Packages

o

scala

Console

object Console extends AnsiColor

Implements functionality for printing Scala values on the terminal. For reading values use StdIn. Also defines constants for marking up text on ANSI terminals.

Console Output

Use the print methods to output text.

scala> Console.printf(
  "Today the outside temperature is a balmy %.1f°C. %<.1f°C beats the previous record of %.1f°C.\n",
  -137.0,
  -135.05)
Today the outside temperature is a balmy -137.0°C. -137.0°C beats the previous record of -135.1°C.

ANSI escape codes

Use the ANSI escape codes for colorizing console output either to STDOUT or STDERR.

import Console.{GREEN, RED, RESET, YELLOW_B, UNDERLINED}

object PrimeTest {

  def isPrime(): Unit = {

    val candidate = io.StdIn.readInt().ensuring(_ > 1)

    val prime = (2 to candidate - 1).forall(candidate % _ != 0)

    if (prime)
      Console.println(s"${RESET}${GREEN}yes${RESET}")
    else
      Console.err.println(s"${RESET}${YELLOW_B}${RED}${UNDERLINED}NO!${RESET}")
  }

  def main(args: Array[String]): Unit = isPrime()

}

$ scala PrimeTest
1234567891
yes
$ scala PrimeTest
56474
NO!

IO redefinition

Use IO redefinition to temporarily swap in a different set of input and/or output streams. In this example the stream based method above is wrapped into a function.

import java.io.{ByteArrayOutputStream, StringReader}

object FunctionalPrimeTest {

  def isPrime(candidate: Int): Boolean = {

    val input = new StringReader(s"$candidate\n")
    val outCapture = new ByteArrayOutputStream
    val errCapture = new ByteArrayOutputStream

    Console.withIn(input) {
      Console.withOut(outCapture) {
        Console.withErr(errCapture) {
          PrimeTest.isPrime()
        }
      }
    }

    if (outCapture.toByteArray.nonEmpty) // "yes"
      true
    else if (errCapture.toByteArray.nonEmpty) // "NO!"
      false
    else throw new IllegalArgumentException(candidate.toString)
  }

  def main(args: Array[String]): Unit = {
    val primes = (2 to 50) filter (isPrime)
    println(s"First primes: $primes")
  }

}

$ scala FunctionalPrimeTest
First primes: Vector(2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47)

Source
Console.scala
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  1. Console
  2. AnsiColor
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Value Members

  1. final def !=(arg0: Any): Boolean

    Test two objects for inequality.

    Test two objects for inequality.

    returns

    true if !(this == that), false otherwise.

    Definition Classes
    AnyRef → Any
  2. final def ##: Int

    Equivalent to x.hashCode except for boxed numeric types and null.

    Equivalent to x.hashCode except for boxed numeric types and null. For numerics, it returns a hash value which is consistent with value equality: if two value type instances compare as true, then ## will produce the same hash value for each of them. For null returns a hashcode where null.hashCode throws a NullPointerException.

    returns

    a hash value consistent with ==

    Definition Classes
    AnyRef → Any
  3. final def ==(arg0: Any): Boolean

    The expression x == that is equivalent to if (x eq null) that eq null else x.equals(that).

    The expression x == that is equivalent to if (x eq null) that eq null else x.equals(that).

    returns

    true if the receiver object is equivalent to the argument; false otherwise.

    Definition Classes
    AnyRef → Any
  4. final val BLACK: String("\u001B[30m")

    Foreground color for ANSI black

    Foreground color for ANSI black

    Definition Classes
    AnsiColor
  5. final val BLACK_B: String("\u001B[40m")

    Background color for ANSI black

    Background color for ANSI black

    Definition Classes
    AnsiColor
  6. final val BLINK: String("\u001B[5m")

    ANSI blink

    ANSI blink

    Definition Classes
    AnsiColor
  7. final val BLUE: String("\u001B[34m")

    Foreground color for ANSI blue

    Foreground color for ANSI blue

    Definition Classes
    AnsiColor
  8. final val BLUE_B: String("\u001B[44m")

    Background color for ANSI blue

    Background color for ANSI blue

    Definition Classes
    AnsiColor
  9. final val BOLD: String("\u001B[1m")

    ANSI bold

    ANSI bold

    Definition Classes
    AnsiColor
  10. final val CYAN: String("\u001B[36m")

    Foreground color for ANSI cyan

    Foreground color for ANSI cyan

    Definition Classes
    AnsiColor
  11. final val CYAN_B: String("\u001B[46m")

    Background color for ANSI cyan

    Background color for ANSI cyan

    Definition Classes
    AnsiColor
  12. final val GREEN: String("\u001B[32m")

