Java设计模式—迭代器(Iterator)

Java设计模式—迭代器(Iterator)

转自（http://blog.163.com/nonoliuhao@126/blog/static/1716520942010101131346478/）

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;

publicinterface Aggregate {

publicabstract Iterator iterator();

}

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;

publicinterface Iterator {

publicabstractboolean hasNext();

publicabstract Object next();

}

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;

publicclass Book {

private String name="";

public Book(String name) {

this.name = name;

}

/**

* 获得书籍名称

* @return String

*/

public String getName() {

return name;

}

}

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

*/

publicclass BookShelf implements Aggregate{

private Book[] books;

privateint last = 0;

public BookShelf(int maxSize) {

this.books = new Book[maxSize];

}

public Book getBookAt(int index) {

return books[index];

}

//添加书籍

publicvoid appendBook(Book book) {

this.books[last] = book;

last++;

}

//获得书架存书的数量

publicint getLength() {

return books.length;

}

//获得书架迭代器对象

public Iterator iterator() {

returnnew BookShelfIterator(this);

}

}

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;

publicclass BookShelfIterator implements Iterator{

private BookShelf bookShelf;

privateint index;

public BookShelfIterator(BookShelf bookShelf) {

this.bookShelf = bookShelf;

this.index = 0;

}

//检查是否还有下一本书

publicboolean hasNext() {

if(index < bookShelf.getLength()) {

returntrue;

}

else {

returnfalse;

}

}

//返回指定位置的书籍

public Object next() {

Book book = bookShelf.getBookAt(index);

index ++;

return book;

}

}

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;

publicclass Main {

publicstaticvoid 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());

}

}

}

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 Java编程思想
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。