BoxLayout.Y_AXIS has the following syntax.
public static final int Y_AXIS
In the following code shows how to use BoxLayout.Y_AXIS field.
/* w w w.jav a2 s . c o m*/ import java.awt.BorderLayout; import javax.swing.BoxLayout; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JPanel; public class Main { public static void main(String[] a) { JFrame frame = new JFrame("Alignment Example"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); String labels[] = { "--", "----", "--------", "------------" }; JPanel container = new JPanel(); BoxLayout layout = new BoxLayout(container, BoxLayout.Y_AXIS); container.setLayout(layout); for (int i = 0; i < labels.length; i++) { JButton button = new JButton(labels[i]); container.add(button); } frame.add(container, BorderLayout.CENTER); frame.setSize(300, 200); frame.setVisible(true); } }