Refactoring-Summary VS dagger

I find that reading books rather than code tends to be more helpful in terms of finding good takes on what clean code is -- more specifically books on refactoring or specific language-related features (like 'Effective Java' or 'Fluent Python'). The issue with just reading code is that many times - you'll miss out on why the author chose to use the expression or abstractions which they chose to use. Reading a book at least takes you through author's thought process. For an alternative - you could always browse repositories which contain notes on refactoring as well like this one (which does a good job summarizing some of the key principles from Fowler's book on refactoring):

https://github.com/HugoMatilla/Refactoring-Summary

https://github.com/HugoMatilla/Refactoring-Summary#28-encapsulate-collection

I learned a ton about Java and pragmatic algorithm development from reading Dagger (https://github.com/square/dagger) and porting it to C#. It's small enough that you can grok it in a reasonable amount of time, but sophisticated enough that there's a lot to learn. (Yes it's deprecated in favor of Dagger 2, but the latter is a tougher slog IMO)

Actually most of the big Square OSS libraries are great to read - okio, okhttp, picasso.