object Console extends DeprecatedConsole with 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
- Since
1.0
- Grouped
- Alphabetic
- By Inheritance
- Console
- AnsiColor
- DeprecatedConsole
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Console Output
These methods provide output via the console.
-
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.
-
def
print(obj: Any): Unit
Prints an object to
out
using itstoString
method.Prints an object to
out
using itstoString
method.- obj
the object to print; may be null.
-
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
-
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.
-
def
println(): Unit
Prints a newline character on the default output.
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.
-
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)
-
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
withErr(Console.out) { err.println("This goes to default _out_") }
- See also
withErr[T](err:OutputStream)(thunk: =>T)
Example: -
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)
-
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
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)
Example: -
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)
-
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
withOut(Console.err) { println("This goes to default _error_") }
- See also
withOut[T](out:OutputStream)(thunk: => T)
Example:
ANSI Style and Control Codes
-
final
val
BLINK: String("\u001B[5m")
ANSI blink
ANSI blink
- Definition Classes
- AnsiColor
-
final
val
BOLD: String("\u001B[1m")
ANSI bold
ANSI bold
- Definition Classes
- AnsiColor
-
final
val
INVISIBLE: String("\u001B[8m")
ANSI invisible
ANSI invisible
- Definition Classes
- AnsiColor
-
final
val
RESET: String("\u001B[0m")
Reset ANSI styles
Reset ANSI styles
- Definition Classes
- AnsiColor
-
final
val
REVERSED: String("\u001B[7m")
ANSI reversed
ANSI reversed
- Definition Classes
- AnsiColor
-
final
val
UNDERLINED: String("\u001B[4m")
ANSI underlines
ANSI underlines
- Definition Classes
- AnsiColor
ANSI Black
ANSI Red
ANSI Green
ANSI Yellow
ANSI Blue
ANSI Magenta
ANSI Cyan
ANSI White
Ungrouped
-
def
readBoolean(): Boolean
- Definition Classes
- DeprecatedConsole
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use the method in scala.io.StdIn
-
def
readByte(): Byte
- Definition Classes
- DeprecatedConsole
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use the method in scala.io.StdIn
-
def
readChar(): Char
- Definition Classes
- DeprecatedConsole
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use the method in scala.io.StdIn
-
def
readDouble(): Double
- Definition Classes
- DeprecatedConsole
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use the method in scala.io.StdIn
-
def
readFloat(): Float
- Definition Classes
- DeprecatedConsole
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use the method in scala.io.StdIn
-
def
readInt(): Int
- Definition Classes
- DeprecatedConsole
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use the method in scala.io.StdIn
-
def
readLine(text: String, args: Any*): String
- Definition Classes
- DeprecatedConsole
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use the method in scala.io.StdIn
-
def
readLine(): String
- Definition Classes
- DeprecatedConsole
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use the method in scala.io.StdIn
-
def
readLong(): Long
- Definition Classes
- DeprecatedConsole
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use the method in scala.io.StdIn
-
def
readShort(): Short
- Definition Classes
- DeprecatedConsole
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use the method in scala.io.StdIn
-
def
readf(format: String): List[Any]
- Definition Classes
- DeprecatedConsole
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use the method in scala.io.StdIn
-
def
readf1(format: String): Any
- Definition Classes
- DeprecatedConsole
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use the method in scala.io.StdIn
-
def
readf2(format: String): (Any, Any)
- Definition Classes
- DeprecatedConsole
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use the method in scala.io.StdIn
-
def
readf3(format: String): (Any, Any, Any)
- Definition Classes
- DeprecatedConsole
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use the method in scala.io.StdIn
-
def
setErr(err: OutputStream): Unit
Sets the default error stream.
Sets the default error stream.
- err
the new error stream.
- Definition Classes
- DeprecatedConsole
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use withErr
-
def
setErr(err: PrintStream): Unit
Sets the default error stream.
Sets the default error stream.
- err
the new error stream.
- Definition Classes
- DeprecatedConsole
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use withErr
-
def
setIn(in: InputStream): Unit
Sets the default input stream.
Sets the default input stream.
- in
the new input stream.
- Definition Classes
- DeprecatedConsole
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use withIn
-
def
setIn(reader: Reader): Unit
Sets the default input stream.
Sets the default input stream.
- reader
specifies the new input stream.
- Definition Classes
- DeprecatedConsole
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use withIn
-
def
setOut(out: OutputStream): Unit
Sets the default output stream.
Sets the default output stream.
- out
the new output stream.
- Definition Classes
- DeprecatedConsole
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use withOut
-
def
setOut(out: PrintStream): Unit
Sets the default output stream.
Sets the default output stream.
- out
the new output stream.
- Definition Classes
- DeprecatedConsole
- Annotations
- @deprecated
- Deprecated
(Since version 2.11.0) use withOut
This is the documentation for the Scala standard library.
Package structure
The scala package contains core types like
Int
,Float
,Array
orOption
which are accessible in all Scala compilation units without explicit qualification or imports.Notable packages include:
scala.collection
and its sub-packages contain Scala's collections frameworkscala.collection.immutable
- Immutable, sequential data-structures such asVector
,List
,Range
,HashMap
orHashSet
scala.collection.mutable
- Mutable, sequential data-structures such asArrayBuffer
,StringBuilder
,HashMap
orHashSet
scala.collection.concurrent
- Mutable, concurrent data-structures such asTrieMap
scala.collection.parallel.immutable
- Immutable, parallel data-structures such asParVector
,ParRange
,ParHashMap
orParHashSet
scala.collection.parallel.mutable
- Mutable, parallel data-structures such asParArray
,ParHashMap
,ParTrieMap
orParHashSet
scala.concurrent
- Primitives for concurrent programming such asFutures
andPromises
scala.io
- Input and output operationsscala.math
- Basic math functions and additional numeric types likeBigInt
andBigDecimal
scala.sys
- Interaction with other processes and the operating systemscala.util.matching
- Regular expressionsOther packages exist. See the complete list on the right.
Additional parts of the standard library are shipped as separate libraries. These include:
scala.reflect
- Scala's reflection API (scala-reflect.jar)scala.xml
- XML parsing, manipulation, and serialization (scala-xml.jar)scala.swing
- A convenient wrapper around Java's GUI framework called Swing (scala-swing.jar)scala.util.parsing
- Parser combinators (scala-parser-combinators.jar)Automatic imports
Identifiers in the scala package and the
scala.Predef
object are always in scope by default.Some of these identifiers are type aliases provided as shortcuts to commonly used classes. For example,
List
is an alias forscala.collection.immutable.List
.Other aliases refer to classes provided by the underlying platform. For example, on the JVM,
String
is an alias forjava.lang.String
.