設計模式-迭代器模式

迭代器設計模式爲我們提供一種順序訪問容器內部元素的方法，並且同時不對外暴露出內部的結構。
實現迭代器需要繼承Ierrator接口，並且覆寫hasNext和next方法。還可以覆寫remove方法。

例如：

package designPattern;

import java.util.Iterator;

/**
 * Created by 18760 on 2017/11/23.
 */

class ABC{
    String name;
    public ABC(String name){
        this.name = name;
    }
    public String toString(){ return this.name;}
}

class Menu implements Iterator{
    ABC[] context;
    int position = 0;

    public Menu(ABC[] context){
        this.context = context;
    }

    public Object next(){
        ABC object = context[position];
        position++;
        return object;
    }

    public boolean hasNext(){
        if (position>=context.length){
            return false;
        }
        if (context[position]==null){
            return false;
        }
        return true;
    }

    public void remove(){
        if (position <= 0) {
            throw new IllegalStateException("You can't remove've done at least one next()");
        }
        if (context[position - 1] != null) {
            for (int i = position-1; i < (context.length - 1); i++) {
                context[i] = context[i + 1];
            }
            context[context.length - 1] = null;
        }
    }
}

public class Iter {

    public static void main(String[] args){
        ABC a = new ABC("ASFD");
        ABC b = new ABC("ASDFKJ");
        ABC c = new ABC("sfgasdg");
        ABC d = new ABC("ASDG");
        ABC[] context = {a, b, c, d};
        Menu menu = new Menu(context);
        while (menu.hasNext()){
            System.out.println((ABC)menu.next());
            int i = 1;
            if (i==1){
                menu.remove();
                i = i + 1;
            }
        }

    }
}