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迭代子模式（Iterator）
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???????? 顧名思義，迭代器模式就是順序訪問聚集中的對(duì)象，一般來說，集合中非常常見，如果對(duì)集合類比較熟悉的話，理解本模式會(huì)十分輕松。這句話包含兩層意思：一是需要遍歷的對(duì)象，即聚集對(duì)象，二是迭代器對(duì)象，用于對(duì)聚集對(duì)象進(jìn)行遍歷訪問。我們看下關(guān)系圖：
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public interface Collection { public Iterator iterator(); /*取得集合元素*/ public Object get(int i); /*取得集合大小*/ public int size();
}
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public?interface?Iterator?{?? ????//前移?? ????public?Object?previous();?? ?????? ????//后移?? ????public?Object?next();?? ????public?boolean?hasNext();?? ?????? ????//取得第一個(gè)元素?? ????public?Object?first();?? }??
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public?class?MyCollection?implements?Collection?{?? ?? ????public?String?string[]?=?{"A","B","C","D","E"};?? ????@Override?? ????public?Iterator?iterator()?{?? ????????return?new?MyIterator(this);?? ????}?? ?? ????@Override?? ????public?Object?get(int?i)?{?? ????????return?string[i];?? ????}?? ?? ????@Override?? ????public?int?size()?{?? ????????return?string.length;?? ????}?? }??
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public?class?MyIterator?implements?Iterator?{?? ?? ????private?Collection?collection;?? ????private?int?pos?=?-1;?? ?????? ????public?MyIterator(Collection?collection){?? ????????this.collection?=?collection;?? ????}?? ?????? ????@Override?? ????public?Object?previous()?{?? ????????if(pos?>?0){?? ????????????pos--;?? ????????}?? ????????return?collection.get(pos);?? ????}?? ?? ????@Override?? ????public?Object?next()?{?? ????????if(pos<collection.size()-1){?? ????????????pos++;?? ????????}?? ????????return?collection.get(pos);?? ????}?? ?? ????@Override?? ????public?boolean?hasNext()?{?? ????????if(pos<collection.size()-1){?? ????????????return?true;?? ????????}else{?? ????????????return?false;?? ????????}?? ????}?? ?? ????@Override?? ????public?Object?first()?{?? ????????pos?=?0;?? ????????return?collection.get(pos);?? ????}?? ?? }??
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public?class?Test?{?? ?? ????public?static?void?main(String[]?args)?{?? ????????Collection?collection?=?new?MyCollection();?? ????????Iterator?it?=?collection.iterator();?? ?????????? ????????while(it.hasNext()){?? ????????????System.out.println(it.next());?? ????????}?? ????}?? }??
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