Assess HashMap vs ConcurrentHashMap
Overview
This question evaluates a candidate's understanding of Java concurrency, thread-safety of collection implementations, and performance trade-offs in hash-based maps, testing skills in multi-threading, data structures, and concurrent programming within the Coding & Algorithms domain.
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Aug 7, 2025, 12:00 AM
Software Engineer
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Coding & Algorithms
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Is Java's HashMap thread-safe? Explain why or why not. How does ConcurrentHashMap achieve thread safety and performance (e.g., lock striping, CAS operations, non-blocking reads, tree bins under high collisions, resizing strategy) in modern JDKs? Discuss typical pitfalls and when to prefer each.