Mar 7, 2025 · HashMap allows for efficient key-based retrieval, insertion, and removal with an average O (1) time complexity. Example: {...} It takes two parameters namely as follows: Note: Keys and value can’t be primitive datatype.

Example. Create a HashMap object called capitalCities that will store String keys and String values: import java.util.HashMap; // import the HashMap class HashMap<String, String> capitalCities = new HashMap<String, String>();

The HashMap class provides the functionality of the hash table data structure in Java. In this tutorial, we will learn about the Java HashMap class and its various operations with the help of examples.

Jan 16, 2025 · In this tutorial, we’ll see how to use HashMap in Java, and we’ll look at how it works internally. A class very similar to HashMap is Hashtable. Please refer to a couple of our other articles to learn more about the java.util.Hashtable class itself and the differences between HashMap and Hashtable. 2. Basic Usage.

Dec 5, 2024 · The HashMap, part of the Java Collections framework, is used to store key-value pairs for quick and efficient storage and retrieval operations.

Dec 14, 2015 · 1) Explain the different ways of creating HashMap in java? Below example shows 4 different methods for creating HashMap. 2) How do you add key-value pairs to HashMap? By using put () and putAll () methods. put () method adds key-value pair one by one where as putAll () method copies all key-value pairs from one HashMap to another HashMap. Output :

Nov 22, 2021 · A quick guide to Java API HashMap methods and Understand how it works internally with examples.

HashMap is a part of the Java Collections Framework and provides the implementation of the Map interface. It is used to store key-value pairs and allows for fast retrieval based on the key.

Feb 10, 2013 · In this Java tutorial, we will see different examples of HashMap, like adding and removing entries, iterating over Java HashMap, checking size map, finding if a key or value exists on Map, and various other examples, which we used frequently.

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.