Installing Java in Ubuntu

This is a beginner article, written from the viewpoint of a long term Windows User.

Before you install JPedal or any other Java application in Linux, make sure that java is installed on your machine. Most newer Linux distributions come with Java already installed.

To check the version of java installed, in a terminal window type:

java -version

Oracle bought Sun (the creators of Java) nearly a year ago, but the naming conventions in the current Ubuntu release still refer to Sun. In this article the terms Sun and Oracle are used interchangeably.

In Ubuntu 10.10 the default Java version is OpenJDK, an open source derivative of Java. I’m sure that OpenJDK works just fine, but JPedal was built using Oracle’s JDK (Java Development Kit), so to ensure compatibility with the other team members I needed to install the Oracle JDK.

In Ubuntu this is fairly easy – just start up the Ubuntu software center app and type ‘sun java’ in the search box. You will see an entry entitled ‘Sun Java(TM) Development Kit (JDK) 6’. Simply click on this entry and then on install and hey presto.

But not quite. The default Sun installation doesn’t install a browser plugin, so you need to do this separately. Type ‘sun java plugin’ into the Ubuntu software center app and install the entry that is listed.

Linux is setup to allow several different versions of Java to be installed on your machine at any time, but you have to manually specify which version you want to run as default – installing another version of Java doesn’t alter this. To find out what versions of java are available on your machine, open a terminal window and type:

sudo update-java-alternatives -l

To change your machine to use Oracle’s (Sun’s) Java by default, open a terminal window and type:

sudo update-java-alternatives -s java-6-sun

Next Time: Changing the default PDF viewer in Linux