jdk - installing jdk8 in ubuntu 12.04

I am completely new to Ubuntu and I want to install jdk8. I downloaded the jdk-8u25linux-x64.tar.gz file from their website, but I wanted to follow a lot youtube videos but somehow I cannot follow them. lastly I tried with

https://stackoverflow.com/questions/25729592/how-to-install-jdk-8-in-ubuntu-12-04-using-tar-gz-file

but when I entered sudo add-apt-repository ppa:webupd8team/java and asks for my password, I give the password and press enter and it is blank, nothing happens afterwards.

please write some step by step solution and solve my problem