How to handle very large numbers in Scala (BigInt, BigDecimal)

By Alvin Alexander. Last updated: June 8, 2020

This is an excerpt from the Scala Cookbook (partially modified for the internet). This is Recipe 2.6, “Handling Very Large Numbers in Scala.”

Problem

You’re writing a Scala application and need to use very large integer or decimal numbers.

Solution

Use the Scala BigInt and BigDecimal classes. You can create a BigInt:

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

or a BigDecimal:

 scala> var 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 in Table 1-1, 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