How do implementations of LinkedHashMap, TreeHashMap, and HashMap differ in terms of their internal structure and behavior?

HashMap is an implementation of a hash table that stores key-value pairs without guaranteeing the order of elements. It uses an array of buckets, where each bucket contains a linked list or a tree (since Java 8) to resolve collisions. Insertion, search, and deletion operate on average in O(1).

LinkedHashMap extends HashMap by adding a doubly linked list to preserve the insertion order (or access order if access-order mode is enabled). This allows iteration over elements in a predictable order while maintaining operational efficiency.

TreeMap (the question mentions TreeHashMap, likely a typo) implements a data structure based on a red-black tree, where elements are stored in sorted order by key. Insertion, search, and deletion operate in O(log n). Unlike HashMap and LinkedHashMap, TreeMap does not use hashing but relies on key comparison.

In summary:

• HashMap: unordered, fast hash table.
• LinkedHashMap: like HashMap but preserves insertion or access order.
• TreeMap: a tree-based, sorted structure by key, slower but with guaranteed order.