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Introduction to Java

Java is a programming language that was originally developed at Sun Microsystems (shepherded by James Gosling and Bill Joy) in 1991. The intent of Java was to provide a platform-independent programming language and operating system for consumer electronics (TV sets, toasters and VCRs).

As it so happened however, Java did not make it into the consumer electronics market. Instead it wound up in our web browsers.

Java seemed to be a perfect fit for the Web. The language itself was extremely small (as it was built to fit inside toasters and alarm clocks with tiny amounts of memory). Thus, programs written in Java could quickly be transferred across the Web.

Further, Java was platform independent. That is, any computer with a Java virtual machine can run a Java program. Programs can be written anywhere and be run anywhere. This is crucial because if a language can not run on any machine, it cannot be used on the Web which must service every machine, language, and environment imaginable.

Platform independence works because Java is an interpreted rather than a compiled language. Unlike C or C++ code, when Java is compiled, it is not compiled into platform specific machine instructions, but into platform independent byte code. This byte code is distributed over the Web and interpreted by a Java virtual machine (typically built right into a web browser these days) on whichever platform it is being run. Perhaps a picture would be useful:

Thus, as a programmer, you need only concern yourself with the generic Java programming language and compile your applications into bytecode on whatever system you are using. You can then be assured that your bytecode will be executed correctly whether your clients are using Macs, PCs, Unix boxes or anything else.

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Selena Sol contributes to the JavaBoutique's Introduction to Java. Selena curently works for Barclays Capital in London, one of the leading global investment banks in Europe and has worked as a software developer for the National Center for Human Genome research, Microline Software, Neuron Data, and Electric Eye in Singapore. Selena is perhaps best-known for creating the Public Domain Web Script Archive (Extropia) and writing several books on Web Programming (Perl, CGI, Java).
Email: selena@extropia.com

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