设计模式（第十七式：迭代器模式）

概念：
　　迭代器模式：Provide a way to access the elements of an aggregarte object sequentiaally with exposing its underlying representation. 提供一种访问容器对象内每个元素的一种方式，并且不暴露对象的一些内部细节。

实现：
　　迭代器接口定义

public interface Iterator {Object next();Boolean hasNext();
}

　　容器接口定义

public interface Box {void add(Object object);Iterator createIterator();
}

　　迭代器实现

public class BoxIterator implements Iterator {private BookBox bookBox;private Integer size;private Integer index;public BoxIterator(BookBox bookBox){this.bookBox = bookBox;this.size = bookBox.size();this.index = 0;}@Overridepublic Object next() {if(index<size){return bookBox.getElement(index++);}return null;}@Overridepublic Boolean hasNext() {return index<size;}
}

　　容器实现

public class BookBox implements Box {private Vector vector = new Vector();@Overridepublic void add(Object object) {this.vector.add(object);}public Object getElement(Integer index){if(index<vector.size()){return vector.get(index);}return null;}public Integer size(){return vector.size();}@Overridepublic Iterator createIterator() {return new BoxIterator(this);}
}

测试及结果：

@Test
public void iteratorTest() {BookBox bookBox = new BookBox();bookBox.add("历史书");bookBox.add("政治书");bookBox.add("语文书");bookBox.add("数学书");bookBox.add("英语书");Iterator iterator = bookBox.createIterator();while (iterator.hasNext()) {System.out.println(iterator.next());}
}