    Foreground color for ANSI green

    Foreground color for ANSI green

    Definition Classes
    AnsiColor
  13. final val GREEN_B: String("\u001B[42m")

    Background color for ANSI green

    Background color for ANSI green

    Definition Classes
    AnsiColor
  14. final val INVISIBLE: String("\u001B[8m")

    ANSI invisible

    ANSI invisible

    Definition Classes
    AnsiColor
  15. final val MAGENTA: String("\u001B[35m")

    Foreground color for ANSI magenta

    Foreground color for ANSI magenta

    Definition Classes
    AnsiColor
  16. final val MAGENTA_B: String("\u001B[45m")

    Background color for ANSI magenta

    Background color for ANSI magenta

    Definition Classes
    AnsiColor
  17. final val RED: String("\u001B[31m")

    Foreground color for ANSI red

    Foreground color for ANSI red

    Definition Classes
    AnsiColor
  18. final val RED_B: String("\u001B[41m")

    Background color for ANSI red

    Background color for ANSI red

    Definition Classes
    AnsiColor
  19. final val RESET: String("\u001B[0m")

    Reset ANSI styles

    Reset ANSI styles

    Definition Classes
    AnsiColor
  20. final val REVERSED: String("\u001B[7m")

    ANSI reversed

    ANSI reversed

    Definition Classes
    AnsiColor
  21. final val UNDERLINED: String("\u001B[4m")

    ANSI underlines

    ANSI underlines

    Definition Classes
    AnsiColor
  22. final val WHITE: String("\u001B[37m")

    Foreground color for ANSI white

    Foreground color for ANSI white

    Definition Classes
    AnsiColor
  23. final val WHITE_B: String("\u001B[47m")

    Background color for ANSI white

    Background color for ANSI white

    Definition Classes
    AnsiColor
  24. final val YELLOW: String("\u001B[33m")

    Foreground color for ANSI yellow

    Foreground color for ANSI yellow

    Definition Classes
    AnsiColor
  25. final val YELLOW_B: String("\u001B[43m")

    Background color for ANSI yellow

    Background color for ANSI yellow

    Definition Classes
    AnsiColor
  26. final def asInstanceOf[T0]: T0

    Forces the compiler to treat the receiver object as having type T0, even though doing so may violate type safety.

    Forces the compiler to treat the receiver object as having type T0, even though doing so may violate type safety.

    This method is useful when you believe you have type information the compiler doesn't, and it also isn't possible to check the type at runtime. In such situations, skipping type safety is the only option.

    It is platform dependent whether asInstanceOf has any effect at runtime. It might do a runtime type test on the erasure of T0, insert a conversion (such as boxing/unboxing), fill in a default value, or do nothing at all.

    In particular, asInstanceOf is not a type test. It does **not** mean:

    this match {
     case x: T0 => x
     case _     => throw ClassCastException("...")

    Use pattern matching or isInstanceOf for type testing instead.

    Situations where asInstanceOf is useful:

    • when flow analysis fails to deduce T0 automatically
    • when down-casting a type parameter or an abstract type member (which cannot be checked at runtime due to type erasure) If there is any doubt and you are able to type test instead, you should do so.

    Be careful of using asInstanceOf when T0 is a primitive type. When T0 is primitive, asInstanceOf may insert a conversion instead of a type test. If your intent is to convert, use a toT method (x.toChar, x.toByte, etc.).

    returns

    the receiver object.

    Definition Classes
    Any
    Exceptions thrown

    ClassCastException if the receiver is not an instance of the erasure of T0, if that can be checked on this platform

  27. def clone(): AnyRef

    Create a copy of the receiver object.

    Create a copy of the receiver object.

    The default implementation of the clone method is platform dependent.

    returns

    a copy of the receiver object.

    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.CloneNotSupportedException]) @native()
    Note

    not specified by SLS as a member of AnyRef

  28. final def eq(arg0: AnyRef): Boolean

    Tests whether the argument (that) is a reference to the receiver object (this).

    Tests whether the argument (that) is a reference to the receiver object (this).

    The eq method implements an equivalence relation on non-null instances of AnyRef, and has three additional properties:

    • It is consistent: for any non-null instances x and y of type AnyRef, multiple invocations of x.eq(y) consistently returns true or consistently returns false.
    • For any non-null instance x of type AnyRef, x.eq(null) and null.eq(x) returns false.
    • null.eq(null) returns true.

    When overriding the equals or hashCode methods, it is important to ensure that their behavior is consistent with reference equality. Therefore, if two objects are references to each other (o1 eq o2), they should be equal to each other (o1 == o2) and they should hash to the same value (o1.hashCode == o2.hashCode).

    returns

    true if the argument is a reference to the receiver object; false otherwise.

