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 ...
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