Needed to do a project in Java8, here’s how to install openjdk8:
sudo add-apt-repository ppa:openjdk-r/ppa
sudo apt-get update
sudo apt-get install openjdk-8-jdk
sudo update-alternatives --config java # select openjdk8
sudo update-alternatives --config javac # select openjdk8
sudo apt-get purge maven maven2 maven3
sudo add-apt-repository ppa:andrei-pozolotin/maven3
sudo apt-get update
sudo apt-get install maven3
If want Oracle Java 8 JDK:
sudo add-apt-repository ppa:webupd8team/java
sudo apt-get update
sudo apt-get install oracle-java8-installer
sudo vi /etc/environment
# add JAVA_HOME="/usr/lib/jvm/java-8-oracle"