Collections Interview Questions

**ArrayList**: - Uses dynamic array implementation. - Fast random access (get) - O(1). - Slow manipulation (add/remove in middle) - O(n) due to shifting. - Better for storing and accessing data. **LinkedList**: - Uses doubly linked list implementation. - Slow random access - O(n). - Fast manipulation (add/remove) - O(1) if you have the node reference. - Better for manipulating data frequently.

HashMap uses **hashing** to store and retrieve elements. 1. **put(K, V)**: - Calculates hash of Key. - Determines bucket index using `hash & (n-1)`. - If bucket empty, stores Node. - If collision, uses Linked List (or Red-Black Tree in Java 8+ if chain > 8) to store. 2. **get(K)**: - Calculates hash. - Goes to bucket. - Traverses list/tree comparing keys using `equals()`.