迭代器模式 - 代码指南

本文档详细说明迭代器模式的代码实现和使用方法

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一、项目结构

iterator/
├── Iterator.java        # 迭代器接口
├── Aggregate.java       # 聚合接口
├── ConcreteIterator.java # 具体迭代器
└── ConcreteAggregate.java # 具体聚合

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二、代码详解

2.1 Iterator - 迭代器接口

package com.linsir.designpattern.iterator;

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

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2.2 Aggregate - 聚合接口

package com.linsir.designpattern.iterator;

public interface Aggregate {
    Iterator createIterator();
}

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2.3 ConcreteIterator - 具体迭代器

package com.linsir.designpattern.iterator;

import java.util.List;

public class ConcreteIterator implements Iterator {
    private List<Object> list;
    private int index = 0;

    public ConcreteIterator(List<Object> list) {
        this.list = list;
    }

    @Override
    public boolean hasNext() {
        return index < list.size();
    }

    @Override
    public Object next() {
        return list.get(index++);
    }
}

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2.4 ConcreteAggregate - 具体聚合

package com.linsir.designpattern.iterator;

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

public class ConcreteAggregate implements Aggregate {
    private List<Object> list = new ArrayList<>();

    public void add(Object obj) {
        list.add(obj);
    }

    public void remove(Object obj) {
        list.remove(obj);
    }

    @Override
    public Iterator createIterator() {
        return new ConcreteIterator(list);
    }
}

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三、使用示例

public class IteratorTest {
    public static void main(String[] args) {
        ConcreteAggregate aggregate = new ConcreteAggregate();
        aggregate.add("元素1");
        aggregate.add("元素2");
        aggregate.add("元素3");

        Iterator iterator = aggregate.createIterator();
        while (iterator.hasNext()) {
            System.out.println(iterator.next());
        }
    }
}

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四、Java内置迭代器

Java提供了内置的迭代器支持：

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

public class JavaIteratorTest {
    public static void main(String[] args) {
        List<String> list = new ArrayList<>();
        list.add("元素1");
        list.add("元素2");
        list.add("元素3");

        Iterator<String> iterator = list.iterator();
        while (iterator.hasNext()) {
            System.out.println(iterator.next());
        }
    }
}

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五、相关文档

• 设计模式概述