build.sbt

libraryDependencies ++= Seq("org.clapper" %% "classutil" % "1.0.5")

SearchSubClassesInRuntimeClassLoader.scala

import java.io.File
import org.clapper.classutil.ClassFinder

Object App extends App {
  val classloader = Thread.currentThread.getContextClassLoader // some classloader
  val classpath = classloader.getResource(".").toURI
  val finder = ClassFinder(Seq(File(classpath)))
  val classes = finder.getClasses.toIterator
  val subClasses = ClassFinder.concreteSubclasses("com.foo.bar.ParentInterface", classes)
  subClasses.foreach(println)
}