Quiz

# Java quiz

1) Records are:
   a) mutable POJOs
   b) compact immutable data carriers with auto-generated equals/hashCode/toString
   c) interfaces with default methods
   d) abstract classes

2) Sealed types let you:
   a) lock the file from edits
   b) restrict which classes can implement an interface or extend a class
   c) prevent reflection
   d) enable bytecode signing

3) Virtual threads (Java 21):
   a) are OS threads
   b) are lightweight scheduled by the JVM, cheap to create by the million
   c) replace ForkJoinPool
   d) only work on Linux

4) Optional.get() should be used:
   a) freely
   b) only after isPresent() or with orElse / orElseThrow
   c) never
   d) inside finally

5) Streams are:
   a) IO streams
   b) lazy pipelines that compute on terminal operations
   c) eager arrays
   d) always parallel

6) Pattern matching for switch on Java 21 supports:
   a) types only
   b) types, deconstruction, and guards
   c) regex
   d) primitives only

7) try-with-resources requires the resource to implement:
   a) AutoCloseable
   b) Iterable
   c) Comparable
   d) nothing

8) The Java module system (JPMS) helps you:
   a) install dependencies
   b) declare strong encapsulation and dependencies at module level
   c) replace Maven
   d) compile to native by default

Answers: 1b, 2b, 3b, 4b, 5b, 6b, 7a, 8b.

// 3 questions per lesson.