I work with Scala / Java / SQL / NoSQL / algorithms.

I code for 20+ years and worked with j2se/j2ee/powerbuilder/delphi/pascal/etc. I hold SCJP 2002 and SCWCD 2003 certificates by Sun, Scala by Coursera.

I recommend following books:

• Joshua Bloch - Effective Java
• Martin Fowler - Refactoring..
• Kent Beck - TDD by Example

and please use library Guava (ex Google Collection Framework)