leetcode341. Flatten Nested List Iterator

Given a nested list of integers, implement an iterator to flatten it.

Each element is either an integer, or a list -- whose elements may also be integers or other lists.

Example 1:
Given the list [[1,1],2,[1,1]],

By calling next repeatedly until hasNext returns false, the order of elements returned by next should be: [1,1,2,1,1].

Example 2:
Given the list [1,[4,[6]]],
By calling next repeatedly until hasNext returns false, the order of elements returned by next should be: [1,4,6].

    public class FlattenNestedListIterator_341 implements Iterator<Integer>{

        private List<NestedInteger> nestedList;
        private Iterator<Integer> iterator;
        private int next;
        private int index;
        public FlattenNestedListIterator_341(List<NestedInteger> nestedList){
            this.nestedList = nestedList;
        }
        
         @Override
        public Integer next() {
             return next;
        }

        @Override
        public boolean hasNext() {
            if(iterator != null && iterator.hasNext()){
                this.next = iterator.next();
                return true;
            }
            
            if(index>=nestedList.size()){
                return false;
            }
            
            NestedInteger n = nestedList.get(index++);
            if(n.isInteger()){
                next = n.getInteger();
            }else{
                iterator = new FlattenNestedListIterator_341(n.getList());
                if(iterator.hasNext()){
                    next = iterator.next();
                }else{
                    return hasNext();
                }
            }
            return true;
        }
}