Re: How to align swing buttons vertically ?

They aligned as I'd expect:
- btnPanel is sized to contain the buttons and nothing else
  and is placed as you asked, on the east side of the content pane.
 
- The buttons have their centres aligned.

I don't understand what you mean by "not well aligned":

- If you want the buttons to appear as other than a close-packed block,
  take a look at "How to use BoxLayout" in the Java tutorial. It is also
  referenced from the the class description in the BoxLayout javadocs
  entry.

- If you want all buttons to be the same size, use a custom class in
  place of JButton:

import java.awt.*;
import javax.swing.*;

class MyButton extends JButton
{

   public MyButton(String label)
{
      super(label);

      Dimension d = new Dimension(120, 30);
      setMinimumSize(d);
      setMaximumSize(d);
      setPreferredSize(d);
   }
}