用处：集合的遍历

先上类图

迭代器模式.jpg

案例代码

简单实现ArrayList 和 LinkList

package com.wwj.iteartormode;

public class Main {
    public static void main(String[] args) {
        Collection_<String> test = new ArrayList_();
        test.add("1");
        test.add("2");
        test.add("3");
        Iteartor_ iteartor = test.iteartor();
        while (iteartor.hasNext()){
            System.out.println(iteartor.next());
        }

        Collection_<String> test2 = new LinkList_();
        test2.add("4");
        test2.add("5");
        test2.add("6");
        Iteartor_ iteartor2 = test2.iteartor();
        while (iteartor2.hasNext()){
            System.out.println(iteartor2.next());
        }

    }
}

/**
 * 集合接口
 */
interface Collection_<T>{
    void add(T o);
    int size();
    Iteartor_ iteartor();
}

/**
 * 遍历器
 */
interface Iteartor_{
    Boolean hasNext();
    Object next();
}

/**
 * 自定义ArrayList练习
 */
class ArrayList_<T> implements Collection_<T>{
    Object[] objects = new Object[10];
    private int index = 0;

    @Override
    public void add(T 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++;
    }

    @Override
    public int size(){
        return this.index;
    }

    @Override
    public Iteartor_ iteartor() {
        return new ArrayListIteartor();
    }

    /**
     * 定义自己的迭代器
     */
    private class ArrayListIteartor implements Iteartor_{

        private int currentIndex = 0;

        @Override
        public Boolean hasNext() {
            if(currentIndex >= index){
                return false;
            }
            return true;
        }

        @Override
        public T next() {
            Object object = objects[currentIndex];
            currentIndex++;
            return (T)object;
        }
    }
}

/**
 * 简单实现LinkList
 */
class LinkList_<T> implements Collection_<T>{
    Node head;
    Node tail;
    private int size = 0;

    @Override
    public void add(T o) {
        Node n = new Node(o);
        if(head == null){
            head = n;
        }else{
            tail.next = n;
        }
        tail = n;
        size++;
    }

    @Override
    public int size() {
        return this.size;
    }

    @Override
    public Iteartor_ iteartor() {
        return new LinkListIteartor();
    }

    /**
     * 定义node节点
     */
    protected class Node{
        private T object;
        Node next;

        public Node(T object) {
            this.object = object;
        }
    }

    /**
     * 定义自己的迭代器
     */
    private class LinkListIteartor implements Iteartor_{
        private int currentIndex = 0;
        private Node currentNode;

        @Override
        public Boolean hasNext() {
            if(currentIndex >= size){
                return false;
            }
            return true;
        }

        @Override
        public T next() {
            if (currentNode == null){
                currentNode = head;
            }else {
                currentNode = currentNode.next;
            }
            currentIndex++;
            return currentNode.object;
        }
    }
}