import java.io.File

def listFiles(path: String): Unit = {
  val directory = new File(path)
  val files = directory.listFiles()
  
  if (files != null) {
    for (file <- files) {
      if (file.isDirectory) {
        listFiles(file.getAbsolutePath)
      } else {
        println(file.getAbsolutePath)
      }
    }
  }
}

val path = "/path/to/directory"
listFiles(path)