Java Collections Framework

Lecture 73:-  Java Collections Framework

The Java Collections Framework is a set of classes and interfaces in Java that provides an organized and efficient way to store, manage, and manipulate groups of objects (collections). It offers a wide range of data structures and algorithms to work with collections, making it easier for developers to perform common operations on data.

The key components of the Java Collections Framework are as follows:

1. Interfaces:
   • Collection: The root interface of the collections framework. It defines the basic operations that all collections should support, such as adding, removing, and searching for elements.
   • List: An ordered collection that allows duplicate elements. It provides methods to access elements by index.
   • Set: A collection that does not allow duplicate elements. It enforces uniqueness of elements.
   • Queue: A collection used to hold elements before processing. It follows the FIFO (First-In-First-Out) or priority-based order.
   • Map: A key-value pair collection that maps keys to values. It does not allow duplicate keys.
2. Classes:
   • ArrayList: A dynamic array-based implementation of the List interface.
   • LinkedList: A doubly-linked list implementation of the List interface.
   • HashSet: A hash table-based implementation of the Set interface. It uses the hash code of elements to maintain uniqueness.
   • TreeSet: A Red-Black tree-based implementation of the Set interface. It maintains elements in sorted order.
   • HashMap: A hash table-based implementation of the Map interface. It uses key-value pairs to store data.
   • TreeMap: A Red-Black tree-based implementation of the Map interface. It maintains keys in sorted order.
3. Algorithms and Utilities: The collections framework provides various utility methods in the Collections class to perform common operations on collections, such as sorting, searching, reversing, and shuffling elements.

The Java Collections Framework promotes code reusability and follows object-oriented principles by using interfaces and classes to abstract the behavior of different collection types. It also provides flexibility, as you can choose the appropriate data structure and implementation based on your application's requirements.

Example of using the Java Collections Framework:

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import java.util.ArrayList; import java.util.Collections; public class CollectionsExample {    public static void main(String[] args) {        // Creating and adding elements to ArrayList        ArrayList<Integer> numbers = new ArrayList<>();        numbers.add(5);        numbers.add(2);        numbers.add(8);        numbers.add(3);        // Sorting the ArrayList        Collections.sort(numbers);        // Printing sorted elements        for (int num : numbers) {            System.out.println(num);        }    } }

Output:

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2 3 5 8

In this example, we use the ArrayList class (a part of the Java Collections Framework) to create and store a list of integers. We then use the Collections.sort() method to sort the elements of the list in ascending order and print the sorted elements.