迭代器模式，乱披风锤法，九九八十一锤！

​ 迭代器模式几乎可以说是最常用的设计模式了，这种模式我们随处可见，用于顺序的访问对象的元素而不需要底层实现。迭代器模式属于行为性模式的一种，这类设计模式特别关注对象之间的通信。

​ 常见的Iterator就是迭代器模式的一种，迭代器模式将存储数据和遍历数据的职责分离，但新增聚合类就需要增加对应的迭代器，在一定程度上增加了系统的复杂性。

类图：

具体代码实现：

public interface Aggregate {
    Iterator iterator();
}

public interface Iterator {
    public boolean hasNext();
    public Object next();
}

public class Milk {
    private String name;

    public Milk(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}


public class MilkList implements Aggregate {

    List milks;

    public MilkList() {
        this.milks = new ArrayList();
    }

    public Milk getMilk(int index) {
        return milks.get(index);
    }

    public void appendMilk(Milk milk) {
        milks.add(milk);
    }

    public int getLen() {
        return milks.size();
    }

    public Iterator iterator() {
        return new MilkListIterator(this);
    }
}

public class MilkListIterator implements Iterator {

    private int index;

    private MilkList milkList;

    public MilkListIterator(MilkList milkList) {
        this.milkList = milkList;
        this.index = 0;
    }

    public boolean hasNext() {
        if(index < milkList.getLen()) {
            return true;
        } else {
            return false;
        }
    }

    public Object next() {
        Milk milk = milkList.getMilk(index);
        index ++;
        return milk;
    }
}

public class Client {
    public static void main(String[] args) {
        MilkList milkList = new MilkList();
        milkList.appendMilk(new Milk("牛奶1号"));
        milkList.appendMilk(new Milk("牛奶2号"));
        milkList.appendMilk(new Milk("牛奶3号"));
        Iterator iterator = milkList.iterator();
        while(iterator.hasNext()) {
            Milk milk = (Milk) iterator.next();
            System.out.println(milk.getName());
        }
    }
}

​ 迭代器模式就介绍到这里啦，希望对你有所帮助！

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