JPanel fatPanel   = new JPanel();
  JPanel calPanel   = new JPanel();
  JPanel perPanel   = new JPanel();
  
  public percentFatPanel()   
  {  
    fatPanel.add( fatLabel );
    fatPanel.add( inFat );
    calPanel.add( calLabel );
    calPanel.add( inCal );
    perPanel.add( perLabel );
    perPanel.add( outPer );
    . . . .
  }

BoxLayout Layout Manager

Now add the top label, the three panels, and the button to the content pane. We want then to line up in a vertical column. FlowLayout would do this if the frame is not too wide. But we want it to be certain. For this, use BoxLayout. BoxLayout aligns components either horizontally or vertically. You pick the arrangement in the constructor:

BoxLayout(Container box, int axis) 

    box: the container this layout manager is for
            
    axis: BoxLayout.X_AXIS for left to right
          BoxLayout.Y_AXIS for top to bottom

The box field is a reference to the container (often the content pane of a JFrame) which the new layout manager is for.

public class percentFatPan extends JFrame implements ActionListener
{

  
  public percentFatPanel()   
  {  
    getContentPane().setLayout( 
        new BoxLayout( ________, ________ );  
   . . . . .