Currently Ubuntu has the following Java packages
sun-java6-bin -- Contains the binaries
sun-java6-demo -- Contains demos and examples
sun-java6-doc -- Contains the documentation
sun-java6-fonts -- Contains the Lucida TrueType fonts from the JRE
sun-java6-jdk -- Contains the metapackage for the JDK
sun-java6-jre -- Contains the metapackage for the JRE
sun-java6-plugin -- Contains the plug-in for Mozilla-based browsers
sun-java6-source -- Contains source files for the JDK
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.
You should get similar output
Testing Java Plugin for Firefox
open Firefox and typing about:plugins in the address bar and check for java plugin