How to print the hole Binary Search Tree with lines

Question

So, I have create Binary Search Tree and added the only method "add", which adds inputs to the tree. Here is my code for TreeNode:

  static class TreeNode{
    private int data;
    private TreeNode leftChild;
    private TreeNode rightChild;

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


    public void add(int data){
        if( data >= this.data){
            if(this.rightChild == null){
                this.rightChild = new TreeNode(data);
            }else{
                this.rightChild.add(data);
            }
        }else {
            if(this.leftChild == null){
                this.leftChild = new TreeNode(data);
            }else {
                this.leftChild.add(data);
            }
        }
    }

    public int getData(){
        return data;
    }
    public  void setLeftChild(TreeNode leftChild){
        this.leftChild = leftChild;
    }
    public  void setRightChild(TreeNode rightChild){
        this.rightChild = rightChild;
    }
    public TreeNode getLeftChild(){
        return leftChild;
    }
    public TreeNode getRightChild(){
        return rightChild;
    }}

Here is my Code for BinaryTree:

 static class BinaryTree{

  private TreeNode root;
  public void insert(int data){
        if(root == null){
            this.root = new TreeNode(data);
        }else{
            root.add(data);
        }
    }}

I want to make a method, which outputs the hole binary tree with lines for example: If the inputs are {102, 10, 180, 2, 100, 140, 1000}, I want to output the binary tree as a String with lines like this:

Any suggestions, how to implement a method which prints the binary Tree?