Java children

File System:
   Unix is heavily based on the filesystem concept; almost everything in Unix can be treated as a file.  The kernel builds a structured file system on top of unstructured hardware, and the resulting file abstraction is heavily used throughout the whole system.

1.Arm编译器arm-linux-4.1.1，放在/usr/local下面了
2.添加编译器路径到PATH变量
export $PATH=/usr/local/arm-linux-4.1.1/bin:$PATH
可以在.bashrc文件里加，那么就不用每次都写了
3. . build/envsetup.sh 设置环境
4.chooscompo 选择配置，不同的平台我想会不一样吧。
5，make ARCH=arm CROSS_COMPILE=arm-linux- showcommands
showcommands是为了打印编译命令出来

总是跟不上变化..
第一步：安装Android环境
1. 安装 java sdk
http://java.sun.com/javase/downloads/index.jsp
  找一个最新的不带ide环境的。因为我要用eclipse
默认安装，安装后 在命令行中输入 java -version 如过这行正确就ok了
2. 安装eclipse
http://www.eclipse.org/downloads/
选 J2ee 的
3. 安装ADT
  运行eclipse
   help -->software update
   Available Softerware 选择google 的ADT后安装
4.下载Android SDK
5.设置 eclipse Android SDK目录
6.创建模拟器
7.建立一个anroid工程
 

Exception in thread "main" java.lang.NoClassDefFoundError: hello/class

java_home=E:\jdk
classpath=.;E:\jdk\lib\tools.jar;E:\jdk\lib
path=.;E:\jdk

I searched this error in google. I think my environment is right, Why?
I use "java hello.class"
Be supposed to use "java hello", not have extension.