JDK 12 Early Access Build 24 introduces support for Compact Number Formatting. The JDK-8188147 (Compact Number Formatting support) CSR's "Summary" is the simple sentence, "Adding support for the compact/short number formatting in JDK." That same CSR also provides a detailed "Solution" section that provides background on providing numbers in multiple compact forms for each Locale and the constructs/APIs added to the JDK to support this functionality (new class, new enum, new methods, etc.)

The representations of compact and short formats of numbers in each locale are based on the Unicode Common Locale Data Repository (CLDR). A newly added class, java.text.CompactNumberFormat , has class-level Javadoc comments that provide quite a bit of detail regarding how numbers are expressed in "short" and "long" compact number formats. That class's Javadoc comments also specify compact number patterns, formatting, parsing, and rounding (RoundingMode.HALF_EVEN by default) related to custom number formats.

In the request for review of the addition of compact number formatting to JDK 12, Nishit Jain writes:

The existing NumberFormat API provides locale based support for formatting and parsing numbers which includes formatting decimal, percent, currency etc, but the support for formatting a number into a human readable or compact form is missing. This RFE adds that feature to format a decimal number in a compact format (e.g. 1000 -> 1K, 1000000 -> 1M in en_US locale), which is useful for the environment where display space is limited, so that the formatted string can be displayed in that limited space. It is defined by LDML's specification for Compact Number Formats. http://unicode.org/reports/tr35/tr35-numbers.html#Compact_Number_Formats

It is probably easiest to understand compact number formatting via code example. The following class ( CompactNumberFormatDemo ) was compiled and executed against JDK 12 Early Access Build 24.

package dustin.examples.jdk12.format; import static java.lang.System.out; import java.text.NumberFormat; import java.util.Locale; /** * Demonstrate Compact Number Format support added to * JDK 12 as of Early Access Build 24 (see also * JDK-8177552: Compact Number Formatting support). */ public class CompactNumberFormatDemo { private static void demonstrateCompactNumberFormatting(final long numberToFormat) { final NumberFormat numberFormatDefault = NumberFormat.getCompactNumberInstance(); final NumberFormat numberFormatUsLong = NumberFormat.getCompactNumberInstance(Locale.US, NumberFormat.Style.LONG); final NumberFormat numberFormatUkShort = NumberFormat.getCompactNumberInstance(Locale.UK, NumberFormat.Style.SHORT); final NumberFormat numberFormatUkLong = NumberFormat.getCompactNumberInstance(Locale.UK, NumberFormat.Style.LONG); final NumberFormat numberFormatFrShort = NumberFormat.getCompactNumberInstance(Locale.FRANCE, NumberFormat.Style.SHORT); final NumberFormat numberFormatFrLong = NumberFormat.getCompactNumberInstance(Locale.FRANCE, NumberFormat.Style.LONG); final NumberFormat numberFormatGrShort = NumberFormat.getCompactNumberInstance(Locale.GERMANY, NumberFormat.Style.SHORT); final NumberFormat numberFormatGrLong = NumberFormat.getCompactNumberInstance(Locale.GERMANY, NumberFormat.Style.LONG); final NumberFormat numberFormatItShort = NumberFormat.getCompactNumberInstance(Locale.ITALY, NumberFormat.Style.SHORT); final NumberFormat numberFormatItLong = NumberFormat.getCompactNumberInstance(Locale.ITALY, NumberFormat.Style.LONG); out.println("Demonstrating Compact Number Formatting on '" + numberToFormat + "':"); out.println("\tDefault: " + numberFormatDefault.format(numberToFormat)); out.println("\tUS/Long: " + numberFormatUsLong.format(numberToFormat)); out.println("\tUK/Short: " + numberFormatUkShort.format(numberToFormat)); out.println("\tUK/Long: " + numberFormatUkLong.format(numberToFormat)); out.println("\tFR/Short: " + numberFormatFrShort.format(numberToFormat)); out.println("\tFR/Long: " + numberFormatFrLong.format(numberToFormat)); out.println("\tDE/Short: " + numberFormatGrShort.format(numberToFormat)); out.println("\tDE/Long: " + numberFormatGrLong.format(numberToFormat)); out.println("\tIT/Short: " + numberFormatItShort.format(numberToFormat)); out.println("\tIT/Long: " + numberFormatItLong.format(numberToFormat)); } /** * Main demonstration executable. * @param arguments Command-line arguments: none expected. */ public static void main(final String[] arguments) { demonstrateCompactNumberFormatting(15); demonstrateCompactNumberFormatting(150); demonstrateCompactNumberFormatting(1500); demonstrateCompactNumberFormatting(15000); demonstrateCompactNumberFormatting(150000); demonstrateCompactNumberFormatting(1500000); demonstrateCompactNumberFormatting(15000000); } }





When executed, the above code writes the following to standard output:

Demonstrating Compact Number Formatting on '15': Default: 15 US/Long: 15 UK/Short: 15 UK/Long: 15 FR/Short: 15 FR/Long: 15 DE/Short: 15 DE/Long: 15 IT/Short: 15 IT/Long: 15 Demonstrating Compact Number Formatting on '150': Default: 150 US/Long: 150 UK/Short: 150 UK/Long: 150 FR/Short: 150 FR/Long: 150 DE/Short: 150 DE/Long: 150 IT/Short: 150 IT/Long: 150 Demonstrating Compact Number Formatting on '1500': Default: 2K US/Long: 2 thousand UK/Short: 2K UK/Long: 2 thousand FR/Short: 2 k FR/Long: 2 millier DE/Short: 1.500 DE/Long: 2 Tausend IT/Short: 1.500 IT/Long: 2 mille Demonstrating Compact Number Formatting on '15000': Default: 15K US/Long: 15 thousand UK/Short: 15K UK/Long: 15 thousand FR/Short: 15 k FR/Long: 15 mille DE/Short: 15.000 DE/Long: 15 Tausend IT/Short: 15.000 IT/Long: 15 mila Demonstrating Compact Number Formatting on '150000': Default: 150K US/Long: 150 thousand UK/Short: 150K UK/Long: 150 thousand FR/Short: 150 k FR/Long: 150 mille DE/Short: 150.000 DE/Long: 150 Tausend IT/Short: 150.000 IT/Long: 150 mila Demonstrating Compact Number Formatting on '1500000': Default: 2M US/Long: 2 million UK/Short: 2M UK/Long: 2 million FR/Short: 2 M FR/Long: 2 million DE/Short: 2 Mio. DE/Long: 2 Million IT/Short: 2 Mln IT/Long: 2 milione Demonstrating Compact Number Formatting on '15000000': Default: 15M US/Long: 15 million UK/Short: 15M UK/Long: 15 million FR/Short: 15 M FR/Long: 15 million DE/Short: 15 Mio. DE/Long: 15 Millionen IT/Short: 15 Mln IT/Long: 15 milioni





The compact number format support that has been added to JDK 12 via Early Access Build 24 allows for formatting and parsing numeric representations in a locale-specific "long" or "short" compact forms.