在同一个类中实现 Java Iterator 和 Iterable?

2022-01-10 00:00:00 iterable iterator java

我正在尝试理解 Java Iterator 和 Iterable 接口

I am trying to understand Java Iterator and Iterable interfaces

我正在写这门课

class MyClass implements Iterable<String> {
    public String[] a = null;
    public MyClass(String[] arr) {
        a = arr;    
    }

    public MyClassIterator iterator() {
        return new MyClassIterator(this);
    }

    public class MyClassIterator implements Iterator<String> {
        private MyClass myclass = null;
        private int count = 0;
        public MyClassIterator(MyClass m) {
            myclass = m;    
        }

        public boolean hasNext() {
            return count < myclass.a.length;
        }
        public String next() {
            int t = count;
            count++;
            return myclass.a[t];
        }

        public void remove() {
            throw new UnsupportedOperationException();
        }
    }   
}

它似乎正在工作.

我应该有:

Myclass implements Iterable<Stirng>, Iterator<String> {

}

或者我应该把 MyClassIterator 放在 MyClass 之外

Or I should put MyClassIterator outside MyClass as

class MyClass implements Iterable<String> {
    public String[] a = null;
    public MyClass(String[] arr) {
        a = arr;    
    }
    public MyClassIterator iterator() {
        return new MyClassIterator(this);
    }
}


    public class MyClassIterator implements Iterator<String> {
        private MyClass myclass = null;
        private int count = 0;
        public MyClassIterator(MyClass m) {
            myclass = m;    
        }

        public boolean hasNext() {
            return count < myclass.a.length;
        }
        public String next() {
            int t = count;
            count++;
            return myclass.a[t];
        }

        public void remove() {
            throw new UnsupportedOperationException();
        }
    }

哪个更好?

推荐答案

你应该几乎永远同时实现 Iterable 和 Iterator班级.他们做不同的事情.迭代器自然是有状态的 - 当您使用它进行迭代时，它必须更新其对世界的看法.然而，一个可迭代对象只需要能够创建新的迭代器.特别是，您可以让多个迭代器同时处理同一个原始可迭代对象.

You should almost never implement both Iterable and Iterator in the same class. They do different things. An iterator is naturally stateful - as you iterate using it, it has to update its view of the world. An iterable, however, only needs to be able to create new iterators. In particular, you could have several iterators working over the same original iterable at the same time.

您当前的方法非常好 - 我会更改实施的某些方面，但在职责分离方面很好.

Your current approach is pretty much okay - there are aspects of the implementation I'd change, but it's fine in terms of the separation of responsibilities.

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