Where can I find well-documented Java projects for beginners to read?

Question

Java

I want to read well (commented?) documented code of any open-source project.
Does anyone have a couple of links where you can see examples of good, high-quality code for self-study purposes?
If there are comments to the code, they will only be happy. It is possible with documentation as an option.

Answer 1

Go to github and search by trends and java language:
https://github.com/trending/java?since=monthly
Here are the most popular and developed turnips of the month.
Or just go look at the popular java libraries. Guava, Apache Commons, for example. Have you read the standard library yet?
Spring has well documented code.
Google also knows a lot about all sorts of examples of implementation on a particular framework, either, see, again, on the github.

Answer 2

IMHO, it's better to look at the source code in the process of using it, when it's already clear why this class / method is needed. For example, you needed ImmutableMap with Guava, in the IDE you went to the source by Ctrl + click, looked at the implementation, and now ImmutableMap does not seem like some kind of black box to you, you spied some interesting solutions. Or in spring-jdbc, JdbcTemplate, for simplified interaction with the database, and now you already know how it is implemented and there is no “magic” there, you learned the nuances of working with jdbc api, etc. The same applies to the standard library java.util.*, java.lang.* ...