package com.test.DPs.XingWei.Iterator;

/**
 * 行為型：Iterator-迭代器		外觀：作用面為 物件
 * 
 * 用途：提供一種方法順序訪問一個聚合物件中各個元素，而又不需要暴露該物件的內部表示。
 * 理解：一是需要遍歷的物件，即聚集物件，
 *     二是迭代器物件，用於對聚集物件進行遍歷訪問
 */
interface Collection{
	Iterator iterator();
	Object get(int i);
	int size();
}
interface Iterator{
	Object previous();
	Object next();
	boolean hasNext();
	Object first();
}
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;  
    }  
}
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);  
    }  
}