install sun-jdk 6, 7 on Ubuntu 12.04

http://www.devsniper.com/ubuntu-12-04-install-sun-jdk-6-7/

sudo update-alternatives --config java

sudo update-alternatives --config javac

sudo update-alternatives --install "/usr/bin/java" "java" "/usr/lib/jvm/jdk1.7.0/bin/java" 1
sudo update-alternatives --install "/usr/bin/javac" "javac" "/usr/lib/jvm/jdk1.7.0/bin/javac" 1
sudo update-alternatives --install "/usr/bin/javaws" "javaws" "/usr/lib/jvm/jdk1.7.0/bin/javaws" 1