Scala Cookbook

2.9. Formatting Numbers and Currency

Problem

You want to format numbers or currency to control decimal places and commas, typically for printed output.

Solution

For basic number formatting, use the f string interpolator shown in Recipe 1.4:

scala> val pi = scala.math.Pi
pi: Double = 3.141592653589793

scala> println(f"$pi%1.5f")
3.14159

A few more examples demonstrate the technique:

scala> f"$pi%1.5f"
res0: String = 3.14159

scala> f"$pi%1.2f"
res1: String = 3.14

scala> f"$pi%06.2f"
res2: String = 003.14

If you’re using a version of Scala prior to 2.10, or prefer the explicit use of the format method, you can write the code like this instead:

scala> "%06.2f".format(pi)
res3: String = 003.14

A simple way to add commas is to use the getIntegerInstance method of the java.text.NumberFormat class:

scala> val formatter = java.text.NumberFormat.getIntegerInstance
formatter: java.text.NumberFormat = java.text.DecimalFormat@674dc

scala> formatter.format(10000)
res0: String = 10,000

scala> formatter.format(1000000)
res1: String = 1,000,000

You can also set a locale with the getIntegerInstance method:

scala> val locale = new java.util.Locale("de", "DE")
locale: java.util.Locale = de_DE

scala> val formatter = java.text.NumberFormat.getIntegerInstance(locale)
formatter: java.text.NumberFormat = java.text.DecimalFormat@674dc

scala> formatter.format(1000000)
res2: String = 1.000.000

You can handle floating-point values with a formatter returned by getInstance:

scala> val formatter = java.text.NumberFormat.getInstance ...