JRE refers to the Java Runtime Environment. To run any java programm you need to have JRE installed in your computer. Java is platform independent meaning it can run in any platform whether its Linux, Windows or Mac However the particular computer must have JRE installed in their system. to install JRE in Ubuntu 11.10 just follow the below instruction.
Open the terminal and Run the following command
sudo apt-get install openjdk-7-jre
To Run java in your web browser
sudo apt-get install icedtea6-plugin
If you are java programmer click here to install netbeans with TOMcat and glassfish server in any Linux distribution.