Return Deepest Node in Binary Tree

ReturnDeepestNode.java

//Return deepest, rightmost node in a tree
//Implementation: use DFS

import java.util.Queue;
import java.util.LinkedList;

public class Main
{
  public static void main(String[] args)
  {
    BinaryTree tree = new BinaryTree();
    
    tree.add(5);
    tree.add(4);
    tree.add(6);
    tree.add(3);
    tree.add(7);
    tree.add(2);
    tree.add(8);
    tree.add(1);
    tree.add(11);
    
    TreeNode node = tree.returnLastNode();
    
    System.out.println("last node: " + node.data);
    
    
  }
}
 
public class TreeNode
{
  int data;
  TreeNode left;
  TreeNode right;
  
  public TreeNode(int d){
  	data = d;
    left = null;
    right = null;
  }
  
}
 
public class IntWrapper{
 int value = 0; 
}
 
public class BinaryTree
{
  TreeNode root;
  
  public BinaryTree(){
  	root = null;
  }
  
  public boolean add(int newData){
    if (root == null){
      root = new TreeNode(newData);
      return true;
    }
    else{
      TreeNode curr = root;
      while (true){
        if (curr.data == newData){
          return false;
        }
        else if (curr.data > newData){
          if (curr.left == null){
            curr.left = new TreeNode(newData);
            return true;
          }
          else{
            curr = curr.left;
          }
          
          
        }
        else{
          if (curr.right == null){
            curr.right = new TreeNode(newData);
            return true;
          }
          else{
            curr = curr.right;
          }
        }
      }
    }
    
  }
  
  
  public TreeNode returnLastNode(){
    if (root == null) return null;
    if (root.left == null && root.right == null) return root;
    
    Queue<TreeNode> queue = new LinkedList<TreeNode>();
    
    queue.add(root);
  
    TreeNode lastNode = null;
    while (!queue.isEmpty()){
      lastNode = queue.remove();
      if (lastNode.left != null)
      	queue.add(lastNode.left);
      if (lastNode.right != null)
      	queue.add(lastNode.right);
    
    }
    return lastNode;
    
  }
  
   
}