How to use an arrayList to implement next() in Iterator

Question

I am attempting to implement an iterator class for my binary search tree. (to be more precise, it is a KD-Tree, but I don't think that will change things much). I want the iterator to follow an in-order traversal of the tree. I have an arrayList which contains the leaf nodes in this "in-order" order, and I would like the iterator to iterate through these leaf nodes in this order. How can I use this arrayList to implement next() method?

I have tried creating an int field called index in the Iterator class. Then my next() method would increment the index by 1 and return arrayList.get(index). However, this didn't seem to work.

Using the arrayList to implement next() isn't necessary, but it seemed like the easiest way. If there is a way to do this with the arrayList, that would be preferred. Is this even possible? If not, any advice whatsoever would be welcome! Thanks

You have an ArrayList holding all the nodes? This is strange if the data structure is supposed to be a binary search tree. Could you edit the question to include more details about what's in this ArrayList, and in what order? — kaya3
– kaya3, Commented Nov 15, 2019 at 3:46
The ArrayList contains only the leaf nodes, as in this case, the leaf nodes contain all the important data. Then I would like my iterator to be able to iterate through these leaf nodes. — jonan
– jonan, Commented Nov 15, 2019 at 3:52
What does it mean to do an in-order traversal over just the leaf nodes? If only the leaf nodes are processed, then either pre-order, in-order or post-order would process the leaf nodes in the same order. Does the ArrayList happen to contain the nodes in the right order already, by any chance? — kaya3
– kaya3, Commented Nov 15, 2019 at 3:56
Yes, that was why I made the ArrayList. The arrayList contains the elements in the order in which I wish to iterate them in. So regardless of "in-order", I simply want my next() method to follow the order of my ArrayList — jonan
– jonan, Commented Nov 15, 2019 at 4:35
So you can just write arrayList.iterator() to get an iterator, then. — kaya3
– kaya3, Commented Nov 15, 2019 at 4:41

sovannarith cheav · Accepted Answer · 2019-11-15 03:49:29Z

1

You can create an iterator for the list using iterator() method.


        // Create and populate the list 
        ArrayList<String> list = new ArrayList<>(); 

        list.add("Hello"); 
        list.add("World");

        // Displaying the list 
        System.out.println("The list is: "+ list); 

        // Create an iterator for the list 
        // using iterator() method 
        Iterator<String> iter = list.iterator(); 

        while (iter.hasNext()) { 
            System.out.print(iter.next() + " "); 
        }

answered Nov 15, 2019 at 3:49

sovannarith cheav

7931 gold badge6 silver badges19 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

How to use an arrayList to implement next() in Iterator

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related