The Collection interface provides support for the implementation of a mathematical bag – an unordered collection of objects that may contain duplicates.

In Java, the Collection interface is a part of the Java Collections Framework and is present in the java.util package. It is at the top of the hierarchy of collection interfaces. The Collection interface represents a group of objects, known as elements. It provides a standard set of methods to manipulate collections, such as adding, removing, and querying elements.

Some common methods provided by the Collection interface include add, remove, contains, size, isEmpty, and iterator. Implementations of the Collection interface include classes like ArrayList, LinkedList, HashSet, and others.

Here’s a simple example of using the Collection interface:

java

import java.util.Collection;

import java.util.ArrayList;
public class CollectionExample {

    public static void main(String[] args) {

        // Creating a collection (ArrayList) of integers

        Collection<Integer> numbers = new ArrayList<>();
        // Adding elements to the collection

        numbers.add(1);

        numbers.add(2);

        numbers.add(3);
        // Displaying the elements of the collection

        System.out.println("Collection elements: " + numbers);
        // Removing an element from the collection

        numbers.remove(2);

// Displaying the modified collection System.out.println("Modified collection: " + numbers); } }

In this example, an ArrayList is used to implement the Collection interface, and various methods of the Collection interface are demonstrated.