Scala Cookbook

2.1. Parsing a Number from a String

Problem

You want to convert a String to one of Scala’s numeric types.

Solution

Use the to* methods that are available on a String (courtesy of the StringLike trait):

scala> "100".toInt
res0: Int = 100

scala> "100".toDouble
res1: Double = 100.0

scala> "100".toFloat
res2: Float = 100.0

scala> "1".toLong
res3: Long = 1

scala> "1".toShort
res4: Short = 1

scala> "1".toByte
res5: Byte = 1

Be careful, because these methods can throw the usual Java NumberFormatException:

scala> "foo".toInt
java.lang.NumberFormatException: For input string: "foo"
    at java.lang.NumberFormatException.forInputString(NumberFormatException.java)
    at java.lang.Integer.parseInt(Integer.java:449)
    ... more output here ...

BigInt and BigDecimal instances can also be created directly from strings (and can also throw a NumberFormatException):

scala> val b = BigInt("1")
b: scala.math.BigInt = 1

scala> val b = BigDecimal("3.14159")
b: scala.math.BigDecimal = 3.14159

Handling a base and radix

If you need to perform calculations using bases other than 10, you’ll find the toInt method in the Scala Int class doesn’t have a method that lets you pass in a base and radix. To solve this problem, use the parseInt method in the java.lang.Integer class, as shown in these examples:

scala> Integer.parseInt("1", 2)
res0: Int = 1

scala> Integer.parseInt("10", 2)
res1: Int = 2

scala> Integer.parseInt("100", 2)
res2: Int = 4

scala> Integer.parseInt("1", 8)
res3: Int = 1

scala> Integer.parseInt("10", 8) res4: Int ...