Iterator in Java

An Iterator in Java is one of the most commonly used cursors in the Java Collections Framework. It is used to traverse or iterate through elements of a collection one by one.

• It is used to traverse elements in the forward direction only.
• Removes elements safely during traversal using remove().
• Iterator is a universal cursor that applies to all collection types — List, Set, and Queue.

Declaration of Iterator

public interface Iterator<E>

Here, E represents the type of elements to be iterated over.

Object Creation of Iterator

An Iterator object is created by calling the iterator() method on a collection object. Here, we will use an Iterator to traverse and print each element in an ArrayList.

Collection<String> names = new ArrayList<>();
Iterator<String> itr = names.iterator();

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

public class Geeks {
    public static void main(String[] args) {
      
        // Create an ArrayList and add some elements
        ArrayList<String> al = new ArrayList<>();
        al.add("A");
        al.add("B");
        al.add("C");

        // Obtain an iterator for the ArrayList
        Iterator<String> it = al.iterator();

        // Iterate through the elements and print each one
        while (it.hasNext()) {
          
            // Get the next element
            String n = it.next(); 
            System.out.println(n);      
        }
    }
}

A
B
C

Hierarchy of Iterator

Iterator is part of the java.util package and is implemented by all collection classes through their subinterfaces.