迭代器模式
迭代器模式属于行为型模式，用来遍历容器的一种模式。
图解
角色
- 迭代器接口：定义hasNext方法和next方法
- 具体迭代器：实现hasNext方法和next方法
- 容器接口：定义返回一个迭代器的接口
- 具体容器：实现返回迭代器接口
案例
该案例以简单实现ArrayList和LinkedList来演示迭代器模式。整体思想是，不管是什么容器，必须实现获取迭代器的方法，和定义一个迭代器来遍历对应的容器。
public interface Iterable_<E> {Iterator_<E> iterator();
}public interface Collection_<E> extends Iterable_<E>{void add(E e);int size();
}public interface Iterator_<E> {boolean hasNest();E next();
}
ArrayList实现类
public class ArrayList_<E> implements Collection_<E>{private static final int initSize = 10;private Object [] objects = new Object[initSize];private int index = 0;@Overridepublic void add(E e) {if(index >= objects.length){Object[] newObjects = new Object[(int) (objects.length * 1.5)];System.arraycopy(objects,0,newObjects,0,newObjects.length);this.objects = newObjects;}else {objects[index] = e;}index++;}@Overridepublic int size() {return index;}@Overridepublic Iterator_<E> iterator() {return new ArrayIterator();}/** arrayList迭代器*/private class ArrayIterator<E> implements Iterator_<E>{int cursor;@Overridepublic boolean hasNest() {return cursor != index;}@Overridepublic E next() {E e= (E) objects[cursor];cursor ++;return e;}}
}
linkedList实现类
public class LinkedList_<E> implements Collection_<E>{private int size = 0;private Node<E> lastNode = null;private Node<E> handNode = null;@Overridepublic void add(E e) {Node<E> objectNode =new Node<>(e,null);if(lastNode == null){lastNode = objectNode;handNode = objectNode;}else {lastNode.next = objectNode;lastNode = objectNode;}this.size++;}@Overridepublic int size() {return size;}@Overridepublic Iterator_<E> iterator() {return new LinkedIterator();}private class LinkedIterator implements Iterator_<E>{int cursor = 0;Node<E> tempNode = null;@Overridepublic boolean hasNest() {return cursor != size;}@Overridepublic E next() {cursor++;if(cursor ==1){tempNode = handNode;return handNode.getValue();}else {return tempNode.next.getValue();}}}private class Node<E>{private E value;private Node<E> next;public Node(E value, Node<E> next) {this.value = value;this.next = next;}public void setNext(Node<E> next) {this.next = next;}public E getValue() {return value;}}
}
Test类
package com.shaoby.designpatterns.Iterator;public class Test {public static void main(String[] args) {Collection_<String> objectArrayList_ = new LinkedList_<>();objectArrayList_.add("111");objectArrayList_.add("222");objectArrayList_.add("333");Iterator_<String> iterator = objectArrayList_.iterator();while (iterator.hasNest()){System.out.println(iterator.next());}}
}
