A HashMap is a part of Java ’s Collection Framework and implements the Map interface. It stores elements in key-value pairs, where, Keys are unique. and Values can be duplicated. Internally uses Hashing, hence allows efficient key-based retrieval, insertion, and removal with an average of O (1) time. In this article, we will understand the internal workings of the HashMap in Java , also how the get () and put () method functions, how hashing is done, how key-value pairs are stored and how the values are retrieved by keys. Basic Structure of a HashMap HashMap contains an array of Node objects. Each node represents a key-value mapping. This process is defined below: class Node { int hash; K key; V value; Node next; } Each node stores, hash: the hash code of the key key: the key object value ... Java HashMap A HashMap stores items in key/value pairs, where each key maps to a specific value. It is part of the java .util package and implements the Map interface. Instead of accessing elements by an index (like with ArrayList), you use a key to retrieve its associated value. A HashMap can store many different combinations, such as: Learn how Java HashMaps store and retrieve key-value pairs using hashing, index calculation, and collision handling. Understand the common operations, time complexities, and concurrent behavior of HashMaps.
