integer Binary Tree implementation (only add)

public class Main{

    public static void main(String[] args) {
        BinaryTree bt = new BinaryTree();
        bt.add(4);
        bt.add(1);
        bt.add(5);
        bt.add(3);
        bt.add(3);
    }

}

class BinaryTree{

    private class Node{
        int data;
        Node left;
        Node right;

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

    Node root;
    int size;

    public BinaryTree(){
        root = null;
        size = 0;
    }

    public BinaryTree(int data){
        root = new Node(data);
        size = 1;
    }

    public void add(int data){
        if(size == 0){
            root = new Node(data);
            size++;
        } else {
            Node current = root;
            boolean found = false;
            while(!found){
                if(current.data >= data){
                    if(current.left != null){
                        current = current.left;
                    } else {
                        found = true;
                    }
                } else if(current.data < data){
                    if(current.right != null){
                        current = current.right;
                    } else{
                        found = true;
                    }
                }
            }

            if(current.data >= data){
                current.left = new Node(data);
            } else {
                current.right = new Node(data);
            }
            size++;
        }
    }


}