Java Foundation Classes in a Nutshell

component is centered. Other values position the component appropriately

between these positions. When a

Box needs to position a component vertically in

arow, it uses the component’s

alignmentY pr operty to place the component in the

vertical plane in an analogous way.

Simple Dialogs

GUIs often use dialog boxes to handle simple interactions with the user.

javax.swing.JOptionPane is a Swing component that is designed to serve as a

highly configurable body of a dialog box. Instead of using the

JOptionPane

dir ectly, however, most Swing programs use one or more of the many static meth-

ods defined by

JOptionPane. These methods make it quite easy to implement sim-

ple dialog-based interactions.

If you take a look at the API for

JOptionPane, you’ll see that the class defines a

gr oup of static methods whose names begin with

show and another whose names

begin with

showInternal. The show methods display simple dialog boxes within

JDialog windows, while the showInternal methods display the same dialog boxes

inside

JInternalFrame windows. These static methods are further broken down by

the type of dialog they display. There are several versions of

showMessageDia-

log(), showConfirmDialog(), and showInputDialog(),aswell as showInternal

versions of the same methods. We’ll consider these three types of dialogs—mes-

sage, confirm, and input—in the sections that follow.

Message Dialogs

Message dialogs are used to display important ...