设计模式之迭代器模式

迭代器模式

迭代器模式结构图：

示例代码：

// 抽象迭代器
public interface Iterator <E>{

    boolean hasNext();

    E next();
}

// 具体迭代器
public class ConcreteIterator<E> implements Iterator<E>{

    private List<E> list;
    private int index = 0;

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

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

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

// 抽象容器
public interface Aggregate<E> {

    boolean add(E element);

    boolean remove(E element);

    Iterator<E> iterator();
}

// 具体容器
public class ConcreteAggregate<E> implements Aggregate<E>{

    private List<E> list = new ArrayList<>();

    @Override
    public boolean add(E element) {
        return list.add(element);
    }

    @Override
    public boolean remove(E element) {
        return list.remove(element);
    }

    @Override
    public Iterator<E> iterator() {
        return new ConcreteIterator<>(list);
    }
}

// 测试类
public class IteratorTest {

    public static void main(String[] args) {
        ConcreteAggregate<String> aggregate = new ConcreteAggregate<>();
        aggregate.add("A");
        aggregate.add("B");
        aggregate.add("C");
        aggregate.add("D");
        Iterator<String> iterator = aggregate.iterator();
        while (iterator.hasNext()){
            System.out.println(iterator.next());
        }
    }
}