What do the Rolling Stones and Sun(tm) Microsystems have in common? First, both organizations have sites on the World Wide Web to promote their work. Second, each has chosen Java as a new way to enliven their World Wide Web pages.

WHAT IS JAVA ?

Java is a programming language developed by Sun Microsystems that brings animation and interaction to the World Wide Web. HotJava is the name of the software developed by Sun which you can use to observe and interact with Java programs. Java unleashes a level of interactivity that has never been possible on the Web. This book explores and introduces you to Java 's potential for distributing interactive, executable content.

People and organizations use the World Wide Web to communicate globally and instantly. Using the Internet as a network for data transfer, the Web employs a form of expression called hypertext that connects related information in web-like structures. Combined with multimedia, the resulting webs of hypermedia have opened new possibilities for expression and communication.

But something has been missing from the Web since its introduction to the world in the early 1990s. Although the amount of Web data traffic and the number of computers offering information on the Web has risen dramatically, the content of the pages has lacked important expressive and interactive qualities. While often intriguing, informative, and useful, Web content has been devoid of the degree of interactivity offered by many multimedia and hypermedia systems that run on non-networked computers. So although the Web fostered world-wide interconnections among people and information, it has only enabled people to observe: read text, watch videos, listen to music, and explore information.

The unbounded universe of possibilities on the Web may lead some users to feel that the hyperlinks just keep leading them on, until ultimately, the Web seems just a road to nowhere: with no there there. Java changes all this. Java makes destinations possible for Web users.

Java enables developers to create content that can be delivered to and run by users on their computers. This software can support anything that programmers can dream up: spreadsheets, tutorials, animations, and interactive games. With the Web page as the delivery platform, this software can support a variety of information tasks with true interactivity; users can get continuous, instantaneous feedback for applications in visualization, animation and computation. Users of the Web in the dawning Java age may indeed find a there on the Web: a place to play, work, or learn.

Why Java ?

Java is just one part of the integrated set of systems that support World Wide Web communication. Java is an entirely separate programming language from the markup scheme for defining hypertext, the Hypertext Markup Language (HTML). Java doesn't replace HTML, nor does it negate all current work that has been developed or deployed on the Web.

Java connects with HTML and the Web through a special HTML tag called APPLET, which allows developers to include special Java programs called applets on Web pages. These applets are essentially software programs that the user's browser downloads (automatically, as part of Web page observation) and executes. With graphical input and output possible through the applet on the page, Java thus opens windows to into richer levels of interactivity on the Web.

Why This Book?

The purpose this book is to give you an understanding of what Java is, how it transforms Web communication, and Java 's principle technical features.

This book delves into the possibilities Java offers in animation, interaction, and distributed network communication. This book aims to help you

How to Use This Book

This book is an introduction to Java 's essentials: how Java connects with the Web, how to view Java programs, and the basics of constructing Java programs. This book is organized so that users at all levels can traverse it in a variety of paths.

The Scope of This Book

This book discusses the significance of Java and showcases the kinds of applications it makes possible. This book provides a quick overview of the HotJava browser, how to obtain it, and how it can be used to navigate the Web. The book then surveys the main features of the Java language, describing the basics of its procedural programming features and how it supports the object-oriented paradigm. This language description includes many examples[md]showing the very basics for applets and applications. Finally, the book surveys many existing Java programs and examines what kind of communication they make possible and the basics of how they work.

This book cannot possibly do justice to the rich and very rapid ways that Java is developing technically and expressively. As such, this book is limited in two ways:

  1. It covers the alpha release of Java /HotJava that was available in the summer of 1995. A beta release of Java /HotJava is expected for later in 1995. The support web for this book (http://www.december.com/works/java.html) contains a summary of changes relevant to this book after the beta release is available.
  2. This book is not meant to be a comprehensive reference or advanced programming guide for Java . It instead provides a quick start for new users, project planners, and developers, with coverage of introductory conceptual and beginning technical information about Java , with pointers to online locations of full and current reference information.

Organization of This Book

This book is organized into parts, each of which contains three chapters. Each part introduces the essentials of Java from a different perspective, and each chapter in the parts addresses a central main point stated in a declarative sentence as the chapter title. Here is a summary of the contents in these parts:

Who Might Use This Book?

How Might You Use This Book?

Online Support

To connect to the latest information about this book's contents, open the URL:

http://www.december.com/works/java.html

This support web provides links to online information about the book, code samples discussed, and updates on resources and related information. Check with the errata page of this support web for corrections, and send reports of other errors, questions, or comments to the author at john@december.com.

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