From 21 Sep 2017 on we have OpenJDK 9 in the backports repository for Debain Stretch. Perform the following steps to install version 9.
Installing OpenJDK 8 on Debian Jessie
Be aware that this tutorial was written for Debian Jessie. If you are using Debian Stretch (or Ubuntu Xenial Xeres / Bionic Beaver) you can just install OpenJDK version 8 right away or learn how to install OpenJDK 9
Since OpenJDK 8 is out there since march 2014 I wanted to install it on my freshly setup Debian Jessie. But trying to, I was surprised that the OpenJDK is only available in version 7. To successfully install version 8 you need to perform the following steps.