Installing the Java Runtime Environment

First you need to check multiverse repository enabled or not after that open a terminal window. Since you are going to be installing the JRE and the web browser plug-in, you’ll be using the following command from a terminal

sudo apt-get install sun-java6-jre sun-java6-plugin sun-java6-fonts

Once it downloads the packages and begins the installation, you’ll get a screen that contains the Sun Operating System Distributor License for Java and hit Enter to continue. You’ll see a dialog that asks you if you agree with the DLJ license terms. Select Yes, and hit Enter; the JRE will finish installing.

Testing Java Runtime Environment

You’ll want to confirm that your system is configured properly for Sun’s JRE. This is a two-step process.

First, check that the JRE is properly installed by running the following command from a terminal.

java -version

You should get similar output

java version “1.6.0″
Java(TM) SE Runtime Environment (build 1.6.0-b105)
Java HotSpot(TM) Client VM (build 1.6.0-b105, mixed mode, sharing)
Testing Java Plugin for Firefox

open Firefox and typing about:plugins in the address bar and check for java plugin