标签：迭代 str ret 模式 code 是什么 rri arraylist style
迭代器模式：提供一个方法顺序访问一个聚合对象中的各个元素，而又不暴露该对象的内部表示。
当需要访问一个聚集对象，而不管这些对象是什么都需要遍历的时候，就应该考虑使用迭代器模式。当需要对聚集有多种方式遍历时，可以考虑使用迭代器模式。
Iterator迭代器抽象类：
public abstract class Iterator { public abstract Object first(); public abstract Object next(); public abstract boolean isDone(); public abstract Object currentItem(); }
Aggregate聚集抽象类：
public abstract class Aggregate { public abstract Iterator createIterator(); }
public class ConcreteAggregate extends Aggregate{ private List<Object> items = new ArrayList<Object>(); @Override public Iterator createIterator() { // TODO Auto-generated method stub return new ConcreteIterator(this); } public int count(){ return this.items.size(); } public Object getItemByIndex(int index){ return items.get(index); } public List<Object> getItems() { return items; } public void setItems(List<Object> items) { this.items = items; } }
public class ConcreteIterator extends Iterator{ private ConcreteAggregate aggregate; private int current = 0; public ConcreteIterator(ConcreteAggregate aggregate){ this.aggregate = aggregate; } @Override public Object first() { // TODO Auto-generated method stub return aggregate.getItemByIndex(0); } @Override public Object next() { // TODO Auto-generated method stub Object ret = null; current++; if(current < aggregate.count()){ ret = aggregate.getItemByIndex(current); } return ret; } @Override public boolean isDone() { // TODO Auto-generated method stub return current >= aggregate.count() ? true : false; } @Override public Object currentItem() { // TODO Auto-generated method stub return aggregate.getItemByIndex(current); } }
public class ConcreteIteratorDesc extends Iterator{ private ConcreteAggregate aggregate; private int current = 0; public ConcreteIteratorDesc(ConcreteAggregate aggregate){ this.aggregate = aggregate; current = this.aggregate.count() -1; } @Override public Object first() { // TODO Auto-generated method stub return aggregate.getItemByIndex(aggregate.count() -1); } @Override public Object next() { // TODO Auto-generated method stub Object ret = null; current--; if(current > 0){ ret = aggregate.getItemByIndex(current); } return ret; } @Override public boolean isDone() { // TODO Auto-generated method stub return current < 0 ? true : false; } @Override public Object currentItem() { // TODO Auto-generated method stub return aggregate.getItemByIndex(current); } }
public class Test { public static void main(String[] args){ Object[] strArr = new Object[]{"xiaohei","xiaobai","xx","sfedd"}; List<Object> passenger = Arrays.asList(strArr); ConcreteAggregate ca = new ConcreteAggregate(); ca.setItems(passenger); // Iterator iterator = ca.createIterator(); // Iterator iterator = new ConcreteIterator(ca); Iterator iterator = new ConcreteIteratorDesc(ca); while(!iterator.isDone()){ System.out.println(iterator.currentItem() + "请买票"); iterator.next(); } } }
迭代器模式就是分离了聚合对象的遍历行为，抽象出一个迭代器类来负责，这样既可以做到不暴露集合的内部结构，又可以让外部代码透明地访问集合内部的数据。
标签：迭代 str ret 模式 code 是什么 rri arraylist style
原文地址：https://www.cnblogs.com/shicaiyou/p/9353858.html
