How to use BigInt and BigDecimal when you need very large numbers in Scala

By Alvin Alexander. Last updated: July 31, 2022

Scala FAQ: I’m writing an application and I need to use very large integer or decimal (floating-point) numbers; what’s the best approach?

Solution

Use the Scala BigInt and BigDecimal classes. You can create a BigInt instead of an Int or Long:

scala> val b = BigInt(1234567890)
b: scala.math.BigInt = 1234567890

or a BigDecimal instead of a Double:

scala> val b = BigDecimal(123456.789)
b: scala.math.BigDecimal = 123456.789

Unlike their Java equivalents, these classes support all the operators you’re used to using with numeric types:

scala> b + b
res0: scala.math.BigInt = 2469135780

scala> b * b
res1: scala.math.BigInt = 1524157875019052100

scala> b += 1

scala> println(b)
1234567891

You can convert them to other numeric types:

scala> b.toInt
res2: Int = 1234567891

scala> b.toLong
res3: Long = 1234567891

scala> b.toFloat
res4: Float = 1.23456794E9

scala> b.toDouble
res5: Double = 1.234567891E9

To help avoid errors, you can also test them first to see if they can be converted to other numeric types:

scala> b.isValidByte
res6: Boolean = false

scala> b.isValidChar
res7: Boolean = false

scala> b.isValidShort
res8: Boolean = false

scala> if (b.isValidInt) b.toInt
res9: AnyVal = 1234567890

Discussion

Although the Scala BigInt and BigDecimal classes are backed by the Java BigInteger and BigDecimal classes, they are simpler to use than their Java counterparts. As you can see in the examples, they work just like other numeric types, and they’re also mutable (as you saw in the += example). These are nice improvements over the Java classes.

Before using BigInt or BigDecimal, you can check the maximum values that the other Scala numeric types can handle here:

Data type   Range
---------   --------------------------------------
Char        16-bit unsigned Unicode character
Byte        8-bit signed value
Short       16-bit signed value
Int         32-bit signed value
Long        64-bit signed value
Float       32-bit IEEE 754 single precision float
Double      64-bit IEEE 754 single precision float

or by checking their MaxValue in the REPL:

scala> Byte.MaxValue
res0: Byte = 127

scala> Short.MaxValue
res1: Short = 32767

scala> Int.MaxValue
res2: Int = 2147483647

scala> Long.MaxValue
res3: Long = 9223372036854775807

scala> Double.MaxValue
res4: Double = 1.7976931348623157E308

Depending on your needs, you may also be able to use the PositiveInfinity and NegativeInfinity of the standard numeric types:

scala> Double.PositiveInfinity
res0: Double = Infinity

scala> Double.NegativeInfinity
res1: Double = -Infinity

scala> 1.7976931348623157E308 > Double.PositiveInfinity
res45: Boolean = false