What is a project for learning Java frameworks?

Question

Java

I'm going to improve my Java level over the summer so that after that I can try to get an internship.
I tried to find out what is most in demand now, and made an approximate list for myself:
1) Spring
2) Hibernate
3) SQL (not a framework, but also important)
4) Perhaps Play - I didn’t find much information on it.
I think the best way to learn this is while working on your own project that uses these technologies. Can you suggest an idea for such a project?
The current level in Java is "I can write a game in LibGDX".