Java设计模式之Iterator模式介绍

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。点击下载源代码