Javaでバイナリツリーを階層形式で出力するにはどうすればよいですか?

public class TreeNode<A extends Comparable> {
    TreeNode<A> left, right;
    A data;
}

public String toString() {
    StringBuilder builder = new StringBuilder();
    print(builder, "", "");
    return builder.toString();
}

private void print(StringBuilder builder, String prefix, String childrenPrefix) {
    builder.append(prefix).append(data).append('\n');
    if (left != null) {
        left.print(builder, childrenPrefix + "├── ", childrenPrefix + "│   ");
    }
    if (right != null) {
        right.print(builder, childrenPrefix + "└── ", childrenPrefix + "    ");
    }
}

TreeNode<Integer> root = new TreeNode<>(4);
root.left = new TreeNode<>(2);
root.right = new TreeNode<>(5);
System.out.println(root.toString());

4
├── 2
└── 5