Print the hierarchy of a given class.

ClassHierarchy.scala

import scala.collection.SortedSet

sealed trait Tree[T] {
  val value: T
}
case class Leaf[T](value: T) extends Tree[T]
case class Node[T](value: T, children: SortedSet[Tree[T]]) extends Tree[T]

object ClassHierarchy {
  def main(args: Array[String]) =
    printTree(hierarchy(Class.forName(args(0))))

  def hierarchy(root: Class[_]): Tree[Class[_]] = {
    implicit val ordering = Ordering.by[Tree[Class[_]], String](_.value.getName)
    val superclassSet =
      if (root.getSuperclass == null)
        SortedSet.empty[Tree[Class[_]]]
      else
        SortedSet(hierarchy(root.getSuperclass))
    val interfaces = root.getInterfaces.toSet
    Node(root, superclassSet ++ interfaces.map(hierarchy))
  }

  def printTree(tree: Tree[_], level: Int = 0): Unit = {
    println("  " * level + tree.value)
    tree match {
      case Leaf(_) => Unit
      case Node(_, children) => children.foreach(child => printTree(child, level + 1))
    }
  }
}