Wireless Java

Preface

Most Internet technologies are designed for desktop computers or enterprise servers running on reliable networks with relatively high bandwidth. Handheld wireless devices, on the other hand, have a more constrained computing environment. They tend to have less memory, less powerful CPUs, different input devices, and smaller displays.

Since the mid-1990s, various architectures and protocols have been introduced to deal with these constraints. The Wireless Application Protocol (or WAP), which is a specification developed by the WAP Forum (http://www.wapforum.org), takes advantage of several data-handling approaches already in use. Developing wireless applications using WAP technologies is similar to developing Web pages with a markup language (e.g., HTML or XML) because WAP technologies are browser-based.

Another approach to developing wireless applications is to use the Java 2 Platform, Micro Edition (J2ME™). The Java™ programming language already plays an important role in modern programming. With WAP, you can use Java servlets and JavaServer Pages™ to generate Wireless Markup Language (WML) pages dynamically. However, with J2ME, you can now write applications in Java and store them directly on a cell phone. This adds a whole new dimension to wireless programming.

Audience

This book is about programming with J2ME on wireless devices. If you’re already familiar with the architecture, you probably noticed that the Connected Limited Device Configuration (CLDC) and the Mobile Information Device Profile (MIDP) classes are not large. Therefore, this book is correspondingly compact in size. The book acts as a quick guide for programmers who are familiar with the Java 2 Standard Edition (J2SE™) and want to get up to speed quickly with the J2ME. We assume that you are familiar with Java programming and have worked with the J2SE classes. In addition, we assume that you are familiar with setting up Java to work under various environments (Windows or Unix platforms), as well as compiling and running Java applications.

The book also serves as a quick reference for Java programmers who are interested in developing wireless software applications. The examples presented throughout the book are a good starting point for working with all the MIDP features, including user interface, networking, and databases. However, we should point out that this book is not a rehash of the entire J2SE class library. Several of the classes of java.io, java.lang, and java.net are included in the CLDC and MIDP libraries, but are less bulky than their J2SE counterparts. We assume that you already know how to use these classes, although we have included them in the API reference for completeness.