Ubuntu安装sun jdk过程
从http://java.sun.com中下载jdk：jdk-6u23-linux-i586.bin，存放到/usr/java目录
1、给权限：sudo chmod u+x /usr/java/jdk-6u23-linux-i586.bin
2、安装jdk：sudo /usr/java/jdk-6u23-linux-i586.bin
3、设置环境变量：sudo gedit /etc/environment?
#set java environment
JAVA_HOME=/usr/java/jdk1.6.0_23
PATH=$PATH:$JAVA_HOME/bin
CLASSPATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar:$CLASSPATH
export JAVA_HOME PATH CLASSPATH
4、使上面设置的环境变量生效：#source /etc/environment?
5、设置ubuntu的默认jdk，原因使因为ubuntu默认有openjdk：
sudo?update-alternatives --install /usr/bin/java java /usr/java/jdk1.6.0_23/bin/java 300
sudo update-alternatives --install /usr/bin/javac javac /usr/java/jdk1.6.0_23/bin/javac 300