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編譯器arm-linux-4.1.1，放在/usr/local下面了
2.添加編譯器路徑到PATH變量
export $PATH=/usr/local/arm-linux-4.1.1/bin:$PATH
可以在.bashrc文件里加，那么就不用每次都寫了
3. . build/envsetup.sh 設置環境
4.chooscompo 選擇配置，不同的平臺我想會不一樣吧。
5，make ARCH=arm CROSS_COMPILE=arm-linux- showcommands
showcommands是為了打印編譯命令出來

總是跟不上變化..
第一步：安裝Android環境
1. 安裝 java sdk
http://java.sun.com/javase/downloads/index.jsp
  找一個最新的不帶ide環境的。因為我要用eclipse
默認安裝，安裝后 在命令行中輸入 java -version 如過這行正確就ok了
2. 安裝eclipse
http://www.eclipse.org/downloads/
選 J2ee 的
3. 安裝ADT
  運行eclipse
   help -->software update
   Available Softerware 選擇google 的ADT后安裝
4.下載Android SDK
5.設置 eclipse Android SDK目錄
6.創建模擬器
7.建立一個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.