LeetCode Binary Search Tree Iterator

BSTIterator.java

import java.util.*;

public class BSTIterator {

    /**
     * Definition for binary tree
     * public class TreeNode {
     *     int val;
     *     TreeNode left;
     *     TreeNode right;
     *     TreeNode(int x) { val = x; }
     * }
     */

    Stack<Integer> nums = new Stack<>();
    
    public BSTIterator(TreeNode root) {
        Stack<TreeNode> nodes = new Stack<>();
        TreeNode p = root;
        while(!nodes.isEmpty() || p != null){
            if(p != null){
                nodes.push(p);
                p = p.right;
            }else{
                TreeNode n = nodes.pop();
                nums.push(n.val);
                p = n.left;
            }
        }
    }

    /** @return whether we have a next smallest number */
    public boolean hasNext() {
        if(nums.size() > 0){
            return true;
        }else{
            return false;
        }
    }

    /** @return the next smallest number */
    public int next() {
        return nums.pop();
    }

    /**
     * Your BSTIterator will be called like this:
     * BSTIterator i = new BSTIterator(root);
     * while (i.hasNext()) v[f()] = i.next();
     */
    
}