デザインパターン「Iterator」 ref: http://qiita.com/shoheiyokoyama/items/3f42d0057d9d5a861039

Aggregate.java

public interface Aggregate {
    public abstract Iterator iterator();
}

Book.java

public class Book {
    private String name;

    public Book(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }
}

BookShelf.java

import java.util.ArrayList;

public class BookShelf implements Aggregate {
    private ArrayList books;

    public BookShelf(int initialize) {
        this.books = new ArrayList(initialize);
    }

    public Book getBookAt(int index) {
        return (Book)books.get(index);
    }

    public void appendBook(Book book) {
        books.add(book);
    }

    public int getLength() {
        return books.size();
    }

    public Iterator iterator() {
        return new BookShelfIterator(this);
    }
}

BookShelfIterator.java

public class BookShelfIterator implements Iterator {
    private BookShelf bookShelf;
    private int index;

    public BookShelfIterator(BookShelf bookShelf) {
        this.bookShelf = bookShelf;
        this.index = 0;
    }

    public boolean hasNext() {
        if (index < bookShelf.getLength()) {
            return true;
        } else {
            return false;
        }
    }

    public Object next() {
        Book book = bookShelf.getBookAt(index);
        index++;
        return book;
    }
}

file6.java

Git Hub
Qiita
Java
Iterator pattern

file8.java

Git Hub
Qiita
Java
Iterator pattern

Iterator.java

public interface Iterator {
    public abstract boolean hasNext();
    public abstract Object next();
}

Main.java

public static void main(String[] args) {
        BookShelf bookShelf = new BookShelf(4);

        bookShelf.appendBook(new Book("Git Hub"));
        bookShelf.appendBook(new Book("Qiita"));
        bookShelf.appendBook(new Book("Java"));
        bookShelf.appendBook(new Book("Iterator pattern"));

        Iterator iterator = bookShelf.iterator();
        while(iterator.hasNext()) {
            Book book = (Book)iterator.next();
            System.out.println(book.getName());
        }
    }