Create an application with a square window Using Swing Part 2

 Add six buttons to the application in the Following example in a vertical column on the left side of the application window.

Create an application with a square window Using Swing Part 1

Modification of this example is highlighted Here

import javax.swing.JFrame;
import javax.swing.SwingUtilities;
import javax.swing.Box;
import javax.swing.JButton;
import java.awt.Toolkit;
import java.awt.Dimension;
import java.awt.BorderLayout;

@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
    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/");
            }
        });
   }
}

Output of Above Java Program