When Sun Microsystems was still the head of Java, the wise decision to OpenSource it was made. (Thank you, whoever was behind it…) OpenJDK as of today can be built without any binary plugs, so it can be considered as really OpenSource and free. To exercise the liberty of building your own, runnable Java it takes amazingly low effort – that is the topic if this short blog entry.
While consumers and corporate IT seems to prefer Windows as primary operating system, developers tend to choose a unixoid OS: Linux (Debian, Arch, Ubuntu), Apple OSX or OpenSolaris. OpenSolaris lacks a current open source desktop distribution Ubuntu was chosen for this example. To add some complexity Canonical went with a multi-arch setup since Ubuntu 11.04 which looks like being extended/change on Ubuntu 12.04. (This is described on the MultiArch wiki page. We will come back to the problems caused by the transition later in the article.)
In order to retrieve the OpenJDK sources mercurial has to be installed: