We all know that java.util.Scanner is slow.

Here is a version in Scala that is idiomatic (you can do all the Collections API e.g. .take, .map, .filter etc) and supports line numbers too and is much faster than the Java Scanner:

import java.io._
import java.nio.file.{Files, Path}
import java.util.StringTokenizer

import scala.collection.JavaConversions._
import scala.io.Codec

/**
 * Scala implementation of a faster java.util.Scanner
 * See: http://codeforces.me/blog/entry/7018
 */
class Scanner(reader: LineNumberReader) extends Iterator[String] with AutoCloseable {
  def this(reader: BufferedReader) = this(new LineNumberReader(reader))
  def this(reader: Reader) = this(new BufferedReader(reader))
  def this(inputStream: InputStream)(implicit codec: Codec) = this(new InputStreamReader(inputStream, codec.charSet))
  def this(path: Path)(implicit codec: Codec) = this(Files.newBufferedReader(path, codec.charSet))
  def this(file: File)(implicit codec: Codec) = this(file.toPath)(codec)
  def this(str: String) = this(new StringReader(str))

  val lines: Iterator[String] = reader.lines().iterator()

  def tokens: Iterator[String] = for {
    line <- lines
    tokenizer = new StringTokenizer(line)
    _ <- Iterator.continually(tokenizer).takeWhile(_.hasMoreTokens)
  } yield tokenizer.nextToken()

  private[this] var current = tokens

  override def hasNext = current.hasNext
  @inline override def next() = current.next()

  /**
   * @return Unlike the Java scanner which returns till end of current line, this actually returns the next line
   */
  def nextLine(): String = {
    val line = reader.readLine()
    current = tokens   // reset
    line
  }
  def lineNumber: Int = reader.getLineNumber
  def nextString(): String = next()
  def nextBoolean(): Boolean = next().toBoolean
  def nextByte(radix: Int = 10): Byte = java.lang.Byte.parseByte(next(), radix)
  def nextShort(radix: Int = 10): Short = java.lang.Short.parseShort(next(), radix)
  def nextInt(radix: Int = 10): Int = java.lang.Integer.parseInt(next(), radix)
  def nextLong(radix: Int = 10): Long = java.lang.Long.parseLong(next(), radix)
  def nextBigInt(radix: Int = 10): BigInt = BigInt(next(), radix)
  def nextFloat(): Float = next().toFloat
  def nextDouble(): Double = next().toDouble
  def nextBigDecimal(): BigDecimal = BigDecimal(next())

  override def close() = reader.close()
}

Source: https://github.com/pathikrit/ScalaForces/blob/master/src/main/scala/Scanner.scala

Benchmarks: https://github.com/pathikrit/better-files/tree/master/benchmarks