public class percentFatPan extends JFrame implements ActionListener
{
  public percentFatPanel()   
  {  
    getContentPane().setLayout( 
        new BoxLayout( getContentPane(), BoxLayout.Y_AXIS ); 
         
    . . . . .
Two uses of getContentPane() are needed to set
the layout manager:
getContentPane() gets the content pane whose layout manager is to be set.getContentPane() send a reference to the content pane to BoxLayout.Now add the top label, the panels, and the button to the content pane:
Add the components from top to bottom