Installing the Java Runtime Environment
Once you've got the multiverse repository enabled, installing Sun's Java package, file extension jad is easy. Simply open a terminal window and apt-get the package. 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 window:
:~$ sudo apt-get install sun-java5-jre sun-java5-plugin \\
sun-java5-fonts
Once apt-get downloads including file extension jad the packages and begins the installation, you'll get a screen that contains the Sun Operating System Distributor License for Java. Read the license, if you wish, 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.
At this point, Java is installed.
Confirming the Installation
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:
:~$ java -version
java version "1.5.0_06"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_06-b05)
Java HotSpot(TM) Client VM (build 1.5.0_06-b05, mixed mode, sharing)
If you see an unexpected version of Javain particular, one identified as "gij (GNU libgcj)"then you probably have GNU Java installed. You can easily switch from one Java to another with the command sudo update-alternatives --config java, which will prompt you to choose which Java implementation to use. Pick the one in /usr/lib/jvm to use the JRE you just installed.
If the JRE is properly installed, confirm that the Java plug-in is installed in your browser by opening Firefox and typing about:plugins in the address bar
Congratulations, you've caffeinated your browser! You can now surf to Java-enabled web sites and use Java applications!
About JAD File
When us download application or game to hp java, sometime we can choose file extension jad or jar be like application java application on file extension jad
Possibly you still confuse what is difference between file extension JAD and JAR, So here I try to embrace from various source to explain a little a few 2 the mentioned.
file extension JAD is abbreviation from Java Application Descriptor. From just him name we can know that file extension JAD is the file description concerning application Java ( MIDLET). Application Java which? Of course the application in file JAR, because file extension JAD frankly only a ordinary text file, which one file extension JAD seen contents its alike once with MANIFEST the in file JAR.

