Arrays and Collections

Introduction

This lesson covers the fifth objective of the Oracle Certified Professional Java SE 21 Developer exam (1Z0-830): Working with Arrays and Collections. Oracle does not publish a weighting per objective, but collections appear in a large share of questions, directly (what does this Map operation return?) and indirectly (streams and concurrency questions use lists, maps and sets as their raw material). Java 21 adds one new topic you must know: sequenced collections (JEP 431).