    Definition Classes
    AnyRef
  29. def equals(arg0: AnyRef): Boolean

    The equality method for reference types.

    The equality method for reference types. Default implementation delegates to eq.

    See also equals in scala.Any.

    returns

    true if the receiver object is equivalent to the argument; false otherwise.

    Definition Classes
    AnyRef → Any
  30. def err: PrintStream

    The default error, can be overridden by withErr

  31. def finalize(): Unit

    Called by the garbage collector on the receiver object when there are no more references to the object.

    Called by the garbage collector on the receiver object when there are no more references to the object.

    The details of when and if the finalize method is invoked, as well as the interaction between finalize and non-local returns and exceptions, are all platform dependent.

    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.Throwable])
    Note

    not specified by SLS as a member of AnyRef

  32. def flush(): Unit

    Flushes the output stream.

    Flushes the output stream. This function is required when partial output (i.e. output not terminated by a newline character) has to be made visible on the terminal.

  33. final def getClass(): Class[_ <: AnyRef]

    Returns the runtime class representation of the object.

    Returns the runtime class representation of the object.

    returns

    a class object corresponding to the runtime type of the receiver.

    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  34. def hashCode(): Int

    The hashCode method for reference types.

    The hashCode method for reference types. See hashCode in scala.Any.

    returns

    the hash code value for this object.

    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  35. def in: BufferedReader

    The default input, can be overridden by withIn

  36. final def isInstanceOf[T0]: Boolean

    Test whether the dynamic type of the receiver object has the same erasure as T0.

    Test whether the dynamic type of the receiver object has the same erasure as T0.

    Depending on what T0 is, the test is done in one of the below ways:

    • T0 is a non-parameterized class type, e.g. BigDecimal: this method returns true if the value of the receiver object is a BigDecimal or a subtype of BigDecimal.
    • T0 is a parameterized class type, e.g. List[Int]: this method returns true if the value of the receiver object is some List[X] for any X. For example, List(1, 2, 3).isInstanceOf[List[String]] will return true.
    • T0 is some singleton type x.type or literal x: this method returns this.eq(x). For example, x.isInstanceOf[1] is equivalent to x.eq(1)
    • T0 is an intersection X with Y or X & Y: this method is equivalent to x.isInstanceOf[X] && x.isInstanceOf[Y]
    • T0 is a union X | Y: this method is equivalent to x.isInstanceOf[X] || x.isInstanceOf[Y]
    • T0 is a type parameter or an abstract type member: this method is equivalent to isInstanceOf[U] where U is T0's upper bound, Any if T0 is unbounded. For example, x.isInstanceOf[A] where A is an unbounded type parameter will return true for any value of x.

    This is exactly equivalent to the type pattern _: T0

    returns

    true if the receiver object is an instance of erasure of type T0; false otherwise.

    Definition Classes
    Any
    Note

    due to the unexpectedness of List(1, 2, 3).isInstanceOf[List[String]] returning true and x.isInstanceOf[A] where A is a type parameter or abstract member returning true, these forms issue a warning.

  37. final def ne(arg0: AnyRef): Boolean

    Equivalent to !(this eq that).

    Equivalent to !(this eq that).

    returns

    true if the argument is not a reference to the receiver object; false otherwise.

    Definition Classes
    AnyRef
  38. final def notify(): Unit

    Wakes up a single thread that is waiting on the receiver object's monitor.

    Wakes up a single thread that is waiting on the receiver object's monitor.

    Definition Classes
    AnyRef
    Annotations
    @native()
    Note

    not specified by SLS as a member of AnyRef

  39. final def notifyAll(): Unit

    Wakes up all threads that are waiting on the receiver object's monitor.

    Wakes up all threads that are waiting on the receiver object's monitor.

    Definition Classes
    AnyRef
    Annotations
    @native()
    Note

    not specified by SLS as a member of AnyRef

  40. def out: PrintStream

    The default output, can be overridden by withOut

  41. def print(obj: Any): Unit

    Prints an object to out using its toString method.

    Prints an object to out using its toString method.

    obj

    the object to print; may be null.

  42. def printf(text: String, args: Any*): Unit

    Prints its arguments as a formatted string to the default output, based on a string pattern (in a fashion similar to printf in C).

    Prints its arguments as a formatted string to the default output, based on a string pattern (in a fashion similar to printf in C).

    The interpretation of the formatting patterns is described in java.util.Formatter.

    text

    the pattern for formatting the arguments.

    args

    the arguments used to instantiating the pattern.

