1 /* Example of IteratorPattern
   2  */
   3 import java.util.Vector;
   4 
   5 interface Aggregate {
   6     public abstract Iterator iterator();
   7 }
   8 
   9 interface Iterator {
  10     public abstract boolean hasNext();
  11     public abstract Object next();
  12 }
  13 
  14 class Book {
  15     private String name = "";
  16     public Book(String name) {
  17         this.name = name;
  18     }
  19     public String getName() {
  20         return name;
  21     }
  22 }
  23 
  24 class BookShelf implements Aggregate {
  25     private Vector books;
  26     public BookShelf(int initialsize) {
  27         this.books = new Vector(initialsize);
  28     }
  29     public Book getBookAt(int index) {
  30         return (Book)books.get(index);
  31     }
  32     public void appendBook(Book book) {
  33         books.add(book);
  34     }
  35     public int getLength() {
  36         return books.size();
  37     }
  38     public Iterator iterator() {
  39         return new BookShelfIterator(this);
  40     }
  41 }
  42 
  43 class BookShelfIterator implements Iterator {
  44     private BookShelf bookShelf;
  45     private int index;
  46     public BookShelfIterator(BookShelf bookShelf) {
  47         this.bookShelf = bookShelf;
  48         this.index = 0;
  49     }
  50     public boolean hasNext() {
  51         if(index < bookShelf.getLength()) {
  52             return true;
  53         } else {
  54             return false;
  55         }
  56     }
  57     public Object next() {
  58         Book book = bookShelf.getBookAt(index);
  59         index++;
  60         return book;
  61     }
  62 }
  63 
  64 public class IteratorBookShelf {
  65     public static void main(String[] args) {
  66         BookShelf bookShelf = new BookShelf(4);
  67         bookShelf.appendBook(new Book("Around the World in 80 days"));
  68         bookShelf.appendBook(new Book("Bible"));
  69         bookShelf.appendBook(new Book("Cinderella"));
  70         bookShelf.appendBook(new Book("Daddy-Long-Legs"));
  71         Iterator it = bookShelf.iterator();
  72         while(it.hasNext()) {
  73             Book book = (Book)it.next();
  74             System.out.println(" "+book.getName());
  75         }
  76     }
  77 }