Program to delete a tree

Source:
problem link

Code:
public class DeleteTree {
    Node root;
   
    void deleteTree(Node node){
        if(node == null)
            return;
        deleteTree(node.left);
        deleteTree(node.right);
        System.out.println("node to delete "+node.data);
        node = null;
    }
   
    void deleteTreeRef(Node root)
    {
        deleteTree(root);
        root=null;
    }
   
    public static void main(String[] args){
        DeleteTree tree = new DeleteTree();
       
        tree.root = new Node(1);
        tree.root.left = new Node(2);
        tree.root.right = new Node(3);
       
        tree.deleteTreeRef(tree.root);
       
    }

}

Output:

node to delete 2
node to delete 3
node to delete 1

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