LinkedHashMap
LinkedHashMap is a Java collection class that extends HashMap to maintain a predictable iteration order, typically the order in which entries were inserted (insertion-order) or accessed (access-order). It combines the fast key-value lookup of a hash table with the ordered traversal of a linked list, making it useful for scenarios where both efficient retrieval and order preservation are required. This data structure is part of the Java Collections Framework and is commonly used for caching, LRU (Least Recently Used) implementations, and maintaining sequences of operations.
Developers should use LinkedHashMap when they need a Map that provides constant-time performance for basic operations like get and put, while also maintaining a specific iteration order, such as for building caches where the order of access matters (e.g., LRU cache) or when processing data in the order it was added. It is particularly valuable in applications like web session management, where entries need to be tracked in insertion order, or in algorithms that require predictable traversal without the overhead of sorting.