Interesting open source APIs (Java) for self-education?

Question

What are your top 3 open source APIs (in Java) that you recommend as an example of a well-designed work of art? This will be the code that you enjoy viewing and getting some ideas from. Any valid valid region.

The emphasis here is on the quality of training / code research, the level of complexity - from intermediate to upper level .

Thanks so much for the answers.

Answer 1

I think google collections is a great place to start. Josh Bloch advised developing it a lot, and the API did it very well. While Spring is great, a little understanding of where to start. A good introduction to google collections is "coding in small with Google collections" (I cannot post the actual link due to the spam filter on the stack).

Answer 2

1.Spring 2.Hibernate

Answer 3

• Spring is a very well written and designed framework. It's a hell of a lot of software, but if you want an example of building a modular scheme, you can't go wrong looking at the spring code base.

Answer 4

Sources of java libraries are well documented.

In my experience, the most valuable work includes documentation on desgin solutions, if you see a good API, it will be very interesting what alternatives there can be. Unfortunately, these are mostly overloaded project mailing lists.

Answer 5

Not an external library, but the java.util.concurrent package is very beautifully written. The code is not simple, but it is very well thought out and, in my opinion, it is written brilliantly.