Ubuntu jdk

  sudo update-alternatives --install /usr/bin/javac javac /usr/lib/jvm/jdk1.6.0_45/bin/javac 1


   sudo  update-alternatives --install /usr/bin/java java /usr/lib/jvm/jdk1.6.0_45/bin/java 1


   sudo  update-alternatives --install /usr/bin/javaws javaws /usr/lib/jvm/jdk1.6.0_45/bin/javaws 1


    sudo update-alternatives --install /usr/bin/jar jar /usr/lib/jvm/jdk1.6.0_45/bin/jar 1


    sudo update-alternatives --config javac


    sudo update-alternatives --config java


    sudo update-alternatives --config javaws


sudo     update-alternatives --config jar