import java.awt.Toolkit;
import java.awt.Dimension;
import java.awt.BorderLayout;
import static java.awt.event.InputEvent.CTRL_DOWN_MASK;

@SuppressWarnings("serial")
public class SquareWindow extends JFrame {
  public SquareWindow(String title) {
    super(title);

    Toolkit theKit = this.getToolkit();
    Dimension wndSize = theKit.getScreenSize();

    // Calculate window side length as half the screen height
    int size = wndSize.height/2;

    setBounds((wndSize.width - size)/2, (wndSize.height-size)/2,     // Position
                           size, size);              // Size
    addButtons();                              // Add the buttons to the window
    addMenu();                                // Add the menubar & menus
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    setVisible(true);
  }

  // Creates and adds the buttons to the content pane
  public void addButtons() {
      Box vBox = Box.createVerticalBox();  // Create a box to hold the buttons

      vBox.add(Box.createVerticalStrut(10));     // Start with a strut for spacing
      vBox.add(Box.createVerticalGlue());        // then glue

      // Add the buttons separated by glue
      JButton button = null;;
      for(int i = 1 ; i <= 6 ; i++) {
        vBox.add(button = new JButton("Button" + i));
        vBox.add(Box.createVerticalGlue());
      }
      vBox.add(Box.createVerticalStrut(10));    // Add a strut for end spacing

      // Content pane has BorderLayout by default - add vBox to the WEST
      getContentPane().add(vBox, BorderLayout.WEST);
   }

   public static void main(String[] args) {
    SwingUtilities.invokeLater(new Runnable() {
            public void run() {
              SquareWindow myWindow = new SquareWindow("http://java-programs"
                              +"-examples.blogspot.com/");
            }
        });
   }

   // Create and add a  menubar
   private void addMenu() {
      JMenuBar menuBar = new JMenuBar();       // Create the menubar

      // Create the menu headings
      JMenu fileMenu = new JMenu("File");
      JMenu editMenu = new JMenu("Edit");
      JMenu windowMenu = new JMenu("Window");
      JMenu helpMenu = new JMenu("Help");

      // Create menu items to the Edit menu
      JMenuItem cut = new JMenuItem("Cut");
      JMenuItem copy = new JMenuItem("Copy");
      JMenuItem paste = new JMenuItem("Paste");
      JMenuItem selectAll = new JMenuItem("Select All");

      // Create Accelerators
      cut.setAccelerator(KeyStroke.getKeyStroke('X', CTRL_DOWN_MASK));
      copy.setAccelerator(KeyStroke.getKeyStroke('C', CTRL_DOWN_MASK));
      paste.setAccelerator(KeyStroke.getKeyStroke('V', CTRL_DOWN_MASK));
      selectAll.setAccelerator(KeyStroke.getKeyStroke('A', CTRL_DOWN_MASK));

      // Add menu items to the edit menu
      editMenu.add(cut);
      editMenu.add(copy);
      editMenu.add(paste);
      editMenu.addSeparator();
      editMenu.add(selectAll);

      // Create a dropdown menu within the edit dropdown menu
      JMenu findMenu = new JMenu("Find...");
      JMenuItem findInPage = new JMenuItem("In this page");
      JMenuItem findInDoc = new JMenuItem("In the document");
      findInPage.setAccelerator(KeyStroke.getKeyStroke('P', CTRL_DOWN_MASK));
      findInDoc.setAccelerator(KeyStroke.getKeyStroke('D', CTRL_DOWN_MASK));
      findMenu.add(findInPage);
      findMenu.add(findInDoc);
      editMenu.addSeparator();
      editMenu.add(findMenu);

      menuBar.add(fileMenu);
      menuBar.add(editMenu);
      menuBar.add(windowMenu);
      menuBar.add(helpMenu);

      setJMenuBar(menuBar);     // Add the menubar to the window
   }
}

Output of Above Java Program