Introduction to Java Collections

In Java, a Collection is a framework that provides an architecture to store and manipulate a group of objects. It includes various interfaces and classes that help in managing collections of data effectively.

• Dynamic size: Collections can grow and shrink as needed.
• Data Manipulation: Collections provide various methods for searching, sorting, and manipulating data.
• Ease of Use: High-level methods simplify common tasks like adding, removing, and iterating through elements.

1. List: An ordered collection that allows duplicate elements. Example: ArrayList, LinkedList.
2. Set: A collection that does not allow duplicate elements. Example: HashSet, TreeSet.
3. Map: A collection of key-value pairs, where keys are unique. Example: HashMap, TreeMap.

Java Collections framework comprises several interfaces:

• Collection: The root interface for the collection hierarchy.
• List: Extends Collection and represents an ordered collection.
• Set: Extends Collection and represents a collection that cannot contain duplicates.
• Map: Represents a collection of key-value pairs.

Example of using a List:

import java.util.ArrayList;
import java.util.List;

public class Example {
    public static void main(String[] args) {
        List fruits = new ArrayList<>();
        fruits.add("Apple");
        fruits.add("Banana");
        fruits.add("Cherry");

        for (String fruit : fruits) {
            System.out.println(fruit);
        }
    }
}

• Use interfaces (like List, Set, Map) rather than implementation classes for variable declaration.
• Choose the right implementation based on your use case (e.g., use ArrayList for fast access, LinkedList for frequent insertions).
• Be cautious with null values in collections.