What is an iterator and what is it used for?

An iterator in Java is an object that allows sequential traversal of the elements in a collection without needing to know its internal structure.

Main purposes of using an iterator:

• Abstraction: Provides a unified way to traverse elements for different types of collections (lists, sets, etc.).
• Safety: Allows removing elements from the collection during iteration without breaking the iteration logic.
• Independence: Traversal of elements is independent of the specific implementation of the collection.

The Iterator<E> interface defines three main methods:

• hasNext(): Returns true if there are more elements in the iteration.
• next(): Returns the next element in the iteration.
• remove(): Removes from the underlying collection the last element returned by the iterator.

Example of usage:

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

// Example of using an iterator
public class IteratorExample {

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

        Iterator<String> iterator = list.iterator();

        // Traversing elements using the iterator
        while (iterator.hasNext()) {
            String element = iterator.next();
            System.out.println(element);

            // Removing an element during iteration (example)
            if (element.equals("Banana")) {
                iterator.remove();
            }
        }

        System.out.println("List after removal: " + list);
    }
}