問(wèn)題描述

我正在嘗試?yán)斫?Java Iterator 和 Iterable 接口

I am trying to understand Java Iterator and Iterable interfaces

我正在寫(xiě)這門(mén)課

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.

我應(yīng)該有:

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

}

或者我應(yīng)該把 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();
        }
    }   

哪個(gè)更好?

推薦答案

你應(yīng)該幾乎永遠(yuǎn)同時(shí)實(shí)現(xiàn) Iterable 和 Iterator班級(jí).他們做不同的事情.迭代器自然是有狀態(tài)的 - 當(dāng)您使用它進(jìn)行迭代時(shí)，它必須更新其對(duì)世界的看法.然而，一個(gè)可迭代對(duì)象只需要能夠創(chuàng)建新的迭代器.特別是，您可以讓多個(gè)迭代器同時(shí)處理同一個(gè)原始可迭代對(duì)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.

您當(dāng)前的方法非常好 - 我會(huì)更改實(shí)施的某些方面，但在職責(zé)分離方面很好.

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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