Basically, a HashMap allows you to store items with identifiers. They are stored in a table format with the identifier being hashed using a hashing algorithm. Typically they are more efficient to retrieve items than search trees etc.

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.

Mar 7, 2025 · In Java, HashMap is part of the Java Collections Framework and is found in the java.util package. It provides the basic implementation of the Map interface in Java. HashMap stores data in (key, value) pairs. Each key is associated with a value, and you can access the value by using the corresponding key.

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 :

Java HashMap. In the ArrayList chapter, you learned that Arrays store items as an ordered collection, and you have to access them with an index number (int type). A HashMap however, store items in "key/value" pairs, and you can access them by an index of another type (e.g. a String). One object is used as a key (index) to another object (value).

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. In the key-value pair (also referred to as an entry) to be stored in HashMap, the key must be a unique object whereas values can be duplicated. The keys are used to perform fast lookups.

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

A hashmap is a data structure that pairs keys to values. It uses a hash function to calculate an index into an array of buckets, from which the desired value can be found. Simply put, it's like a real-world dictionary where you know the 'word' (key), and you quickly find its meaning' (value).

Apr 16, 2025 · Java hashmap a complete tutorial for beginners with examples, methods and functions, explanation of each class from java key value pair to put method. Check out the complete definition, examples part for each class method, map interface java, and creation of java hasmap from java key value pair put.

Sep 19, 2022 · HashMap is a Map based collection class that is used for storing Key & value pairs, it is denoted as HashMap<Key, Value> or HashMap<K, V>. HashMap in java, is similar to the Hashtable class except that it is unsynchronized and permits nulls (null values and null key).