Chapter 1: Java, what is it? - Java Language Tutorial

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Java is an object oriented language in which different components such as applications, applets, servlets etc. are written.
When a Java program is compiled, it is turned into byte codes that are the portable machine language of a CPU architecture known as the Java Virtual Machine (or shortly the JVM).
This is a major difference to other native languages such as C and C++ as programs written in those languages is compiled into machine codes immediately. This reduces the portability since a program has to med compiled for that specific platform.
The byte codes that Java is compiled into can be run on any virtual machine on any platform. It is the virtual machine that has to be created for a specific platform, not the ordinary Java-programmers code.

There are three major parts one should know about when talking about Java:

The virtual machine

The Java Virtual Machine is as mentioned an interpreter of byte codes that has been generated from source code.
As mentioned Java programs are portable to many platforms, that is, as many platform as the JVM has been ported (which is most of them including Unix, Linux, Windows, Windows CE and Palm OS to name a few).

The Java Platform

The Java platform consists of a wide range of classes to be used by every programmer.
Since it is portable, no adjustments need to be made when running the same program on different platforms (as opposed to writing a C program on Windows, using the Win32 API and then do the same on a Linux computer).
The platform can be divided into the 'Standard Edition' which is commonly used for client programming, and the 'Enterprise Edition' which is used a lot for server programming.

The Java Programming Language

The language itself is of course the most central part and as mentioned it is an object oriented language which is fairly simple to learn and easy to use.
This tutorial will show just how simple and easy to learn it is, so read on!'

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