The Iterator design pattern is a behavioral design pattern that provides a way

to access the elements of an aggregate object sequentially without exposing its underlying representation.

It allows clients to iterate over a collection of objects in a standardized manner,

abstracting away the details of the iteration process.

// Step 1: Iterator interface
interface Iterator<T> {
boolean hasNext();
T next();
}

// Step 2: Concrete Iterator
class ListIterator<T> implements Iterator<T> {
private List<T> list;
private int index;

public ListIterator(List<T> list) {
this.list = list;
this.index = 0;
    }

@Override
public boolean hasNext() {
return index < list.size();
    }

@Override
public T next() {
return list.get(index++);
    }
}

// Step 3: Aggregate interface
interface Aggregate<T> {
Iterator<T> createIterator();
}

// Step 4: Concrete Aggregate
class ListAggregate<T> implements Aggregate<T> {
private List<T> list;

public ListAggregate() {
this.list = new ArrayList<>();
    }

public void add(T element) {
list.add(element);
    }

@Override
public Iterator<T> createIterator() {
return new ListIterator<>(list);
    }
}

// Step 5: Client code
public class IteratorPattern {
public static void main(String[] args) {
ListAggregate<String> aggregate = new ListAggregate<>();
aggregate.add("A");
aggregate.add("B");
aggregate.add("C");

Iterator<String> iterator = aggregate.createIterator();
while (iterator.hasNext()) {
System.out.println(iterator.next());
        }
    }
}

class Book {
 private String title;


 public Book(String title) {
 this.title = title;

    }


 public String getTitle() {
 return title;

    }

}





class BookIterator implements Iterator {
 private BookCollection collection;
 private int index;


 public BookIterator(BookCollection collection) {
 this.collection = collection;
 this.index = 0;

    }


 public boolean hasNext() {
 return index < collection.size();

    }


 public Object next() {
 return collection.get(index++);

    }

}



class BookCollection extends ArrayList<Book> {


 public Iterator<Book> getIterator() {
 return new BookIterator(this);

    }


 @Override
 public boolean add(Book e) {
 super.add(e);
 return true;

    }





}



public class BookIteratorTest  {
 public static void main(String[] args) {
 BookCollection collection = new BookCollection();
 collection.add(new Book("The Java Book"));
 collection.add(new Book("Design Patterns"));


 Iterator<Book> iterator = collection.getIterator();


 while (iterator.hasNext()) {
 Book book = iterator.next();
 System.out.println(book.getTitle());

        }

    }

}