GUIs - Multimedia Introduction to Programming Using Java - page 452

Vertical versus horizontal layout
Because the argument to the Box constructor is BoxLayout.X-AXIS , the line
of components is horizontal. If we change the argument to BoxLayout.Y_AXIS ,
the line of components is vertical, as shown in the center of Fig. 17.11.
A rectangular layout of buttons
Class Box and layout manager BoxLayout , together with the fact that we can
nest components, can be used to construct quite complex layouts. As an example
of this, we show code that, when placed in the constructor, produces the right-
most JFrame of Fig. 17.11, which looks like a rectangle of buttons.
First, create variable leftBox , store in it a vertical Box , and add three but-
tons to it:
Box leftBox= new Box(BoxLayout.Y_AXIS);
leftBox.add( new JButton(" 00 "));
leftBox.add( new JButton(" 01 "));
leftBox.add( new JButton(" 02 "));
Second, create a rightBox , store in it a vertical Box , and add three buttons
to it:
Box rightBox= new Box(BoxLayout.Y_AXIS);
rightBox.add( new JButton(" 10 "));
rightBox.add( new JButton(" 11 "));
rightBox.add( new JButton(" 12 "));
Third, create variable b , store in it a horizontal Box , and add boxes leftBox
and rightBox to it:
Box b= new Box(BoxLayout.X_AXIS);
b.add(leftBox);
b.add(rightBox);
Finally, add the labels and box b to the content pane and pack it:
Container cp= getContentPane();
cp.add( new JLabel(" north "), BorderLayout.NORTH);
cp.add( new JLabel(" south "), BorderLayout.SOUTH);
cp.add(b, BorderLayout.CENTER);
pack();
The ability to nest containers in other containers, together with the ability to
create horizontally or vertically placed components, makes it quite easy to con-
struct complex GUI designs.
Leaving spaces in a Box
Look at the JFrame on the right in Fig. 17.11. Suppose we do not want the
right middle button, but we do want the lower right button to remain at the bot-