As we all know with the Android law-suits with Oracle vs Google on the whole Java issue, some clever people thought that instead, just port all of the Android code automatically to C#. And, they’re getting there!
Basically, they take the Android AOSP code then pull it through a tool they have helped develop called “Sharpen” which translates Java code to C# and the results are amazing. While only some of the Android code is physically working without Java at all, it’s a great start and hopefully seeing this on low-end devices can speed things up a little.
A little more on the technical side, the way Android runs Java through the Dalvik virtual machine is fairly efficient, but using Java limits you severely by it’s design and complexity, slowing down execution everywhere. While Android appears to do a fairly good job, it doesn’t do it as well as it could do with Oracle’s efforts (if it wanted to put them in).
To make this clearer, here’s a graph from the people behind the project showing performance:
As you can see, clearly using the C# (Mono as it’s displayed on the graph) is faster. However, there’s still a while to go which if you want to have a look or even help out check out the link in the source. There’s a lot more technical information over there too!