Question on JDK, Maven and Intellij IDEA on Ubuntu. Environment variables and how to set?

Question

Java

1. Do I need to set the environment variable after installing oracle java 8 in ubuntu (installed the oracle-java8-installer, oracle-java8-set-default packages)
2. Do I need to set the environment variable after installing maven in ubuntu (installed the maven package)
3. What is the "correct" way to install intellij idea in ubuntu, I don't want to throw it at home, well, it's not an option to throw it anywhere either.