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.