Iterator

The Iterator interface in Java provides a way to traverse through a collection of objects one by one. It is part of the java.util package and is commonly used in conjunction with the Collection framework. The Iterator interface defines three methods:

1. boolean hasNext(): returns true if there are more elements in the collection being iterated over.
2. E next(): returns the next element in the collection being iterated over.
3. void remove(): removes the last element returned by the iterator.

Here is an example of how to use an Iterator to iterate over a List:

import java.util.*;

public class IteratorExample {
    public static void main(String[] args) {
        List<String> myList = new ArrayList<String>();
        myList.add("apple");
        myList.add("banana");
        myList.add("cherry");

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

        while (iterator.hasNext()) {
            String element = iterator.next();
            System.out.println(element);
        }
    }
}

The hasNext() method is called in the while loop to check if there are more elements in the List to iterate over. The next() method is called to retrieve the next element in the List and assign it to the element variable. Finally, the remove() method can be called to remove the last element returned by the Iterator.

Iterators can also be used with other types of collections, such as Sets and Maps. In addition to the Iterator interface, Java also provides the ListIterator interface, which extends the Iterator interface to allow for bidirectional traversal of Lists.