setting up a empty class as a container java code example

Example: BoxLayout java

JScrollPane listScroller = new JScrollPane(list);
listScroller.setPreferredSize(new Dimension(250, 80));
listScroller.setAlignmentX(LEFT_ALIGNMENT);
...
//Lay out the label and scroll pane from top to bottom.
JPanel listPane = new JPanel();
listPane.setLayout(new BoxLayout(listPane, BoxLayout.PAGE_AXIS));
JLabel label = new JLabel(labelText);
...
listPane.add(label);
listPane.add(Box.createRigidArea(new Dimension(0,5)));
listPane.add(listScroller);
listPane.setBorder(BorderFactory.createEmptyBorder(10,10,10,10));

//Lay out the buttons from left to right.
JPanel buttonPane = new JPanel();
buttonPane.setLayout(new BoxLayout(buttonPane, BoxLayout.LINE_AXIS));
buttonPane.setBorder(BorderFactory.createEmptyBorder(0, 10, 10, 10));
buttonPane.add(Box.createHorizontalGlue());
buttonPane.add(cancelButton);
buttonPane.add(Box.createRigidArea(new Dimension(10, 0)));
buttonPane.add(setButton);

//Put everything together, using the content pane's BorderLayout.
Container contentPane = getContentPane();
contentPane.add(listPane, BorderLayout.CENTER);
contentPane.add(buttonPane, BorderLayout.PAGE_END);