Design Pattern - Iterator Pattern

Iterator Pattern

假設, 各種飲料店實作, 儲存資料的方式都不同時...

public class TeaBeverage{

    ArrayList allTea;
   
    public TeaBeverage{
       
        allTea = new ArrayList();
        Item item = new Item();
        item.setName("紅茶");
        allTea.add(item);
       
        item = new Item();
        item.setName("奶茶");
        allTea.add(item);
    }
   
    public ArrayList getAllItem(){
        return allTea;
    }
}

public class CafeBeverage{

    ArrAllCafe[] arrAllCafe;
   
    public CafeBeverage{
       
        arrAllCafe = new ArrAllCafe[2];
       
        Item item = new Item();
        item.setName("紅茶");
        arrAllCafe[0] = item;
       
        item = new Item();
        item.setName("奶茶");
        arrAllCafe[1] = item;
    }
   
    public ArrayList getAllItem(){
        return arrAllCafe;
    }
}

這時, 我們若要取出tea, cafe的所有資料, 它們return的類型是不同的

所以若這二個class能針對interface實現, 我們在使用時, 也針對這interface

好處:
1.把實作的儲存方式封裝起來
2.解藕

public interface IIterator{

    boolean hasNext();
    Object next();
}

public class CafeBeverageIterator implements IIterator{

    ArrAllCafe[] arrAllCafe;
    int position = 0;
       
    public CafeBeverageIterator(ArrAllCafe[] arrAllCafe){
        this.arrAllCafe = arrAllCafe;
    }
   
    public Object next(){
        Item item = arrAllCafe[position];
        position = position + 1;
        return item;
    }
   
    public boolean hasNext(){
        if(position >= arrAllCafe.length || arrAllCafe[position] == null){
            return false;
        }else{
            return true;
        }
    }
}

修改原本的CafeBeverage, 改成回傳Iterator interface

public class CafeBeverage{

    //同上
   
    //public ArrayList getAllItem(){
        //return arrAllCafe;
    //}
   
    public IIterator createIterator(){
        return CafeBeverageIterator(arrAllCafe);
    }
}

未完