import java.io.File
object Mp42m4a {
def main (args: Array[String]) {
if (args.length == 1) traverse(args(0))
}
private def traverse(path: String): Unit = {
val target = new File(path)
if (!target.exists()) { println(path + " not exists"); return None }
if (target.isFile()) changeName(target)
else target.list().foreach(x => traverse(path + "\\" + x))
}
private def changeName(file: File): Unit = {
if (file.getName().takeRight(4).toLowerCase() != ".mp4") return None
val fullname = new StringBuilder(file.getAbsolutePath())
val replaced = fullname.replace(fullname.length - 4, fullname.length, ".m4a")
file.renameTo(new File(replaced.toString))
}
}