![]() ![]() ![]() HashMap is unsynchronised, therefore it's faster and uses less memory than HashTable. Here, keys are unique identifiers used to associate each value on a map. HashMap stores the data in (Key, Value) pairs. HashMap in Java is a collection that implements Map interface. In this article, we will see the uses of HashMap in Java, its internal working and examples. Since Java 5, it is denoted as HashMap, where K stands for Key and V for Value. Keys should be unique as the key is used to retrieve the corresponding value from the map. It stores the data in a key-value mapping in which every key is mapped to exactly one value of any data type. It provides the basic implementation of Map interface of Java. Static class Entry implements Map.HashMap in Java is a part of the collections framework, which is found in java.util package. It contains the hashcode of the key, key, value and the reference of the next Node. ![]() HashMap in Java internally uses an Array of Entries( Entry table) to store the key-value pairs.Each index of the above array is called a Bucket.For example, table is the referred as Bucket 0, table as Bucket 1 and so on.Įntry is an inner class of HashMap. Removes all key-value mappings from the map.Ĭopies all of the mappings from the specified map to this map. Returns a set of all key-value mappings in the map. Returns a collection of all values in the map. Returns the number of key-value mappings in the map. Removes the mapping for the specified key from the map. Returns true if the map contains the specified value. Returns true if the map contains the specified key. Returns the value to which the specified key is mapped. Its versatility makes it suitable for a wide range of use cases.Ĭommonly used methods of HashMap in Java are mentioned below MethodĪssociates the specified value with the specified key in the map. Wide Range of Applications: HashMap in Java is used in various areas of software development, including caching, indexing, data processing, and implementing associative arrays.Implementation of Hashing Algorithms: HashMap implements various hashing algorithms internally, ensuring efficient distribution and retrieval of elements, even for large data sets.It automatically adjusts its capacity to maintain efficient performance, making it suitable for handling dynamic data sets. Dynamic Size: HashMap dynamically resizes itself to accommodate more elements as needed.This makes it suitable for scenarios where data needs to be associated with specific identifiers. Flexible Key-Value Storage: HashMap in Java allows the storage of key-value pairs, where each key is unique. ![]() It uses hashing techniques to store and retrieve data in constant time complexity (O(1)) on average.
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