Java设计模式之Iterator模式

分类： 【java】2013-07-15 10:58 917人阅读 评论(0) 收藏 举报
所谓Iterator模式，即是Iterator为不同的容器提供一个统一的访问方式。本文以java中的容器为例，模拟Iterator的原理。
参考：马士兵 Java设计模式 Iterator
1.首先定义一个容器Collection接口.

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package com.njupt.zhb.learn.iterator;

public interface Collection {

void add(Object o);

int size();

Iterator iterator();

}

2.定义一个Iterator迭代器的接口

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package com.njupt.zhb.learn.iterator;

public interface Iterator {

Object next();

boolean hasNext();

}

3.定义一个ArrayList，实现Collection接口，并写一个实现了Iterator接口的内部类。

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package com.njupt.zhb.learn.iterator;

import com.njupt.zhb.learn.iterator.Collection;

public class ArrayList implements Collection {

Object[] objects = new Object[10];

int index = 0;

public void add(Object o) {

if(index == objects.length) {

Object[] newObjects = new Object[objects.length * 2];

System.arraycopy(objects, 0, newObjects, 0, objects.length);

objects = newObjects;

}

objects[index] = o;

index ++;

}

public int size() {

return index;

}

public Iterator iterator() {

return new ArrayListIterator();

}

private class ArrayListIterator implements Iterator {

private int currentIndex = 0;

@Override

public boolean hasNext() {

if(currentIndex >= index) return false;

else return true;

}

@Override

public Object next() {

Object o = objects[currentIndex];

currentIndex ++;

return o;

}

}

}

4.编写测试程序TestMain

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package com.njupt.zhb.learn.iterator;

import com.njupt.zhb.learn.iterator.ArrayList;

public class TestMain {

public static void main(String[] args) {

Collection c = new ArrayList();

for(int i=0; i<15; i++) {

c.add("string "+i);

}

System.out.println(c.size());

Iterator it = c.iterator();

while(it.hasNext()) {

Object o = it.next();

System.out.println(o.toString() + " ");

}

}

}

运行结果：

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15

string 0

string 1

string 2

string 3

string 4

string 5

string 6

string 7

string 8

string 9

string 10

string 11

string 12

string 13

string 14

从以上可以看出，设计模式到处用到面向对象中的多态。接口调用子类中的函数。源代码下载：
http://download.csdn.net/detail/nuptboyzhb/5755295