What are the differences between HashMap, LinkedHashMap, and TreeMap in terms of data storage and sorting?

HashMap, LinkedHashMap, and TreeMap are implementations of the Map interface in Java, differing in how they store and order elements:

• HashMap — stores key-value pairs without any order. Fast insertion, deletion, and lookup (average O(1)), but the order of elements is not guaranteed.

• LinkedHashMap — extends HashMap, maintaining the order of insertion. This is achieved through a linked list that keeps track of the insertion order. Allows iteration over elements in insertion order.

• TreeMap — stores elements in a sorted order by key, using a red-black tree structure. Insertion, deletion, and search operations are performed in O(log n). Allows retrieving elements in sorted order.

Thus, the choice depends on requirements for order and performance:

• If fast access without order is needed — HashMap.
• If insertion order is important — LinkedHashMap.
• If a key-sorted order is required — TreeMap.