Design Pattern for Iterator with Pagination with Java

Question

I'm attempting to make service calls to an API that returns back results in a paged format and want suggestions on the design pattern for the iterator for this.

What I have till now is something like this

public class CustomIterator implements Iterator<Type> {

 private List<Result> results;
 private Service service;

 private int index;
 private int paginatedResultSize;
 private int totalResultsSize;

 public CustomIterator(Service service) {
  this.service = service;
  this.index = 0;
  this.results = getResults(index);
  this.totalResultsSize = this.results.totalResultsSize();
 }

 @Override
 public boolean hasNext() {
   if (index < totalResultsSize)
    return true;
   return false;
 }

 @Override
 public Type next() {

  if(index == paginatedResultSize) {
   getResults(index);
  }

  return results[index++];

 }

 private List<Result> getResults(index) throws Exception {
  this.results = service.makeServiceCall(index);
  this.paginatedResultSize = this.results.size();
  return this.results;
 }

}

Now, I understand that the purpose of the iterator is normally to just iterate, but I also want to encapsulate the whole pagination into a separate area so my client class can just call .next() on the class and get all values without having to know about the internal pagination details. Is there a clean pattern to getting this done?

With this the first issue I ran into was that the service call was throwing a checked exception and next() obviously does not.

Some options I noticed on the internet were to have this throw a RunTimeException which I'd rather only do as a last resort since I like checked exceptions for service calls. My gut feeling is that the service call should be done in a separate layer completely, but I'm not sure how the iterator will work with that pagination there. Any suggestions/links appreciated.

Answer 1

This is a perfectly acceptable approach.

How you handle exceptions is up to you. If the exception is something like AttemptToReadBeyondLimit then just return false from hasNext. If it is something like CommunicationsException then by all means throw a RuntimeException.

You shouldnt add extra layers unnecessarily.