def selectEntities[A <: Entity](box: AxisAlignedBB, clazz: Class[A])(implicit precondition: PartialFunction[A, Boolean]): List[A] = {
  import scala.collection.JavaConversions._
  world.getEntitiesWithinAABB(clazz, box).map(_.asInstanceOf[A]).filter(e => if (precondition != null) precondition.applyOrElse(e, (e1: A) => false) else true).toList
}