Ubuntu 12.04 - Install Oracle Java JDK 7

go to http://www.oracle.com/technetwork/java/javase/downloads/index.html and download or use command below:
    wget http://download.oracle.com/otn-pub/java/jdk/7u7-b10/jdk-7u7-linux-i586.tar.gz

extract the package:
    tar -xvf ~/Downloads/jdk-7u7-linux-i586.tar.gz

create a folder for Java JDK files and folders by running the commands below:
    sudo mkdir -p /usr/lib/jvm/jdk1.7.0

move all the JDK files and folders to the new location by running the commands below:
    sudo mv jdk1.7.0_07/* /usr/lib/jvm/jdk1.7.0/

copy and paste each command as shown below one-at-a-time to enable Java JDK:
    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

create a Mozilla plugins folder in your home directory:
    mkdir ~/.mozilla/plugins/

create a symbolic link to your Mozilla plugins folder. For 64-bit systems, replace ‘i386’ with ‘amd64’:
    ln -s /usr/lib/jvm/jdk1.7.0/jre/lib/i386/libnpjp2.so ~/.mozilla/plugins/