Can someone explain how to print at x depth in the main method? Binary search trees- java.

public class PrintDepth {
    private static int printdepth; // The depth to print all the elements.


    public static void main(String [] args) {
        MyTree T = new MyTree(); // Gets a Tree object.
        TreeNode root = T.getRoot(); // Gets the root of the tree.

        printdepth = 111; // sets the tree to depth 111. 


    }
}

public class TreeNode {
    public int key;
    public TreeNode left;
    public TreeNode right;

    public TreeNode(int _key, TreeNode l, TreeNode r) {
        key = _key;
        left = l;
        right = r;
    }
}