intermediate~5h
Map Internals: Buckets, Hashing, and HashMap's Resize Dance
What actually happens inside a HashMap on put() and get() -- bucket selection, collision handling, Java 8's treeification of overloaded buckets, and the load-factor-driven resize that keeps average-case lookups fast.
Learning objectives
- Explain how HashMap converts a key's hashCode() into a bucket index, including the supplemental hash spreading function
- Describe how collisions within a bucket are handled before and after Java 8's treeification threshold
- State HashMap's load factor and resize trigger, and why both exist as a speed/memory trade-off
- Trace through a put() and a get() call step by step against the bucket array
- Explain why a mutable key is dangerous to use in a HashMap
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Map Internals: Buckets, Hashing, and HashMap's Resize Dance