Java

Java is a general purpose object oriented programming language and runtime. It is intended to let application developers “write once, run anywhere” through compiling Java code to ‘byte code’ which is then run on the Java virtual machine.

Java implementations

There are several implementations of Java available on the Linux desktop platform:

  • Oracle - v1.6, v1.7, v1.8
  • OpenJDK - v1.6, v1.7, v1.8
  • IBM - v1.7, v1.8

We strongly recommend the use of either Oracle Java 1.8 or OpenJDK Java 1.8.

You can install the different versions via Desktop Manager or if you prefer here are the commands to run in a terminal to install them instead:

Oracle Java 1.6 sudo yum install java-1.6.0-sun-devel
Oracle Java 1.7 sudo yum install java-1.7.0-oracle-devel
Oracle Java 1.8 sudo yum install java-1.8.0-oracle-devel
OpenJDK Java 1.6 sudo yum install java-1.6.0-openjdk-devel
OpenJDK Java 1.7 sudo yum install java-1.7.0-openjdk-devel
OpenJDK Java 1.8 sudo yum install java-1.8.0-openjdk-devel
IBM Java 1.7 sudo yum install java-1.7.1-ibm-devel
IBM Java 1.8 sudo yum install java-1.8.0-ibm-devel

Sadly the Java packages do not use the Environment modules system or the SCL system, so you will have to use the full path to the java or javac binaries:

Oracle Java 1.6 /usr/lib/jvm/java-1.6.0-sun.x86_64/bin/java
Oracle Java 1.7 /usr/lib/jvm/java-1.7.0-oracle/bin/java
Oracle Java 1.8 /usr/lib/jvm/java-1.8.0-oracle/bin/java
OpenJDK Java 1.6 /usr/lib/jvm/java-1.6.0-openjdk.x86_64/bin/java
OpenJDK Java 1.7 /usr/lib/jvm/java-1.7.0-openjdk/bin/java
OpenJDK Java 1.8 /usr/lib/jvm/java-1.8.0-openjdk/bin/java
IBM Java 1.7 /usr/lib/jvm/java-1.7.0-ibm/bin/java
IBM Java 1.8 /usr/lib/jvm/java-1.8.0-ibm/bin/java

Setting the default system Java

Instead of having to use the above method to use a particular version of Java you may use the alternatives command to change the default version of Java in use. This will affect every user on the system so please only do this if you are sure you will not impact other users.

Note

To set the system wide default Java you need to be in the Administrators group. See Permissions for more information.

Run the following commands and follow the instructions to change the default:

sudo alternatives --config java
sudo alternatives --config javac