Combining recursive tree traversal subroutine and calling method?

Question

I wrote the following bit to take a TreeMap of string (words) and build into one long inorder traversed string (alphabetical order). Works fine-this isn't a do my homework problem =).
But I have two questions:
1. How, if any, is it possible to combine the recursive function and the one that calls it into one consolidated subroutine.
2. A little off topic, but can objects of different primitive types (like an int 2D array and a string) be stored with in each node? How can I specify which one is the "key" on traversal (the word), how can i access the other data (array)?
I'm bout to go over some documentation myself, I know I'll find something, but just wanted to know the general consensus on this type of execution. Thanks.
public String toString() {
        inOrderTreeResult = "Result of this tree is: ";
        inOrderTreeResult += (buildString(root));
        return inOrderTreeResult;       
    public String buildString(TreeNode node){
         if (node != null) {
              buildString( node.left );
              inOrderTreeResult += (node.item + "\n");
              buildString( node.right );
          return inOrderTreeResult;
     }

Answer 1

I'm not so sure I understand. Lemme show some code and explain. I have a simple treemap implementation to create an alphabetical index of words that appear in a text file. Currently the one data in each node is the String word. I want to be able to include the line number and number of iterations on each line that it appears. I could do it sloppily by putting all that information into one string and parsing it out later, or I thought maybe I could somehow add a 2D array (actually a vector for expandability) that I can access later when i print out the index.
Here's the constructor class of the Tree:
static class TreeNode {
          String item;     
          TreeNode left;   
          TreeNode right;  
          TreeNode(String str) {
                 item = str;
      }  On insertion, it traverses for the proper position on the tree and should add the string, if it exists, I should be able to access the vector and increment counters, add more line numbers, whatever.
Thanks.