    Exceptions thrown

    java.lang.IllegalArgumentException if there was a problem with the format string or arguments

  43. def println(x: Any): Unit

    Prints out an object to the default output, followed by a newline character.

    Prints out an object to the default output, followed by a newline character.

    x

    the object to print.

  44. def println(): Unit

    Prints a newline character on the default output.

  45. def setErrDirect(err: PrintStream): Unit
    Attributes
    protected
  46. def setInDirect(in: BufferedReader): Unit
    Attributes
    protected
  47. def setOutDirect(out: PrintStream): Unit
    Attributes
    protected
  48. final def synchronized[T0](arg0: => T0): T0

    Executes the code in body with an exclusive lock on this.

    Executes the code in body with an exclusive lock on this.

    returns

    the result of body

    Definition Classes
    AnyRef
  49. def toString(): String

    Creates a String representation of this object.

    Creates a String representation of this object. The default representation is platform dependent. On the java platform it is the concatenation of the class name, "@", and the object's hashcode in hexadecimal.

    returns

    a String representation of the object.

    Definition Classes
    AnyRef → Any
  50. final def wait(): Unit

    See https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#wait--.

    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.InterruptedException])
    Note

    not specified by SLS as a member of AnyRef

  51. final def wait(arg0: Long, arg1: Int): Unit

    See https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#wait-long-int-

    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.InterruptedException])
    Note

    not specified by SLS as a member of AnyRef

  52. final def wait(arg0: Long): Unit

    See https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#wait-long-.

    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.InterruptedException]) @native()
    Note

    not specified by SLS as a member of AnyRef

  53. def withErr[T](err: OutputStream)(thunk: => T): T

    Sets the default error stream for the duration of execution of one thunk.

    Sets the default error stream for the duration of execution of one thunk.

    err

    the new error stream.

    thunk

    the code to execute with the new error stream active

    returns

    the results of thunk

    See also

    withErr[T](err:PrintStream)(thunk: => T)

  54. def withErr[T](err: PrintStream)(thunk: => T): T

    Set the default error stream for the duration of execution of one thunk.

    Set the default error stream for the duration of execution of one thunk.

    err

    the new error stream.

    thunk

    the code to execute with the new error stream active

    returns

    the results of thunk

    Example:
    1. withErr(Console.out) { err.println("This goes to default _out_") }
    See also

    withErr[T](err:OutputStream)(thunk: => T)

  55. def withIn[T](in: InputStream)(thunk: => T): T

    Sets the default input stream for the duration of execution of one thunk.

    Sets the default input stream for the duration of execution of one thunk.

    in

    the new input stream.

    thunk

    the code to execute with the new input stream active

    returns

    the results of thunk

    See also

    withIn[T](reader:Reader)(thunk: => T)

  56. def withIn[T](reader: Reader)(thunk: => T): T

    Sets the default input stream for the duration of execution of one thunk.

    Sets the default input stream for the duration of execution of one thunk.

    thunk

    the code to execute with the new input stream active

    returns

    the results of thunk

    Example:
    1. val someFile:Reader = openFile("file.txt")
      withIn(someFile) {
        // Reads a line from file.txt instead of default input
        println(readLine)
      }
    See also

    withIn[T](in:InputStream)(thunk: => T)

  57. def withOut[T](out: OutputStream)(thunk: => T): T

    Sets the default output stream for the duration of execution of one thunk.

    Sets the default output stream for the duration of execution of one thunk.

    out

    the new output stream.

    thunk

    the code to execute with the new output stream active

    returns

    the results of thunk

    See also

    withOut[T](out:PrintStream)(thunk: => T)

  58. def withOut[T](out: PrintStream)(thunk: => T): T

    Sets the default output stream for the duration of execution of one thunk.

    Sets the default output stream for the duration of execution of one thunk.

    out

    the new output stream.

    thunk

    the code to execute with the new output stream active

    returns

    the results of thunk

    Example:
    1. withOut(Console.err) { println("This goes to default _error_") }
    See also

    withOut[T](out:OutputStream)(thunk: => T)

Inherited from AnsiColor

Inherited from AnyRef

Inherited from Any

Console Output

These methods provide output via the console.

IO Defaults

These values provide direct access to the standard IO channels

IO Redefinition

These methods allow substituting alternative streams for the duration of a body of code. Threadsafe by virtue of scala.util.DynamicVariable.

ANSI Style and Control Codes

ANSI Black

 

ANSI Red

 

ANSI Green

 

ANSI Yellow

 

ANSI Blue

 

ANSI Magenta

 

ANSI Cyan

 

ANSI White

 

Ungrouped