Java 21 Interview Questions – Practice Latest Features & Concepts
Practice Java 21 interview questions with structured explanations. Explore modern Java features like virtual threads, pattern matching, and performance improvements.
Top Java 21 Interview Questions for Freshers and Experienced Developers
Prepare for Java 21 interviews with real-world questions. Master new language features, concurrency enhancements, and modern Java practices with clear answers.
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1
What are the key features introduced in Java 21?
easyfeaturesjava21
Answer
Java 21 introduces virtual threads, record patterns, pattern matching enhancements, and sequenced collections.
Key concept: Modern concurrency and pattern matching.
Example: Virtual threads simplify scalable applications.
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2
Explain virtual threads in Java 21.
mediumvirtual-threadsconcurrency
Answer
Virtual threads are lightweight threads managed by the JVM, enabling high concurrency.
Key concept: Project Loom.
Example: Thousands of virtual threads can run efficiently.
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3
How do virtual threads differ from platform threads?
mediumthreadscomparison
Answer
Virtual threads are managed by JVM, while platform threads map to OS threads.
Key concept: Lightweight vs heavyweight.
Virtual threads scale better with lower resource usage.
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4
When should you prefer virtual threads over traditional threads?
mediumdesignperformance
Answer
Use virtual threads for IO-bound tasks with high concurrency.
Key concept: Scalability.
Avoid for CPU-heavy workloads.
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5
Explain structured concurrency in Java 21.
hardconcurrencyarchitecture
Answer
Structured concurrency treats multiple threads as a single unit.
Key concept: Task grouping.
Improves error handling and cancellation.
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6
What problem does structured concurrency solve?
hardconcurrencydesign
Answer
It simplifies managing multiple threads and avoids thread leaks.
Key concept: Lifecycle control.
Example: Cancel all child tasks on failure.
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7
What are record patterns?
mediumpatternsrecords
Answer
Record patterns allow destructuring of record objects.
Key concept: Pattern matching.
Example: Extract fields directly in switch.
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8
Explain pattern matching for switch in Java 21.
mediumswitchpatterns
Answer
Enhances switch to support type patterns and guards.
Key concept: Type-safe branching.
Example: case String s -> s.length();
