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The Java programming language was created by Sun Microsystems to facilitate the development of both client-based and server-based applications. The Java language can really be viewed as a whole platform, since it specifies not only a programming language and the associated syntax and APIs, but also a runtime environment known as a virtual machine. The Java Virtual Machine (JVM) specification describes a sort of generic computer-the Java Virtual Machine-that is essentially emulated on top of actual hardware. Sun's Java 2 Software Development Kit (J2SDK) consists of both a set of tools (such as a compiler) for the Java language and a JVM for running applications. Countless books have been written on the equally countless aspects of the Java platform, and so this book doesn't go there. Interested readers can look into any of the books on the market (such as Java in a Nutshell by David Flanagan, and Learn Java with JBuilder 6 by John Zukowski).
The Java 2 Software Development Kit-J2SDK-is a product of Sun Microsystems. However, other vendors (such as IBM) that produce similar software for running and developing Java software frequently call their products a Java Development Kit (JDK). Moreover, Sun itself also formerly called its J2SDK a JDK.
You can think of the term "JDK" as describing the class of software that is used for developing and running Java software, whereas "J2SDK" is simply the name of Sun's particular version of a JDK. This is the terminology used in this chapter.
The J2SDK is a proprietary product. That is, even though Sun makes the specifications for the Java programming language and Java Virtual Machine freely available, the actual product of the J2SDK is Sun's proprietary software. Source code for the J2SDK is available; however, don't confuse this with open source software, since the Sun Community Source License under which Sun provides the code is not an open source license! For many of you, of course, this doesn't matter, and this book itself takes a pragmatic approach: sometimes, proprietary software is simply a necessity. A great many professional developers need to use Sun's J2SDK on Linux systems, so this chapter is provided to show you how. The upshot for you, however, is that in order to install this software, you must agree to a proprietary (but no-cost) software license. Examine this license carefully before agreeing to it and performing any of the steps in this chapter.
See Chapter 2 for more information about open source software.
Java is a full-blown programming language, and so it may not by itself be of interest to readers who aren't software engineers or programmers. However, the inclusion of the J2SDK as an example is primarily to demonstrate the installation of a proprietary software package that requires extensive user environment customizations to function properly. It's a great illustration of some very useful techniques, so even nondevelopers may wish to read this section.
Purpose: Provides a runtime environment and development tools for the Java programming language.
Authors: Sun Microsystems, the Blackdown Project
Web sites: http://www.java.sun.com/j2se and http://www.blackdown.org
Description: The Java programming language is Sun's highly portable platform for developing many types of applications, including GUI client programs, enterprise server applications, and small web-based applets.
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