Install java on ubuntu / switch verisons

It is so easy to install Java on Ubuntu now. On Ubuntu 7.04 (Feisty Fawn), follow these steps:

1) Make sure you have the right repositories on your sources.list file.

Edit your sources.list file the following way:

sudo gedit /etc/apt/sources.list

or if you are not using gnome (e.g. you are logged in through ssh):

sudo nano /etc/apt/sources.list

If the following lines are not already there, add them:

deb http://us.archive.ubuntu.com/ubuntu feisty main restricted
deb http://us.archive.ubuntu.com/ubuntu feisty universe multiverse

Save the file (in nano use Control-O to save and then Control-X to exit).
Now you need to tell the package manager to update it’s database:

sudo apt-get update

2) Install Java using apt-get

I currently have both Java 5 and Java 6 installed on my machine and
it’s very easy to switch between the two. Java 6 has some nice goodies such as
JSR-223 and better jconsole that I like to use.

For Java 5:

sudo apt-get install sun-java5-jre sun-java5-jdk sun-java5-plugin

For Java 6:

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

There are other packages that you might be interested in:

sun-java6-demo
sun-java6-doc
* sun-java6-source

3) Verify installation

Verify that you have the correct version of java running:

java -version

For example, on my machine (yes, I call it tiwouj):

Ubuntu Java Version

To see a list of the java versions that you have installed, you can use the following command
(it’s a letter L at the end of the command):

update-java-alternatives -l

Ubuntu Java List

This should show you a list of all the java alternatives you have installed. java-gcj is the free version of Java
from the GNU project and comes installed by default with Ubuntu so you should see it.
To switch to a different version, use the following command:

sudo update-java-alternatives -s

e.g:

sudo update-java-alternatives -s java-1.5.0-sun

Make sure it worked:

java -version

That’s it! How easy was that? You have to love apt-get.