Change the default Java installation used by Ubuntu

Though you have installed and using a particular Java installation (E.g. Oracle Java 7), sometimes when you install some other softwares they might change the default to other Java installations (E.g. OpenJDK)

In such situations to change the default version, run the following commands and chose the appropriate selection when prompted.

For Java :

update-alternatives --config java

For Java compiler :

update-alternatives --config javac

For Java web start :

update-alternatives --config javaws

How to instal Java in Ubuntu

This is replication of blog http://rootzwiki.com/topic/23008-howto-install-java-7-on-ubuntu-1204/

Here I give some brief note on how to Install Sun (Oracle) Java in Ubuntu and from How to set JAVA_HOME in Ubuntu post you can get to know how to set your JAVA_HOME appropriately.

For Ubuntu 12.04  for Java 7 ...
First in the terminal enter:

sudo add-apt-repository ppa:eugenesan/java
sudo apt-get update

and then install...

sudo apt-get install oracle-java7-installer 

This will give and error and stop...

Don't worry we can make this work :-)

Go to Oracle Java site [http://www.oracle.com/technetwork/java/javase/downloads/jdk-7u3-download-1501626.html] and download Java "jdk-7u3-linux-x64.tar.gz" directly from their site.

Now, move the downloaded file to /var/cache/oracle-java7-installer/

sudo mv Downloads/jdk-7u3-linux-x64.tar.gz /var/cache/oracle-java7-installer/

Then edit the oracle-java7-installer.postinst file:

sudo gedit /var/lib/dpkg/info/oracle-java7-installer.postinst

To edit scroll down and find the following:           

echo "Downloading..."
rm -f $FILENAME
WGETRC=wgetrc wget $PARTNER_URL
|| fp_exit_with_error "download failed"
rm -f wgetrc
echo "Download done."

And put a # in front of the lines between "echo "Downloading..."" and "echo "Download done."" as follows:

echo "Downloading..."
#rm -f $FILENAME 
#WGETRC=wgetrc wget $PARTNER_URL
#|| fp_exit_with_error "download failed"
#rm -f wgetrc 

echo "Download done."

Save the file and from your terminal run:

sudo apt-get install oracle-java7-installer

Now it works :-)

Check it by running:

java -version

For older versions of Ubuntu (11.10 and older)...
First in the terminal enter:

sudo add-apt-repository "deb http://archive.canonical.com/ lucid partner"
sudo apt-get update

and then install...

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

Now, Java is installed and we need to set the JAVA_HOME.
Visit How to set JAVA_HOME in Ubuntu post to get to know how you can appropriately set JAVA_HOME and PATH.

Apache MeetUp held in Hill Country

The students of University of Peradeniya did a great job organizing an amazing Apache meet up at Kandy, Sri Lanka. This was the second major event in Sri Lanka next to the Apache Bar Camp Colombo that was held this year.

Here the first talk was on "FOSS in Kandy" by Dr. Nimal Rathnayaka, followed by Dr. Srinath Perera explaining "The Apache Way" of managing projects, how the communities work together and how they resolve conflicts using the voting system with the -1 veto. 

After the introduction of open source and Apache, Nandika Jayawardrdana gave an inspiring speech on "Open source and your career" giving out some valuable informations to the audience how one can use open source to become much better at his career. Here he explained how open source can improve your communication skills, writing skills - where you have to convince and argue on your ideas via the mailing list, and how your participation on open source makes you famous - which indeed will be eye catching even at the selection phase for a grad school, and most importantly he also expressed how we get a self satisfaction when so many people are using the product that you have build. This also falls according to the famous saying "A project without users (means, it) does not exist".  

Following this, Sagara Gunathunga gave a good briefing on how you can "Find your way to Apache Contribution", Here he not only stressed on coding but also mentions some other great ways of contributing, like writing technical blogs on the project, helping with documentation and testing the project. He continued explaining how these are extremely valuable to do when you are a newbie and gain recognition from your project community. 

After lunch, we had two practical sessions, the first one is on how to configure and use Apache Web Server in an efficient manner - by Anuradha Ratnaweera, and the second was on "Apache build projects" - by Prabath Abeysekara and myself, where we demonstrated Apache Subversion, Maven and Ant. 

Finally the session was concluded with Pradeeban's lighting talk on how to build a community for your project.