Java Questions on Collections

Short summary

Deep walkthrough of HashMap internals: array-backed buckets with collision handling via linked lists, upgraded to Red-Black trees in Java 8+ for O(log n) worst-case lookup. Explains hash function, bucket indexing, load factor, rehashing, and why immutable keys are critical to avoid retrieval failures.

• •HashMap uses array of buckets with linked list/Red-Black tree collision handling
• •Java 8+ optimization: tree structure kicks in at high collision counts for O(log n) performance
• •Immutable keys (String, Integer) are mandatory; mutable keys cause hashCode drift and unretrievable entries

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