I would like to upgrade my main system to 16.04, but I work on projects that require OpenJDK 7. Apparently it is not available from a trivial apt-get install openjdk-7-jdk. Only versions 8 and 9 are listed in the repository. Can anyone point me to instructions on how to install it?
![How do I install openjdk 7 on Ubuntu 16.04 or higher?](https://cdn-ak-scissors.b.st-hatena.com/image/square/664a2d3dc991972667a15e0e849615b9670c436b/height=288;version=1;width=512/https%3A%2F%2Fcdn.sstatic.net%2FSites%2Faskubuntu%2FImg%2Fapple-touch-icon%402.png%3Fv%3Dc492c9229955)