writing a method for a seperate class file

Question

I have a .class file named UBT.class (which i do not have access to the source code). I need to retrieve data from the UBT.class file. I have access to methods such as .getRoot() & .getLeft() & .getRight() from the UBT class (Not using the methods from the TreeNode class).

I tried writing an inOrder traversal method using recursion like this but its giving me errors like below although i specifiy it to be UBT not TreeNode

Error: incompatible types: TreeNode cannot be converted to UBT

//From main method

     public static void inOrder(UBT root)
      {
        if(root.getRoot() != null)
        {
          inOrder(root.getRoot().getLeft());
          System.out.println(root.getRoot().getData() + " ");
          inOrder(root.getRoot().getRight());
        }
      }

class TreeNode
{
  private int data;
  private TreeNode left, right;

  public TreeNode(int data) {
    this.data = data;
    this.left = null;
    this.right = null;
  }

  public int getData() {
    return data;
  }

  public void setData(int newData){
    this.data = newData;
  }

  public TreeNode getLeft() {
    return left;
  }

  public TreeNode getRight() {
    return right;
  }

  public void setLeft(TreeNode left) {
    this.left = left;
  }

  public void setRight(TreeNode right) {
    this.right = right;
  }
}

class BST // Typical BST implementation

Answer 1

It looks like you want to split it up so your main recursion is on TreeNodes, not the UBT object.

  public static void inOrder(TreeNode node) {
    if(node != null)
    {
      inOrder(node.getLeft());
      System.out.println(node.getData() + " ");
      inOrder(node.getRight());
    }
  }

  public static void inOrder(UBT root) {
    if (root.getRoot() != null) {
      inOrder(root.getRoot());
    }
  }

Using this, you'd call inOrder with your UBT, then it would grab the root TreeNode and do recursion on that with the TreeNode version of inOrder.