software installation - How can I install Sun/Oracle's proprietary Java JDK 6/7/8 or JRE?

I want to install Oracle's JRE and to update to the latest version with the Software Updater when they released. Is there a Ubuntu package that is provided by Canonical or Oracle?

Before release Java 7, I followed this way to install Java 6.

But it doesn't work for Java 7. There is no package sun-java7-xxx. How can you install Java 7?