Java is a programming language and computing platform first released by Sun Microsystems in 1995. It is the underlying technology that powers state-of-the-art programs including utilities, games, and business applications. Java runs on more than 850 million personal computers worldwide, and on billions of devices worldwide, including mobile and TV devices.
There are lots of applications and websites that won't work unless you have Java installed, and more are created every day. Java is fast, secure, and reliable. From laptops to datacenters, game consoles to scientific supercomputers, cell phones to the Internet, Java is everywhere!
Install Oracle java 7 in debian
Login as root and run the following commands from your terminal
echo "deb http://ppa.launchpad.net/webupd8team/java/ubuntu precise main" > /etc/apt/sources.list.d/webupd8team-java.list
echo "deb-src http://ppa.launchpad.net/webupd8team/java/ubuntu precise main" >> /etc/apt/sources.list.d/webupd8team-java.list
apt-key adv --keyserver keyserver.ubuntu.com --recv-keys EEA14886
apt-get install oracle-java7-installer