二十三种设计模式全面解析-解密迭代器模式：探索遍历之道

// 迭代器接口
interface Iterator<T> {
    boolean hasNext();
    T next();
}
// 抽象集合类
interface List<T> {
    Iterator<T> createIterator();
    int size();
    T get(int index);
}
// 具体迭代器
class ArrayListIterator<T> implements Iterator<T> {
    private List<T> list;
    private int index;
    public ArrayListIterator(List<T> list) {
        this.list = list;
        this.index = 0;
    }
    public boolean hasNext() {
        return index < list.size();
    }
    public T next() {
        if (hasNext()) {
            T element = list.get(index);
            index++;
            return element;
        }
        return null;
    }
}
// 具体集合类
class ArrayList<T> implements List<T> {
    private T[] elements;
    private int size;
    public ArrayList() {
        this.elements = (T[]) new Object[10];
        this.size = 0;
    }
    public void add(T element) {
        elements[size] = element;
        size++;
    }
    public T get(int index) {
        if (index >= 0 && index < size) {
            return elements[index];
        }
        return null;
    }
    public int size() {
        return size;
    }
    public Iterator<T> createIterator() {
        return new ArrayListIterator<>(this);
    }
}
// 客户端代码
public class IteratorPatternDemo {
    public static void main(String[] args) {
        ArrayList<String> names = new ArrayList<>();
        names.add("Alice");
        names.add("Bob");
        names.add("Charlie");
        Iterator<String> iterator = names.createIterator();
        while (iterator.hasNext()) {
            String name = iterator.next();
            System.out.println(name);
        }
    }
}