Check if java JDK is installed correctly
dpkg --list | grep -i jdk
if not install JDK
sudo add-apt-repository ppa:webupd8team/java
sudo apt-get update && sudo apt-get install oracle-jdk7-installer
After the installation you have enable the jdk
update-alternatives --display java
Check if Ubuntu uses Java JDK 7
java -version
If all went right the answer should be something like this:
java version “1.7.0_25″
Java(TM) SE Runtime Environment (build 1.7.0_25-b15)
Java HotSpot(TM) Server VM (build 23.3-b01, mixed mode)
Check what compiler is used
javac -version
It should show something like this
javac 1.7.0_25
Add JAVA_HOME to environment variable
Edit /etc/environment and add JAVA_HOME=/usr/lib/jvm/java-7-oracle to the end of the file
sudo nano /etc/environment
Append to the end of the file
JAVA_HOME=/usr/lib/jvm/java-7-oracle
Log in and out (or reboot) for the changes to take effect.
If you want to remove oracle JDK
sudo apt-get remove oracle-jdk7-installer