Check if your 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-java8-installer
After the installation you have to enable the jdk
update-alternatives --display java
Check if Ubuntu uses Java JDK 8
java -version
If all went right the answer should be something like this:
java version "1.8.0_91"
Java(TM) SE Runtime Environment (build 1.8.0_91-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.91-b14, mixed mode)
Check what compiler is used
javac -version
It should show something like this
javac 1.8.0_91
Finally, add JAVA_HOME to the environment variable
Edit /etc/environment and add JAVA_HOME=/usr/lib/jvm/java-8-oracle to the end of the file
sudo nano /etc/environment
Append to the end of the file
JAVA_HOME=/usr/lib/jvm/java-8-oracle
You will then have to reboot, you can do this from the terminal with:
sudo reboot
In case you want to remove the JDK
sudo apt-get remove oracle-java8-installer