My primary goal in writing this book was to explain the Java virtual machine, and several core Java APIs closely related to the virtual machine, to Java programmers. Although the Java virtual machine incorporates technologies that had been tried and proven in other programming languages, prior to Java many of these technologies had not yet entered into common use. As a consequence, many programmers will be encountering these technologies for the first time as they begin to program in Java. Garbage collection, multi-threading, exception handling, dynamic extension--even the use of a virtual machine itself--may be new to many programmers. The aim of this book is to help programmers understand how all these things work, and in the process, to help them become more adept at Java programming.

Another goal I had in mind as I wrote this book was to experiment a bit with the changing nature of text. Web pages have three interesting characteristics that differentiate them from paper-based text: they're dynamic (they can evolve over time), they're interactive (especially if you embed Java applets in them), and they're interconnected (you can easily navigate from one to another). Besides the traditional text and figures, this book includes several Java applets (in a mini-web site on the CD-ROM) that serve as "interactive illustrations" of the concepts presented in the text. In addition, I maintain a web site at artima.com on the internet that serves as a launching point for readers to find more (and more current) information on the topics covered in the book. This book is composed of all of these components: text, figures, interactive illustrations, and constantly evolving links to further reading.