I just applied for Amazon Technical Academy. It requires learning Java. I know Java, but not very deeply. Here are resources an Amazon cohort shared with me.
Books and Blog Posts
Practice and Challenges
- CodingBat Java — Various practice exercises
- Advent of Code — A series of puzzles for problem solving and coding
- Online practice tests for Java Certification:
Talks
- A humorous talk on silly programming language behavior
- A good talk on data structures, with examples in Java, C#, and Python (3 hours)
Dev Resources
- REPL.It — Online Java Editor/Playground
- IntelliJ Java IDE (use the community version)
- JaCoCo Code Coverage