Java设计模式之迭代器模式详解

// 迭代器接口
public interface Iterator<T> {
    boolean hasNext();
    T next();
}
// 具体迭代器
public class ConcreteIterator<T> implements Iterator<T> {
    private List<T> elements;
    private int position = 0;
    public ConcreteIterator(List<T> elements) {
        this.elements = elements;
    }
    @Override
    public boolean hasNext() {
        return position < elements.size();
    }
    @Override
    public T next() {
        if (this.hasNext()) {
            return elements.get(position++);
        }
        return null;
    }
}
// 聚合接口
public interface Aggregate<T> {
    Iterator<T> createIterator();
}
// 具体聚合
public class ConcreteAggregate<T> implements Aggregate<T> {
    private List<T> elements;
    public ConcreteAggregate(List<T> elements) {
        this.elements = elements;
    }
    @Override
    public Iterator<T> createIterator() {
        return new ConcreteIterator<>(elements);
    }
}

// 创建具体聚合对象
Aggregate<String> aggregate = new ConcreteAggregate<>(Arrays.asList("Java", "Design", "Pattern"));
// 获取迭代器
Iterator<String> iterator = aggregate.createIterator();
// 遍历集合
while (iterator.hasNext()) {
    String element = iterator.next();
    System.out.println(element);
}