设计模式学习（十三） 迭代器模式

package com.lp.iterator;
//自定义的迭代器接口
public interface MyIterator {
    void first();//将游标指向第一个元素
    void next();//将游标指向下一个元素
    boolean hasNext();//判断是否存在下一个元素
    
    boolean isFirst();
    boolean isLast();
    
    Object getCurrentObj();//获取当前游标指向的对象
    
}

package com.lp.iterator;

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

//自定义的聚合类
public class ConcerteMyAggregete {
    private List<Object> list = new ArrayList<Object>();
    
    public void addObject(Object obj){
        this.list.add(obj);
    }
    
    public void removeObject(Object obj){
        this.list.add(obj);
    }

    public List<Object> getList() {
        return list;
    }

    public void setList(List<Object> list) {
        this.list = list;
    }
    
    //获得迭代器
    public MyIterator createIterator(){
        return new ConcreteIterator();
    }
    
    //使用内部类定义迭代器，可以直接使用外部类的属性
    private class ConcreteIterator implements MyIterator{

        private  int cursor; // 定义游标用于记录遍历时的位置
        
        @Override
        public void first() {
            cursor = 0;        
        }

        @Override
        public void next() {
            if(cursor < list.size()){
                cursor ++;
            }        
        }

        @Override
        public boolean hasNext() {
            if(cursor < list.size()){
                return true;
            }
            return false;
        }

        @Override
        public boolean isFirst() {
            if(cursor == 0 )
                return true;
            return false;
        }

        @Override
        public boolean isLast() {
            return cursor == (list.size() - 1 )?true:false;
        }

        @Override
        public Object getCurrentObj() {
            return list.get(cursor);
        }
        
    }
}

package com.lp.iterator;

public class Client {
    public static void main(String[] args){
        ConcerteMyAggregete cma = new ConcerteMyAggregete();
        cma.addObject("aa");
        cma.addObject("bb");
        cma.addObject("cc");
        
        MyIterator iter = cma.createIterator();
        while(iter.hasNext()){
            System.out.println(iter.getCurrentObj());
            iter.next();
        }
    }
}