Java™ Application Development on Linux - Dator

16.3 Stompin’ at the Savoy, or The Swing Paradigm343While this may look like a lot of extra junk just to say “Hello, world,” rememberthat a GUI is not just providing output in fancy windows, but alsomonitoring and responding to a wide variety of user inputs—a capability ofwhich we make little or no use in this example. But you can see some of thisextra capability—grab the lower left corner of the window frame and expandand resize the window.16.3STOMPIN’ AT THE SAVOY, OR THE SWING PARADIGMWhen we say “Swing,” we generally mean the set of classes in the javax.swingpackage and its subpackages (such as javax.swing.table). The packages arelibraries of code that give you predefined classes from which you can constructa GUI for your application. The programs you write will be written in Java,the syntax will look like Java, but there will be a lot of creation of classes, usesof interfaces, implementations of abstract classes, and a variety of method callsthat all deal with these Swing classes.So what’s going on with all this stuff? What can we expect to do, see,write? In most applications that a programmer writes, it is the job of the programmerto design and write the code for the main execution path of the program.“Yes, every program has a beginning, middle, and an end” (with apologiesto “Seymour and his frozen yoghurt stand,” from Sesame Street). But it’s notquite the same with Swing. While it does have to have a beginning, middle,and end (these are, after all, basic Von Neumann architecture machines), thebig difference is that you do not have to write most of the control logic; itcomes as part of the Swing set.Look at it this way. With Swing, as with other GUI toolkits, you don’thave to write code to deal with the mouse, keyboard shortcuts, or paintingcharacters onto a graphical screen. You don’t have to write all the codeassociated with a button press, because, while it seems simple enough, a buttonpress is really a quite complex user interaction, involving repainting of thebutton’s border, possibly its shading or changing its icon, coordinating thatwith the mouse presses and releases, and deciding whether the releases happenwithin or without the boundaries of the button—all this and more, just for asimple button press. All this has been done for you, and packaged up intoSwing classes.