181. What is the purpose of the 'jwebserver' tool (Java 18+)?
- a) To deploy web applications
- b) To provide a simple HTTP server
- c) To analyze web traffic
- d) To optimize web services
Answer: B - Minimal HTTP server for prototyping and testing.
182. Which is not a valid Java virtual thread feature (Java 19+)?
- a) Lightweight threads
- b) Managed by JVM
- c) Mapped 1:1 to OS threads
- d) High throughput
Answer: C - Virtual threads use M:N mapping to OS threads.
183. What is the purpose of the 'Vector API' incubator feature?
- a) To handle mathematical vectors
- b) To express vector computations
- c) To replace java.util.Vector
- d) To implement geometric algorithms
Answer: B - For expressing vector math computations that compile to optimal hardware instructions.
184. Which is not a valid Java pattern matching use case?
- a) instanceof checks
- b) switch expressions
- c) try-catch blocks
- d) record deconstruction
Answer: C - Pattern matching isn't used with try-catch (as of Java 19).
185. What is the purpose of the 'Foreign Function & Memory API'?
- a) To call native code
- b) To manage off-heap memory
- c) To interoperate with C libraries
- d) All of the above
Answer: D - Enables Java programs to interoperate with native code and memory.
186. Which is not a valid Java 19 language feature?
- a) Record patterns
- b) Virtual threads
- c) Pattern matching for switch
- d) Value types
Answer: D - Value types are not yet part of standard Java (as of 19).
187. What is the purpose of the 'Structured Concurrency API' incubator?
- a) To manage thread pools
- b) To treat multiple tasks as single unit
- c) To implement async/await
- d) To replace ExecutorService
Answer: B - Treats related async tasks as single unit of work.
188. Which is not a valid Java 20 preview feature?
- a) Record patterns
- b) Pattern matching for switch
- c) Virtual threads
- d) Foreign function API
Answer: C - Virtual threads were finalized in Java 21 (preview in 19).
189. What is the purpose of the 'Scoped Values' incubator feature?
- a) To replace ThreadLocal
- b) To provide immutable method parameters
- c) To implement value scoping
- d) To optimize memory usage
Answer: A - Designed to be a better alternative to ThreadLocal for virtual threads.
190. Which is not a valid Java 21 feature?
- a) Virtual threads
- b) Record patterns
- c) String templates
- d) Value types
Answer: D - Value types are not yet part of standard Java (as of 21).
191. What is the purpose of the 'String Templates' preview feature?
- a) To simplify string formatting
- b) To enable template engines
- c) To optimize string concatenation
- d) To implement heredoc strings
Answer: A - Simplifies string interpolation with embedded expressions.
192. Which is not a valid Java concurrency improvement in recent versions?
- a) Virtual threads
- b) Structured concurrency
- c) Scoped values
- d) Parallel streams
Answer: D - Parallel streams existed since Java 8 (not a recent improvement).
193. What is the purpose of the 'Unnamed Patterns and Variables' preview?
- a) To skip unused pattern variables
- b) To implement wildcards
- c) To optimize pattern matching
- d) To replace null checks
Answer: A - Allows using underscore _ for unused pattern variables.
194. Which is not a valid Java 22 preview feature?
- a) String templates
- b) Implicit classes
- c) Unnamed variables
- d) Foreign function API
Answer: B - Implicit classes are not a current Java feature.
195. What is the purpose of the 'Region Pinning for G1' feature?
- a) To optimize GC for virtual threads
- b) To reduce GC pause times
- c) To implement memory regions
- d) To replace ZGC
Answer: B - Reduces GC pauses by avoiding unnecessary region evacuations.
196. Which is not a valid Java future feature under consideration?
- a) Value types
- b) Universal generics
- c) Extended enums
- d) Operator overloading
Answer: D - Operator overloading is not currently being considered.
197. What is the purpose of the 'Leyden' project?
- a) To optimize startup time
- b) To create static images
- c) To reduce memory footprint
- d) All of the above
Answer: D - Aims to improve Java startup, performance, and footprint.
198. Which is not a valid Java enhancement proposal (JEP) in recent versions?
- a) JEP 425: Virtual Threads
- b) JEP 428: Structured Concurrency
- c) JEP 420: Pattern Matching
- d) JEP 450: Value Types
Answer: D - There is no JEP 450 for Value Types (as of Java 21).
199. What is the purpose of the 'Amber' project?
- a) To improve Java syntax
- b) To optimize performance
- c) To enhance security
- d) To implement new GC algorithms
Answer: A - Focuses on productivity-oriented language features.
200. Which is not a valid Java project (OpenJDK initiative)?
- a) Loom
- b) Valhalla
- c) Panama
- d) Sparta
Answer: D - There is no Sparta project (but there is Skara for source control).