设计模式之迭代器模式

迭代器模式

提供一种方法顺序访问一个聚合对象中的各个元素，而不暴露该对象的内部表示

Iterator

package com.hml.iterator;

public interface Iterator {

    public Object first();
    
    public Object next();
    
    public boolean hasNext();
    
    public Object curItem();
    
    public void add(Object o);
}

Aggregate

package com.hml.iterator;

import java.util.ArrayList;
import java.util.List;

public  class Aggregate implements Iterator {

    private List<Object> items = new ArrayList<Object>();
    private int count = 0;
    public Object first() {
        return items.get(0);
    }

    public Object next() {
        return items.get(++count);
    }

    public boolean hasNext() {
        return count < items.size();
    }

    public Object curItem() {
        return items.get(count);
    }

    public void add(Object o) {
        items.add(o);
    }
}

Test

package com.hml.iterator;

public class Test {
    public static void main(String[] args) {
        Aggregate a = new Aggregate();
        a.add(1);
        a.add(2);
        a.add(3);
        
        System.out.println(a.curItem());
        System.out.println(a.next());
        System.out.println(a.first());
        System.out.println(a.hasNext());
    }
}

类图

当需要对聚合对象进行遍历时，可以考虑使用迭代器模式。