How to take input from a user in Scala? - scala

Question

I want to take input from the user. Can you please tell me how to ask for user input as a string in Scala?

Answer 1

In Scala 2.11 use
scala.io.StdIn.readLine()
instead of the deprecated Console.readLine.

Answer 2

Here is a standard way to read Integer values
val a = scala.io.StdIn.readInt()
println("The value of a is " + a)
similarly
def readBoolean(): Boolean
Reads a Boolean value from an entire line from stdin.
def readByte(): Byte
Reads a Byte value from an entire line from stdin.
def readChar(): Char
Reads a Char value from an entire line from stdin.
def readDouble(): Double
Reads a Double value from an entire line from stdin.
def readFloat(): Float
Reads a Float value from an entire line from stdin.
def readInt(): Int
Reads an Int value from an entire line from stdin.
def readLine(text: String, args: Any*): String
Prints formatted text to stdout and reads a full line from stdin.
def readLine(): String
Reads a full line from stdin.
def readLong(): Long
Reads a Long value from an entire line from stdin.
def readShort(): Short
Reads a Short value from an entire line from stdin.
def readf(format: String): List[Any]
Reads in structured input from stdin as specified by the format specifier.
def readf1(format: String): Any
Reads in structured input from stdin as specified by the format specifier, returning
only the first value extracted, according to the format specification.
def readf2(format: String): (Any, Any)
Reads in structured input from stdin as specified by the format specifier, returning
only the first two values extracted, according to the format specification.
def readf3(format: String): (Any, Any, Any)
Reads in structured input from stdin as specified by the format specifier, returning
only the first three values extracted, according to the format specification.
Similarly if you want to read multiple user inputs from the same line ex: name, age, weight you can use the Scanner object
import java.util.Scanner
// simulated input
val input = "Joe 33 200.0"
val line = new Scanner(input)
val name = line.next
val age = line.nextInt
val weight = line.nextDouble
abridged from Scala Cookbook: Recipes for Object-Oriented and Functional Programming by Alvin Alexander

Answer 3

From the Scala maling list (formatting and links were updated):
Short answer:
readInt
Long answer:
If you want to read from the terminal, check out Console.scala.
You can use these functions like so:
Console.readInt
Also, for your convenience, Predef.scala
automatically defines some shortcuts to functions in Console. Since
stuff in Predef is always and everywhere imported automatically, you
can use them like so:
readInt

Answer 4

object InputTest extends App{
println("Type something : ")
val input = scala.io.StdIn.readLine()
println("Did you type this ? " + input)
}
This way you can ask input.
scala.io.StdIn.readLine()

Answer 5

You can take a user String input using readLine().
import scala.io.StdIn._
object q1 {
def main(args:Array[String]):Unit={
println("Enter your name : ")
val a = readLine()
println("My name is : "+a)
}
}
Or you can use the scanner class to take user input.
import java.util.Scanner;
object q1 {
def main(args:Array[String]):Unit={
val scanner = new Scanner(System.in)
println("Enter your name : ")
val a = scanner.nextLine()
println("My name is : "+a)
}
}

Answer 6

Simple Example for Reading Input from User
val scanner = new java.util.Scanner(System.in)
scala> println("What is your name") What is your name
scala> val name = scanner.nextLine()
name: String = VIRAJ
scala> println(s"My Name is $name")
My Name is VIRAJ
Also we can use Read Line
val name = readLine("What is your name ")
What is your name name: String = Viraj

Answer 7

In Scala 2:
import java.io._
object Test {
// Read user input, output
def main(args: Array[String]) {
// create a file writer
var writer = new PrintWriter(new File("output.txt"))
// read an int from standard input
print("Enter the number of lines to read in: ")
val x: Int = scala.io.StdIn.readLine.toInt
// read in x number of lines from standard input
var i=0
while (i < x) {
var str: String = scala.io.StdIn.readLine
writer.write(str + "\n")
i = i + 1
}
// close the writer
writer.close
}
}
This code gets input from user and outputs it:
[input] Enter the number of lines to read in: 2
one
two
[output] output.txt
one
two

Answer 8

Using a thread to poll the input-readLine:
// keystop1.sc
// In Scala- or SBT console/Quick-REPL: :load keystop1.sc
// As Script: scala -savecompiled keystop1.sc
#volatile var isRunning = true
#volatile var isPause = false
val tInput: Thread = new Thread {
override def run: Unit = {
var status = ""
while (isRunning) {
this.synchronized {
status = scala.io.StdIn.readLine()
status match {
case "s" => isRunning = false
case "p" => isPause = true
case "r" => isRunning = true;isPause = false
case _ => isRunning = false;isPause = false
}
println(s"New status is: $status")
}
}
}
}
tInput.start
var count = 0
var pauseCount = 0
while (isRunning && count < 10){
println(s"still running long lasting job! $count")
if (count % 3 == 0) println("(Please press [each + ENTER]: s to stop, p to pause, r to run again!)")
count += 1
Thread sleep(2000) // simulating heavy computation
while (isPause){
println(s"Taking a break ... $pauseCount")
Thread sleep(1000)
pauseCount += 1
if (pauseCount >= 10){
isPause = false
pauseCount = 0
println(s"Taking a break ... timeout occurred!")
}
}
}
isRunning = false
println(s"Computation stopped, please press Enter!")
tInput.join()
println(s"Ok, thank you, good bye!")

Answer 9

readLine() lets you prompt the user and read their input as a String
val name = readLine("What's your name? ")

Answer 10

please try
scala> readint
please try this method