CODEWITHSUNDEEP
javaiterator
Jakob Nielsen
Jakob Nielsen

Reputation: 5198

Java - Trying to create an Iterator within an Iterator

The list over which I want to iterate, contains an Array.

What I am trying to do is to make it possible to create an Iterator within the Iterator, so that I am able to iterate over the array in every Listelement.

I tried it this way:

@Override
public Iterator<A> iterator() {
    return new MyListIterator();
}

private class MyListIterator implements Iterator<A>, Iterable<B>
{
    private Listelem current;

    private MyListIterator() 
    {
        this.current = head;
    }

    @Override
    public boolean hasNext() 
    {
        return this.current != null;
    }

    @Override
    public A next() 
    {
        A next       = this.current.getValue();
        this.current = this.current.getSuccessor();
        return next;
    }

    @Override
    public void remove() 
    {
        Listelem tmp = head;
        while( tmp.getSuccessor().getSuccessor() != this.current ) 
        {
            tmp = tmp.getSuccessor();
        }
        tmp.setSuccessor(this.current);
    }

    @Override
    public Iterator<B> iterator() {
        return new MyInnerListIterator();
    }

    private class MyInnerListIterator implements Iterator<B>
    {
        private int currentIndex = 0;
        private B[] array = current.getAssoc();
        @Override
        public boolean hasNext() {
            return currentIndex < array.length && array[currentIndex] != null;
        }

        @Override
        public B next() {
            return array[currentIndex++];
        }

        @Override
        public void remove() {

        }

    }
}

The problem is, when I am creating the first Iterator with iterator() the object does not contain the method iterator().

Can somebody explain to my why this is not working, and how to do it different?

Upvotes: 0

Views: 126

Answers (1)

Vitruvie
Vitruvie

Reputation: 2327

The problem is that iterator returns an Iterator, even though in this case it happens to also be a MyListIterator. Class Iterator does not have an iterator() function. You need to have iterator() return a MyListIterator, so that you can use methods not in the Iterator interface. It is likely simpler however, to simply use a for:in loop:

List<Object[]> list = ....
for (Iterator<Object[]> it = list.iterator(); it.hasNext();) {
    Object[] arr = it.next();
    for (Object o : arr) {
        ...
    }
}

And if you don't need to remove elements from the list, then you can replace the iterator use with another for:in

Upvotes: 1

Related Questions