Need help inserting recursively

Question

I am writing a binary search tree, the tree nodes are basically string objects encapsulated by the TreeNode class. I have trouble writng the insert(Comparable item) which insert item to my BST. I have:
public void insert ( Comparable item ) throws BST_Exception{
        if(root == null)
            root = new TreeNode(item);
        else
            try{
                insertItem(root, item);
            }catch(BST_Exception e){
                //Ignore
duplicates                                                                                         
    }And a helper method:
private TreeNode insertItem (TreeNode t, Comparable item)
        throws BST_Exception{
        System.out.println("t = " + t + " item = " + item);
        //System.out.println("result = " + result);                                                                         
        if(t == null){
            t = new TreeNode(item);
            System.out.println("New Node: " + t);
        }else if(t.compareTo(new TreeNode(item)) < 0){
            t.setLeft(insertItem(t.getLeft(), item));
        }else if(t.compareTo(new TreeNode(item)) > 0){
            t.setRight(insertItem(t.getRight(), item));
        }else{
            throw new BST_Exception("Duplicate nodes! " + item);
        return t;
    }in this case item is of type String and TreeNode implements the Comparable interface just compare two string values.
I wrote a driver program executing the insertion methods above. But it didn't work out the way i want it to be:
t = 16 item = 13
t = null item = 13
New Node: 13
t = 16 item = 2
t = null item = 2
New Node: 2
t = 16 item = 11
t = 13 item = 11
t = null item = 11 //t should be 2
New Node: 11
t = 16 item = 15
t = 13 item = 15
t = null item = 15 //
New Node: 15
t = 16 item = 6
t = 2 item = 6
t = null item = 6 //
New Node: 6
t = 16 item = 10
t = 13 item = 10
t = 11 item = 10
t = null item = 10 //
New Node: 10
t = 16 item = 16
My input file is:
16
13
2
11
15
6
10
16
Any idea what i am doing wrong in insertItem()? Thanks!

Answer 1

Hello,
Try the following code and you will see that the result will be -1, which means that in Java 16 is "less" than 2.
public class TestString
     public static void main(String[] args)
          System.out.println("16".compareTo("2"));
}You need to compare your Strings as integers whenever you have integers.
Hope this helps