Scala example source code file (StdIn.scala)

This example Scala source code file (StdIn.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Scala source code examples by using tags.

All credit for the original source code belongs to scala-lang.org; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Scala tags/keywords

any, array, boolean, byte, console, double, int, list, stdin, string

The StdIn.scala Scala example source code

package scala
package io

import java.text.MessageFormat

/** private[scala] because this is not functionality we should be providing
 *  in the standard library, at least not in this idiosyncractic form.
 *  Factored into trait because it is better code structure regardless.
 */
private[scala] trait StdIn {
  import scala.Console._

  /** Read a full line from the default input.  Returns `null` if the end of the
   * input stream has been reached.
   *
   * @return the string read from the terminal or null if the end of stream was reached.
   */
  def readLine(): String = in.readLine()

  /** Print and flush formatted text to the default output, and read a full line from the default input.
   *  Returns `null` if the end of the input stream has been reached.
   *
   *  @param text the format of the text to print out, as in `printf`.
   *  @param args the parameters used to instantiate the format, as in `printf`.
   *  @return the string read from the default input
   */
  def readLine(text: String, args: Any*): String = {
    printf(text, args: _*)
    out.flush()
    readLine()
  }

  /** Reads a boolean value from an entire line of the default input.
   *  Has a fairly liberal interpretation of the input.
   *
   *  @return the boolean value read, or false if it couldn't be converted to a boolean
   *  @throws java.io.EOFException if the end of the input stream has been reached.
   */
  def readBoolean(): Boolean = {
    val s = readLine()
    if (s == null)
      throw new java.io.EOFException("Console has reached end of input")
    else
      s.toLowerCase() match {
        case "true" => true
        case "t" => true
        case "yes" => true
        case "y" => true
        case _ => false
      }
  }

  /** Reads a byte value from an entire line of the default input.
   *
   *  @return the Byte that was read
   *  @throws java.io.EOFException if the end of the
   *  input stream has been reached.
   *  @throws java.lang.NumberFormatException if the value couldn't be converted to a Byte
   */
  def readByte(): Byte = {
    val s = readLine()
    if (s == null)
      throw new java.io.EOFException("Console has reached end of input")
    else
      s.toByte
  }

  /** Reads a short value from an entire line of the default input.
   *
   *  @return the short that was read
   *  @throws java.io.EOFException if the end of the
   *  input stream has been reached.
   *  @throws java.lang.NumberFormatException if the value couldn't be converted to a Short
   */
  def readShort(): Short = {
    val s = readLine()
    if (s == null)
      throw new java.io.EOFException("Console has reached end of input")
    else
      s.toShort
  }

  /** Reads a char value from an entire line of the default input.
   *
   *  @return the Char that was read
   *  @throws java.io.EOFException if the end of the
   *  input stream has been reached.
   *  @throws java.lang.StringIndexOutOfBoundsException if the line read from default input was empty
   */
  def readChar(): Char = {
    val s = readLine()
    if (s == null)
      throw new java.io.EOFException("Console has reached end of input")
    else
      s charAt 0
  }

  /** Reads an int value from an entire line of the default input.
   *
   *  @return the Int that was read
   *  @throws java.io.EOFException if the end of the
   *  input stream has been reached.
   *  @throws java.lang.NumberFormatException if the value couldn't be converted to an Int
   */
  def readInt(): Int = {
    val s = readLine()
    if (s == null)
      throw new java.io.EOFException("Console has reached end of input")
    else
      s.toInt
  }

  /** Reads an long value from an entire line of the default input.
   *
   *  @return the Long that was read
   *  @throws java.io.EOFException if the end of the
   *  input stream has been reached.
   *  @throws java.lang.NumberFormatException if the value couldn't be converted to a Long
   */
  def readLong(): Long = {
    val s = readLine()
    if (s == null)
      throw new java.io.EOFException("Console has reached end of input")
    else
      s.toLong
  }

  /** Reads a float value from an entire line of the default input.
   *  @return the Float that was read.
   *  @throws java.io.EOFException if the end of the
   *  input stream has been reached.
   *  @throws java.lang.NumberFormatException if the value couldn't be converted to a Float
   *
   */
  def readFloat(): Float = {
    val s = readLine()
    if (s == null)
      throw new java.io.EOFException("Console has reached end of input")
    else
      s.toFloat
  }

  /** Reads a double value from an entire line of the default input.
   *
   *  @return the Double that was read.
   *  @throws java.io.EOFException if the end of the
   *  input stream has been reached.
   *  @throws java.lang.NumberFormatException if the value couldn't be converted to a Float
   */
  def readDouble(): Double = {
    val s = readLine()
    if (s == null)
      throw new java.io.EOFException("Console has reached end of input")
    else
      s.toDouble
  }

  /** Reads in some structured input (from the default input), specified by
   *  a format specifier. See class `java.text.MessageFormat` for details of
   *  the format specification.
   *
   *  @param format the format of the input.
   *  @return a list of all extracted values.
   *  @throws java.io.EOFException if the end of the input stream has been
   *          reached.
   */
  def readf(format: String): List[Any] = {
    val s = readLine()
    if (s == null)
      throw new java.io.EOFException("Console has reached end of input")
    else
      textComponents(new MessageFormat(format).parse(s))
  }

  /** Reads in some structured input (from the default input), specified by
   *  a format specifier, returning only the first value extracted, according
   *  to the format specification.
   *
   *  @param format format string, as accepted by `readf`.
   *  @return The first value that was extracted from the input
   */
  def readf1(format: String): Any = readf(format).head

  /** Reads in some structured input (from the default input), specified
   *  by a format specifier, returning only the first two values extracted,
   *  according to the format specification.
   *
   *  @param format format string, as accepted by `readf`.
   *  @return A [[scala.Tuple2]] containing the first two values extracted
   */
  def readf2(format: String): (Any, Any) = {
    val res = readf(format)
    (res.head, res.tail.head)
  }

  /** Reads in some structured input (from the default input), specified
   *  by a format specifier, returning only the first three values extracted,
   *  according to the format specification.
   *
   *  @param format format string, as accepted by `readf`.
   *  @return A [[scala.Tuple3]] containing the first three values extracted
   */
  def readf3(format: String): (Any, Any, Any) = {
    val res = readf(format)
    (res.head, res.tail.head, res.tail.tail.head)
  }

  private def textComponents(a: Array[AnyRef]): List[Any] = {
    var i: Int = a.length - 1
    var res: List[Any] = Nil
    while (i >= 0) {
      res = (a(i) match {
        case x: java.lang.Boolean   => x.booleanValue()
        case x: java.lang.Byte      => x.byteValue()
        case x: java.lang.Short     => x.shortValue()
        case x: java.lang.Character => x.charValue()
        case x: java.lang.Integer   => x.intValue()
        case x: java.lang.Long      => x.longValue()
        case x: java.lang.Float     => x.floatValue()
        case x: java.lang.Double    => x.doubleValue()
        case x => x
      }) :: res
      i -= 1
    }
    res
  }
}

object StdIn extends StdIn