Mid-levelMid (3–6 yrs)JavaSpring BootGoogleAmazonOracle
HashMap internals
Explain HashMap internals and what changed after Java 8.
Answers use simple, clear English.
Audio N/AQuick interview answer
HashMap uses an array of buckets. Colliding keys form a linked list; after Java 8, long collision chains convert to balanced trees (TreeNodes) for O(log n) worst-case. Capacity, load factor (0.75), and key hashCode/equals quality dominate performance.
Detailed answer
HashMap uses an array of buckets. Colliding keys form a linked list; after Java 8, long collision chains convert to balanced trees (TreeNodes) for O(log n) worst-case. Capacity, load factor (0.75), and key hashCode/equals quality dominate performance. ConcurrentHashMap is required for concurrent writes.
midsenior#collections#jvm