1、类图关系

输入图片说明

2、代码例子

Iterator（迭代器）

package me.jtzen9.iterator;public interface Iterator {    boolean hasNext();    Object next();}

Aggregate（集合）

package me.jtzen9.iterator;public interface Aggregate {    Iterator iterator();}

Book类，集合存放的元素类

package me.jtzen9.iterator;public class Book {    private String name;    public Book(String name) {        this.name = name;    }    public String getName() {        return name;    }}

BookShelf类，即具体集合类

package me.jtzen9.iterator;public class BookShelf implements Aggregate{    private Book[] books;    private int last = 0;    public BookShelf(int maxsize) {        this.books = new Book[maxsize];    }    public Book getBookAt(int index){        return books[index];    }    public void appendBook(Book book){        this.books[last] = book;        last++;    }    public int getLength(){        return last;    }    public Iterator iterator() {        return new BookShelfIterator(this);    }}

BookShelfIterator类，即具体迭代器类

package me.jtzen9.iterator;public class BookShelfIterator implements Iterator {    private BookShelf bookShelf;    private int index;    public BookShelfIterator(BookShelf bookShelf) {        this.bookShelf = bookShelf;        this.index = 0;    }    @Override    public boolean hasNext() {        return index < bookShelf.getLength();    }    @Override    public Object next() {        Book book = bookShelf.getBookAt(index);        index++;        return book;    }}

测试代码：

package me.jtzen9.iterator;public class IteratorTest {    public static void main(String[] args) {        BookShelf bookShelf = new BookShelf(4);        bookShelf.appendBook(new Book("Around the world in 80 Days"));        bookShelf.appendBook(new Book("Bible"));        bookShelf.appendBook(new Book("Cinderella"));        bookShelf.appendBook(new Book("Daddy-Long-Legs"));        Iterator it = bookShelf.iterator();        while (it.hasNext()) {            Book book = (Book) it.next();            System.out.println(book.getName());        }    }}