Popular
Data Science
Technology
Finance
Management
Future Tech
The ‘Map’ interface represents a collection of key-value pairs. Each key in the map is associated with exactly one value, creating a relationship between the two. Keys in a map are unique, meaning no two entries can have the same key. Unlike other collection types, like lists and sets, which handle individual elements. A map organises data as pairs, where each unique key is associated with a specific value. This article explores the ‘Map’ interface, its features, and its common implementation.
The Java ‘Map’ interface is part of the Java Collection framework. It provides a way to store key-value pairs. Unlike lists or sets, which only store values, a’ Map’ associates each key with a specific value. This makes it easier to look up data based on a key.
The ‘Map’ interface in Java is a versatile tool for handling collections of data where each element is stored as a key-value pair. Here are some of the key features:
The ‘Map’ interface in Java is part of the Java Collection Framework and represents a collection of key-value pairs. It provides a blueprint for how key-value pairs are managed, and several classes implement this interface to provide different types of map behaviours. Here’s an overview of the hierarchy of the ‘Map’ interface in the Java language.
Below is a diagram showing the standard map interface hierarchy:
Class | Description |
HashMap | HashMap implements the Map interface and does not maintain any specific order. |
LinkedHashMap | The implementation of Map is LinkedHashMap. It inherits the class HashMap. The insertion order is maintained. |
TreeMap | The map and the sorted map interfaces are implemented. In TreeMap, the order is always maintained in ascending order. |
Interface | Description |
Map | The Map is not allowed in a map. It allows duplicate values. |
SortedMap | In the sorted map, Elements can be traversed in the sorted order of their keys. |
Creating a map object in Java is very straightforward. However, we cannot create an object of the type map. We always need a class that extends this map to create an object. After they introduced Generics in Java 1.5, it is possible to restrict the type of object that can be stored in the Map.
Syntax
The ‘Map’ interface in Java represents a collection that maps keys to values. A map cannot contain duplicate duplicate keys, and each key can map to at most one value. Here are some key characteristics of the ‘Map’ interface.
The ‘Map’ interface is useful when you need to store and retrieve data based on a unique key. Here are some common situations where you might choose to use a ‘map’.
Method | Action Performed |
put(key,value) | In this method, the Given value and key are associated together using this method. |
containsKey(key) | This method matches the key that exists in the map. This method returns true otherwise false. |
containsValue(Value) | This method matches the value that exists in the map. If the matches are found then returns true otherwise. IT returns false. |
isEmpty() | The map has no keys. This method returns true otherwise returns false. |
clear() | This method is used to clear all the elements in a map |
remove(key) | This method removes an entry for the given key |
remove(key,value) | The given values and their corresponding specified keys are removed from the map. |
entrySet() | It returns the set view, which includes each key and value. |
values() | This method contains the map and is returned as a collection view. |
putAll(Map) | This method is used to put the specified map into the map |
In this section, we explore some commonly performed operations on a Map interface. We will use the HashMap class, which implements the ‘Map’ interface using a hash table. It allows null values and the null key, which makes it unique among other ‘Map’ implementations like’ Hashtable’. Here are some operations that we will perform:
In Java, the put() method is used to add a new element to the map. However, the hashmap does not keep track of the insertion order. Internally, a unique has been generated for each element, and the elements are indexed based on this hash to increase efficiency. The time complexity for adding the element is O(1).
The following program demonstrates the adding elements in Java.
Program
Output
We also update an element after adding HashMap by using the put() method. The values of the keys Since the elements in the map are indexed using the keys. We can change the value of the key by simply inserting the new value. The time complexity for changing the element in O(1).
The following program demonstrates the program:
Program
Output
The remove() method can be used from the Map. If there is a mapping for a key in the map. We can remove the element from the map interface, which accepts the key value for removing the element from the Map. The time complexity for removing the element is O(1).
The following program demonstrates the removing element:
Program
Output
We can also iterate the map in a for-each loop. The getValue() method determines the key’s value and iterates through all the elements. The time complexity becomes O(n).
The following program demonstrates the Iterating Map:
Program
Output
The HashMap classes provide the basic implementation of the map. We can use a hashing method to access the values from the keys. It stores the elements as a key:value pair.
The following program demonstrates the HashMap class:
Progarm
Output
The LinkedHashMap class in Java is a part of the ‘java.util’ package and extends the ‘HashMap’ class. It maintains a doubly-linked list that defines the iteration ordering, which is typically the order in which elements are inserted into the map. The following program demonstrates the LinkedHashMap
Program
Output
We can also implement the TreeMap in the Map Interface. It provides a fast way to sort the map and differs from HashMap and LinkedHashMap. The ‘TreeMap’ class is part of Java’s Collection Framework and implements the ‘Map’ interface. The following program demonstrates the TreeMap class in Java:
Program
Output
The Map interface in Java helps you store data as pairs of keys and values. It makes it easy to find, add or remove items based on their keys. Different types of Maps, like ‘HashMap’, ‘TreeMap’ and ‘LinkedHashMap’. This offers different benefits, such as faster lookups or keeping items in order when they are added.
The DevOps Playbook
Simplify deployment with Docker containers.
Streamline development with modern practices.
Enhance efficiency with automated workflows.
Popular
Data Science
Technology
Finance
Management
Future Tech
Accelerator Program in Business Analytics & Data Science
Integrated Program in Data Science, AI and ML
Certificate Program in Full Stack Development with Specialization for Web and Mobile
Certificate Program in DevOps and Cloud Engineering
Certificate Program in Application Development
Certificate Program in Cybersecurity Essentials & Risk Assessment
Integrated Program in Finance and Financial Technologies
Certificate Program in Financial Analysis, Valuation and Risk Management
© 2024 Hero Vired. All rights reserved