Java Collection Interface Example

The Collection interface in Java provides the foundation for several other important interfaces, such as List, Set, and Queue. It represents a group of objects that can be treated as a single unit.

Collection Interface Overview

The Collection interface defines a set of methods for adding, removing, and manipulating elements in the collection. It also includes methods for determining the size of the collection, checking if the collection contains a specific element, and iterating over the elements in the collection.

Some of the key methods defined in the Collection interface include:

• add(): Adds an element to the collection
• remove(): Removes an element from the collection
• size(): Returns the number of elements in the collection
• contains(): Returns true if the collection contains the specified element
• iterator(): Returns an iterator over the elements in the collection

Other interfaces like List, Set, and Queue extend the Collection interface and add additional functionality. For example, List allows for indexed access and maintains the order of the elements in the collection, while Set does not allow for duplicates.

Collection Interface Example

This is a Java program that demonstrates how to use a Collection interface in Java. The program uses an ArrayList to store a collection of fruits, performs some basic operations on it, and prints the results to the console.

package com.java.collections.interfaces;

import java.util.ArrayList;
import java.util.Collection;

public class CollectionDemo {

    public static void main(String[] args) {

        Collection < String > fruitCollection = new ArrayList < > ();
        fruitCollection.add("banana");
        fruitCollection.add("apple");
        fruitCollection.add("mango");
        System.out.println(fruitCollection);

        fruitCollection.remove("banana");
        System.out.println(fruitCollection);

        System.out.println(fruitCollection.contains("apple"));

        fruitCollection.forEach((element) - > {
            System.out.println(element);
        });

        fruitCollection.clear();

        System.out.println(fruitCollection);
    }
}

Here's a step-by-step explanation of what the program does:

1. The main method creates a new ArrayList of strings called fruitCollection.
2. The add method is used to add three strings ("banana", "apple", and "mango") to the fruitCollection.
3. The println method is used to print the entire fruitCollection to the console.
4. The remove method is used to remove the string "banana" from the fruitCollection.
5. The println method is used to print the updated fruitCollection to the console.
6. The contains method is used to check if the fruitCollection contains the string "apple". The result is printed to the console.
7. The forEach method is used to iterate over each element in the fruitCollection. For each element, the println method is used to print the element to the console.
8. The clear method is used to remove all elements from the fruitCollection.
9. The println method is used to print the empty fruitCollection to the console.

When the program is run, it will output the following to the console:

[banana, apple, mango]
[apple, mango]
true
apple
mango
[]