Why prefer ArrayDeque over Stack and LinkedList, and List.of over Collections.unmodifiableList?

Stack extends Vector and synchronizes every operation for no benefit in single-threaded code, while LinkedList suffers cache-unfriendly pointer chasing and per-node object overhead; ArrayDeque is a contiguous, unsynchronized ring buffer that is faster for both stack and queue use.

For immutability, List.of returns a genuinely immutable list that also rejects nulls, whereas Collections.unmodifiableList returns a read-only view over a backing list, so if someone holds the backing list they can still mutate it underneath you. Prefer the truly immutable factory when you want a real guarantee.