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Java Map Interface. A map contains values on the basis of key, i.e. key and value pair. Each key and value pair is known as an entry. A Map contains unique keys. A Map is useful if you have to search, update or delete elements on the basis of a key.
- HashMap
Java HashMap. Java HashMap class implements the Map...
- HashMap
- Creating Map Objects
- Methods in Java Map Interface
- Performing Operations Using Map Interface and Hashmap Class
- FAQs in Java Map Interface
Since Map is an interface, objects cannot be created of the type map. We always need a class that extends this map in order to create an object. And also, after the introduction of Genericsin Java 1.5, it is possible to restrict the type of object that can be stored in the Map. Syntax:Defining Type-safe Map
Example: Classes that implement the Map interface are depicted in the below media and described later as follows:
Since Map is an interface, it can be used only with a class that implements this interface. Now, let’s see how to perform a few frequently used operations on a Map using the widely used HashMap class. And also, after the introduction of Genericsin Java 1.5, it is possible to restrict the type of object that can be stored in the map.
import java.util.Map; import java.util.TreeMap; class Main { public static void main(String[] args) { // Creating Map using TreeMap Map<String, Integer> values = new TreeMap<>(); // Insert elements to map values.put("Second", 2); values.put("First", 1); System.out.println("Map using TreeMap: " + values); // Replacing the values values.replace ...
The Map Interface. A Map is an object that maps keys to values. A map cannot contain duplicate keys: Each key can map to at most one value. It models the mathematical function abstraction.
- size. int size() Returns the number of key-value mappings in this map. If the map contains more than Integer.MAX_VALUE elements, returns Integer.MAX_VALUE.
- isEmpty. boolean isEmpty() Returns true if this map contains no key-value mappings. Returns: true if this map contains no key-value mappings.
- containsKey. boolean containsKey(Object key) Returns true if this map contains a mapping for the specified key. More formally, returns true if and only if this map contains a mapping for a key k such that (key==null ?
- containsValue. boolean containsValue(Object value) Returns true if this map maps one or more keys to the specified value. More formally, returns true if and only if this map contains at least one mapping to a value v such that (value==null ?
Jun 14, 2019 · A Map is an object that maps keys to values, or is a collection of attribute-value pairs. It models the function abstraction in mathematics. The following picture illustrates a map: Note that a Map is not considered to be a true collection, as the Map interface does not extend the Collection interface.
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May 1, 2024 · Table of Content. What is Map Data Structure? Need for Map Data Structure. Properties of Map Data Structure. Map Data Structure in Different Languages. Maps in C++. Maps in Java. Maps in Python. Maps in C# Maps in JavaScript. Difference between Map, Set, and Array Data Structure. Internal Implementation of Map Data Structure.
