I need to take an online Java assessment as part of an interview process for a job I'm looking into. The job is mainly in Java. While I started programming Java 4(5) years ago, I never got into super complicated stuff. I've done DB, Swing, AWT, JDBC, and other assorted things so I have some experience. I've programmed several apps in Android Studio as well.

Question is, I have 6 days left to take the assessment. What are the absolutely essential things to understand about Java? I know classes, extends, implements, public private extern static and the basics. I know about listeners and events. What else should I know before taking this assessment?

If any of you could help me brush up on my Java skills for this interview, I would greatly appreciate it.

Edgar

Just saying good luck, I've only dabbled with Java.

Well, I suppose it kind of depends what are you going to be coding.
But nowdays I believe multi-threading is getting more & more important, & java offers easy stuff for this. But well, you better do know what it does & how to use it.

Mostly it's about runnable & synchronized I guess, I assume you know what statics are.

Multithreading (mutex, semaphores, locks, synchronize keyword, join, etc)
Multithreading pitfalls (deadlock, etc) (producer consumer)
Why shouldn't you stop() a thread?
Difference between process and thread
Virtual memory
Garbage Collection
Packages
Other design patterns (Factory)
SOLID Principals
Are methods virtual by default in Java?
Pass by value, by reference, why?
Why can't I make a generic of int, why must I box it into Integer?
Lambdas, anonymous functions, etc
Closures
Oerator overloading / lack thereof (String?)
the final keyword, why/when to use
Unit/Component/Integration testing (mocks, test doubles, etc)
Can I allocate something on the stack (like a value type in C#)?
If I do not prefix my member variable with public, private, etc, what is the default scope?
Does Java support multiple inheritance? Why not?
Reflection
Java byte code (JVM)
Shallow/deep copy

Thank you jmasterx, that's very helpful. I'll be studying over the weekend.

Elias, Bruce Perry, do you have anything to add? You guys develop in Java professionally, right?

Good luck - hope it goes well.

Thanks jmasterx, but I didn't get the job. There are just too many applicants, and no one seems to care that I've been programming 12 years and have a degree. And that was an entry level job! Google didn't want me last year, I suppose I could reapply but California is too far. I didn't end up taking the test, so I guess I have more time to prepare now. And I'm getting back into the swing of things with my Java code.

Yes, I'm aware of Swing. No pun intended though....

EDIT
And oh do I hate Swing. My least favorite gui of all times.