Learn how to compile Android source code

If you want to study the core detail of Android, you can browse and explore the source code here. 

https://android.googlesource.com/

You can clone one of these repositories, you need to install git, and run:

git clone https://android.googlesource.com/name

You can get the complete Android platform on your computer and modify and build it to suit your needs and contribute to the Android communities.

If you are device developer, you can port the android to your device.