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.

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

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。

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

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：

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