Setting BoxLayout for a JFrame

Recall that to set the layout manager of a container to BoxLayout you need to include a reference to the container in the constructor:

BoxLayout(Container contain, int axis) 

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

A problem with doing this with a JFrame is that the container that holds the GUI components is the content pane of the frame. (JFrame are made up of several components, which you usually don't need to worry about.) To get a reference to the content pane use the getContentPane() method of the frame. Here is how you could change the layout manager of the frame of the previous example:

    setLayout( new BoxLayout( getContentPane(), BoxLayout.Y_AXIS ); 
    add( dataPanel );
    add( butPanel );

This would have no visible effect in the example program unless the size of the frame were made much wider. A wide frame using FlowLayout would arrange dataPanel and butPanel horizontally. A wide frame using BoxLayout would arrange dataPanel and butPanel vertically.