The World Wide Web, for much of its existence, has been a method for distributing passive information to a widely distributed number of people. The Web has, indeed, been exceptionally good for that purpose. With the addition of forms and image maps, Web pages began to become interactive—but the interaction was often simply a new way to get at the same information. The limitations of Web distribution were all too apparent once designers began to try to stretch the boundaries of what the Web can do. Even other innovations, such as Netscape’s server push to create dynamic animations, were merely clever tricks layered on top of a framework that wasn’t
built to support much other than static documents with images and text. Enter Java and the capability for Web pages containing Java applets. Applets are small programs that create animations, multimedia presentations, real-time (video) games, multi-user networked games, and real interactivity—in fact, most anything a small program can do, Java applets can. Downloaded over the net and executed inside a Web page by a browser that supports Java, applets are an enormous step beyond standard Web design.

The disadvantage of Java is that to create Java applets right now, you need to write them in the Java language. Java is a programming language, and as such, creating Java applets is more difficult than creating a Web page or a form using HTML. Soon there will be tools and programs that will make creating Java applets easier—they may be available by the time you read this. For now, however, the only way to delve into Java is to learn the language and start playing with the raw Java code. Even when the tools come out, you may want to do more with Java than the tools can provide, and you’re back to learning the language.

That’s where Teach Yourself Java in 21 Days comes in. This book teaches you all about the Java language and how to use it to create not only applets but also applications, which are more general Java programs that don’t need to run inside a Web browser. By the time you get through with this book, you’ll know enough about Java to do just about anything, inside an applet or out.

Who Should Read This Book? Teach Yourself Java in 21 Days is intended for people with at least some basic programming background—which includes people with years of programming experience and people with only a small amount of experience. If you understand what variables, loops, and functions are, you’ll be just fine for this book. The sorts of people who might want to read this book include
you if one or more of the following is true:
■ You’re a real whiz at HTML, understand CGI programming (in perl, AppleScript, Visual Basic, or some other popular CGI language) pretty well, and want to move onto the next level in Web page design.