Read a 16-byte file and print as a UUID

fileToUuid.kt

import java.io.File
import java.util.UUID
import java.nio.ByteBuffer

fun main(vararg args: String) {
    val filename = args.firstOrNull()
    if (filename == null) {
        System.err.println("Usage: kotlin UuidKt <filename>")
        System.exit(1)
    } 
    val file = File(filename)
    if (!file.isFile()) {
        System.err.println("File does not exist")
        System.exit(1)
    }
    val bytes = ByteBuffer.wrap(file.readBytes())
    val uuid = UUID(bytes.getLong(), bytes.getLong())
    println(uuid.toString())
}