1.首先定义一个容器Collection接口.
复制代码 代码如下:
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
复制代码 代码如下:
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。
复制代码 代码如下:
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
复制代码 代码如下:
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：
复制代码 代码如下:
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。点击下载源代码