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. Introduction In this article, you will learn what is a HashMap , how to create a HashMap , how to add new key-value pairs to a HashMap , how to remove keys from a HashMap , how to iterate over a HashMap , and how to create and store user-defined objects as keys in a HashMap , and much more. The HashMap class in Java is part of the Java Collections Framework and implements the Map interface. It provides the basic implementation of the Map interface of Java and is used to store data in the form of ... HashMap in Java is a part of the Java Collections Framework that stores data in key-value pairs. It implements the Map interface and uses a hash table internally to provide fast performance for insertion, deletion, and lookup operations (average time complexity O (1)). 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:
