我们以在Windows平台建立Java环境为例子，把问题分解成以下几步：
1 下载JDK，我们还是使用J2SDK 1.4版本，去哪里下载，呵呵，想想谁设计的Java，对Sun。
问题又来了，在http://www.sun.com/download/index.jsp?cat=Application%20Development&tab=3看到好多SDK下载，我该下什么？？
Java 2 Platform, Standard Edition (J2SE) Sun Community Source Licensing
The definitive environment for enterprise software. All available community source code versions, for Solaris/Linux/Windows.
Java 2 Platform, Standard Edition (J2SE) for Linux
A preferred platform for the development of Java applications which can then be deployed on a variety of OS platforms.
Java 2 Platform, Standard Edition (J2SE) for Windows
A preferred platform for the development of Java applications which can then be deployed on a variety of OS platforms.
Java 2 Platform, Standard Edition (J2SE) for the Solaris Operating Environment
A preferred platform for the development of Java applications which can then be deployed on a variety of OS platforms.
Java 2 Platform, Standard Edition 5.0
Java 2 SDK, Java 2 Runtime Environment (JRE), including Java Plug-in, for Solaris/Linux/Windows.
Java 2 Platform, Standard Edition v1.4
Java 2 SDK, Java 2 Runtime Environment (JRE), including Java Plug-in, for Solaris/Linux/Windows.
Java 2 SDK, Enterprise Edition, Sun Community Source Licensing
The Platform for Enterprise
注意 我们下载的是J2SE的SDK，请大家看看自己的参考书，J2ME、J2SE和J2EE有什么区别和联系。
2 下载后，在本地安装，如果你下载的是Windows平台，那么你就可以象安装其他的Windwos程序一样来进行安装
3 设置PATH 和 ClassPath环境变量 请利用原来Java课程的知识，自行设置这两个环境变量，并回忆当时老师的讲解，Path和ClassPath各有什么作用？
4 开始编写HelloWorld吧 有问题么？编译通不过？不能运行？好，你把问题反映出来吧！