Copy List with Random Pointer

/**
 * Definition for singly-linked list with a random pointer.
 * class RandomListNode {
 *     int label;
 *     RandomListNode next, random;
 *     RandomListNode(int x) { this.label = x; }
 * };
 */
public class Solution {
    public RandomListNode copyRandomList(RandomListNode head) {
        HashMap<RandomListNode, RandomListNode> map = new HashMap<RandomListNode, RandomListNode>();
        RandomListNode fakehead = new RandomListNode(0);
        RandomListNode runner = head;
        RandomListNode newrunner = fakehead;
        
        while(runner!=null){
            RandomListNode node = null;
            if(map.containsKey(runner)){
                node = map.get(runner);
            }
            else{
                node = new RandomListNode(runner.label);
                map.put(runner, node);
            }
            newrunner.next = node;
            
            if(runner.random!=null){
                if(map.containsKey(runner.random)){
                    node = map.get(runner.random);
                }
                else{
                    node = new RandomListNode(runner.random.label);
                    map.put(runner.random, node);
                }
                newrunner.next.random = node;
            }
            newrunner = newrunner.next;
            runner = runner.next;
        }
        return fakehead.next;
    }
}