Currently java stable version is 8.

Oracle Java

to install it do these steps:

sudo add-apt-repository ppa:webupd8team/java
sudo apt-get update
sudo apt-get install oracle-java8-installer

if an 503 error occured, you are so bad luck because of restrictred countries:

So you must proxy your aptitude. edit /etc/apt/apt.conf file and add these lines:

Acquire::http::Proxy "your-proxy-url";
Acquire::https::Proxy "your-proxy-url";

fill with your correct proxy url. then do install steps again.

good luck!