installs JDK 7

sudo apt-get install python-software-properties
sudo add-apt-repository ppa:webupd8team/java
sudo apt-get update
sudo apt-get install oracle-java7-installer


# or if you want JDK 8:
# sudo apt-get install oracle-java8-installer
# these commands install Oracle JDK7/8 and set them as default VMs automatically:
# sudo apt-get install oracle-java7-set-default
# sudo apt-get install oracle-java8-set-default