My first sloppy steps into Scala. Check corresponding blog post at http://spiechu.pl/2014/01/05/computing-file-hashes-using-scala

hashgenerator.scala

// Typical Java package declaration.
package pl.spiechu.hashutils

// Typical class imports. More than one in curly brackets.
// Java classes work just fine in Scala.
import java.io.{ File, FileInputStream }
import java.security.MessageDigest

/**
 * Singleton object. You cannot create an instance using 'new'.
 * Construct built-in into language.
 *
 * @author Dawid Spiechowicz ([email protected])
 */
object HashGenerator {

  // We're inside constructor body.

  /**
   * Input stream buffer size.
   *
   * Final val is constant expression.
   */
  final val BUFFER_SIZE = 8192

  /**
   * Hash algorithm type.
   */
  final val HASH_TYPE = "SHA-256"

  // Val ensures me that no one will reassign something to that.
  // Think about it as 'final' Java keyword.
  // Notice no empty bracket after name in array type.
  val buffer = new Array[Byte](BUFFER_SIZE)
  // You can leave off most of dots.
  val shaDigest = MessageDigest getInstance (HASH_TYPE)

  /**
   * You don't need to provide return type,
   * but you should because of public API clarity.
   */
  def getSha1HashUsingFuncChain(file: File): String = {
    // You can leave off parentheses in no arg functions.
    shaDigest reset

    val fis = new FileInputStream(file)

    // Infinite looping until read() result equals -1,
    // until that happens run foreach().
    Stream
      .continually(fis read (buffer))
      .takeWhile(_ != -1)
      .foreach(shaDigest update (buffer, 0, _))
    
    // Last expression in function is always returned.
    getHashString
  }

  /**
   * Works fine without return type provided.
   */
  def getSha1HashUsingMatcher(file: File) = {
    shaDigest reset

    val fis = new FileInputStream(file)

    // Define inner function that can be called recurrently.
    // Recursive method needs a return type. Think of 'Unit' as void.
    def readStream(): Unit = {
      // read() result intercepted by matcher.
      fis.read(buffer) match {
        case -1 => ()
        // Do digest update job and call recurrent.
        // Notice that readStream call is the last,
        // so compiler can perform tail recursion optimization.
        case num => shaDigest update (buffer, 0, num); readStream
      }
    }
    // Launch first iteration.
    readStream

    getHashString
  }

  /**
   * Default 'def' refers to 'public' access, You can narrow it.
   */
  protected def getHashString() = {
    val hexbuilder = new StringBuilder
    // Iterate over byte array and cut off everything beside one byte.
    // Eclipse complains about implicit conversion to 'byteArrayOps',
    // stay tuned for the next blog post at spiechu.pl explaining this.
    shaDigest.digest.foreach(bt => hexbuilder append (Integer toHexString (0xFF & bt)))
    hexbuilder toString
  }

}