Java设计模式—迭代器(Iterator)

1.Aggregate接口所声明的方法只有iterator方法一个，这是为了建立一个对对应聚合的 
iterator 

Java代码 package com.pattern.iterator; public interface Aggregate { public abstract Iterator iterator(); } 2.iterator接口，执行元素递增，具有类似循环变量的功能。 Java代码 package com.pattern.iterator; public interface Iterator { public abstract boolean hasNext(); public abstract Object next(); } 3. 书籍类 Java代码 package com.pattern.iterator; public class Book { private String name=""; public Book(String name) { this.name = name; } /** * 获得书籍名称 * @return String */ public String getName() { return name; } } 4.书架类 Java代码 package com.pattern.iterator; /** * 书架类 * @author administrator */ 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]; } //添加书籍 public void appendBook(Book book) { this.books[last] = book; last++; } //获得书架存书的数量 public int getLength() { return books.length; } //获得书架迭代器对象 public Iterator iterator() { return new BookShelfIterator(this); } } 5.书架迭代器类 Java代码 package com.pattern.iterator; public class BookShelfIterator implements Iterator{ private BookShelf bookShelf; private int index; public BookShelfIterator(BookShelf bookShelf) { this.bookShelf = bookShelf; this.index = 0; } //检查是否还有下一本书 public boolean hasNext() { if(index < bookShelf.getLength()) { return true; } else { return false; } } //返回指定位置的书籍 public Object next() { Book book = bookShelf.getBookAt(index); index ++; return book; } } 6.测试类 Java代码 package com.pattern.iterator; public class Main { public static void main(String[] args) { //生成一个书架 BookShelf bookShelf = new BookShelf(4); //向书架添加书籍 bookShelf.appendBook(new Book("周恩来的晚年岁月")); bookShelf.appendBook(new Book("C++网络编程")); bookShelf.appendBook(new Book("J2EE网络编程精解")); bookShelf.appendBook(new Book("Java编程思想")); //获得书架迭代器 Iterator it = bookShelf.iterator(); while(it.hasNext()) { Book book = (Book)it.next(); System.out.println(book.getName()); } } }  输出结果: 

周恩来的晚年岁月 
C++网络编程 
J2EE网络编程精解 

迭代器设计恩想： 
      迭代器可以顺序访问一个聚集中的元素而不必显露聚集的内部对象。多个对象聚在一起形成的总体称为聚集，聚集对象是能够包容一组对象的容器对象。迭代器模式将迭代逻辑封装到一个独立的对象中，从而与聚集本身隔开。迭代算法独立于聚集对象，修改迭代算法不会对聚集对象产生任何影响，实现程序的松耦合。