Check if a Binary Tree contains duplicate subtrees of size 2 or more

Node.java

/**
 *
 * @author Sahil Kadam
 */
import java.util.*;
public class Node{
    String name;
    Node left,right;
    //ArrayList<String> subTree = new ArrayList<String>();
    Node(String name){
        this.name = name;
        this.left = null;
        this.right = null;
    }
    public void setLeft(Node left){
        this.left = left;
    }
    public void setRight(Node right){
        this.right = right;
    }
    public void display(){
        System.out.println(name);
    }
    
    public String getName(){
        return this.name;
    }

     public static void main(String []args){
        Node A = new Node("A");
        Node B = new Node("B");
        Node C = new Node("C");
        Node D = new Node("D");
        Node E = new Node("E");
        Node B1 = new Node("B");
        Node D1 = new Node("D");
        Node E1 = new Node("E");
        Node F = new Node("F");
        A.setLeft(B);
        A.setRight(C);
        B.setLeft(D);
        B.setRight(E);
        C.setRight(B1);
        B1.setLeft(D1);
        B1.setRight(E1);
        //A.display();
        //A.left.left.display();
        findDuplicate(A);
     }
     
     public static void findDuplicate(Node root){
         HashSet subTreeList = getSubTree(root);
         if(subTreeList.contains("Duplicate"))
             System.out.println("Yes");
         else
             System.out.println("No");
     }
     
     public static HashSet getSubTree(Node root){
         HashSet<String> subTree = new HashSet<String>();
         if(root == null)
             return subTree;
         if(root.left == null && root.right == null){
             subTree.add(root.getName());
             return subTree;
         }
         HashSet<String> leftTree = getSubTree(root.left);
         String currentTree = "";
         int leftTreeSize = 0;
         String leftChild = "";
         Iterator iteratorLeft = leftTree.iterator(); 
         while(iteratorLeft.hasNext()){
             String tmpLeft = iteratorLeft.next().toString();
             if(tmpLeft.length() > leftTreeSize){
                 leftTreeSize = tmpLeft.length();
                 leftChild = tmpLeft;
             }
             if(subTree.contains(tmpLeft) && tmpLeft.length() > 1)
                 subTree.add("Duplicate");
             else
                 subTree.add(tmpLeft);
         }
         currentTree += leftChild;
         currentTree += root.getName();
         HashSet<String> rightTree = getSubTree(root.right);
         int rightTreeSize = 0;
         String rightChild = "";
         Iterator iteratorRight = rightTree.iterator(); 
         while(iteratorRight.hasNext()){
             String tmpRight = iteratorRight.next().toString();
             if(tmpRight.length() > rightTreeSize){
                 rightTreeSize = tmpRight.length();
                 rightChild = tmpRight;
             }
             if(subTree.contains(tmpRight) && tmpRight.length() > 1)
                 subTree.add("Duplicate");
             else
                 subTree.add(tmpRight);
         }
         currentTree += rightChild;
         if(subTree.contains(currentTree) && currentTree.length() > 1)
            subTree.add("Duplicate");
         else
             subTree.add(currentTree);
         return subTree;
     }
}