I prepared Android app codes with Google Maps and clustering feature. Feel free to use these as basis for your new projects.
They are on GitHub:
 Default Map Markers:
 Custom Map Markers:
I simply took the necessary classes and res files from Android Maps Utility demo, and then placed them into bare Android Studio projects for simplicity. For me, it’s easier to start a new “maps with clustering” project on simple apps like these, rather than downloading the entire Android Maps Utility Demo, picking out the necessary files, and fixing errors before getting started each time. 😆