2D List Iterator, Java

2D List Iterator

//'main' method must be in a class 'Rextester'.
//Compiler version 1.8.0_111

import java.util.*;
import java.lang.*;

class Rextester
{  
    public static void main(String args[])
    {
        List<Integer> list1 = new ArrayList<>(Arrays.asList(1, 2));
        List<Integer> list2 = new ArrayList<>(Arrays.asList(3));
        List<List<Integer>> vec2d = new ArrayList<>();
        vec2d.add(list1);
        vec2d.add(list2);
        //1,2
        //3
        ListOfListIterator<Integer> myIter = new ListOfListIterator<>(vec2d);
        System.out.println(myIter.hasNext());
        System.out.println(myIter.next());
        System.out.println(myIter.hasNext());
        myIter.remove();
        System.out.println(myIter.next());
        for (int i = 0; i < vec2d.size(); i++) {
            if (vec2d.get(i) == null) continue;
            for (int j = 0; j < vec2d.get(i).size(); j++) {
                System.out.println("List" + i + ":" + vec2d.get(i).get(j));
            }
            
        }
        System.out.println(myIter.hasNext());
        System.out.println(myIter.next());
    }
}

class ListOfListIterator<T> implements Iterator<T> {
    Iterator<List<T>> iter1;
    Iterator<T> iter2;
    
    public ListOfListIterator(List<List<T>> ListOfList) {
        iter1 = ListOfList.iterator();
        iter2 = null;
    }
    
    public boolean hasNext() {
        while ((iter2 == null || !iter2.hasNext()) && iter1.hasNext()) iter2 = iter1.next().iterator();
        return iter2 != null && iter2.hasNext();
    }
    
    public T next() {
        //if (iter2 == null) throw new NoSuchElementException();
        if (iter2 == null) throw new RuntimeException();
        return iter2.next();
    }
    
    public void remove() {
        //if (iter2 == null) throw new IllegalStateException();
        if (iter2 == null) throw new RuntimeException();
        iter2.remove();
    }
}


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