Java is an object-oriented programming language developed by Sun Microsystems in the early 1990s. Java applications are compiled to bytecode, which at runtime is either interpreted or compiled to native machine code for execution.
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