Class NumberFormatter


  • public final class NumberFormatter
    extends java.lang.Object
    The main entrypoint to the localized number formatting library introduced in ICU 60. Basic usage examples:
     // Most basic usage:
     NumberFormatter.withLocale(...).format(123).toString();  // 1,234 in en-US
    
     // Custom notation, unit, and rounding strategy:
     NumberFormatter.with()
         .notation(Notation.compactShort())
         .unit(Currency.getInstance("EUR"))
         .precision(Precision.maxDigits(2))
         .locale(...)
         .format(1234)
         .toString();  // €1.2K in en-US
    
     // Create a formatter in a private static final field:
     private static final LocalizedNumberFormatter formatter = NumberFormatter.withLocale(...)
         .unit(NoUnit.PERCENT)
         .precision(Precision.fixedFraction(3));
     formatter.format(5.9831).toString();  // 5.983% in en-US
    
     // Create a "template" in a private static final field but without setting a locale until the call site:
     private static final UnlocalizedNumberFormatter template = NumberFormatter.with()
         .sign(SignDisplay.ALWAYS)
         .unitWidth(UnitWidth.FULL_NAME);
     template.locale(...).format(new Measure(1234, MeasureUnit.METER)).toString();  // +1,234 meters in en-US
     

    This API offers more features than DecimalFormat and is geared toward new users of ICU.

    NumberFormatter instances are immutable and thread safe. This means that invoking a configuration method has no effect on the receiving instance; you must store and use the new number formatter instance it returns instead.

     UnlocalizedNumberFormatter formatter = UnlocalizedNumberFormatter.with()
             .notation(Notation.scientific());
     formatter.precision(Precision.maxFraction(2)); // does nothing!
     formatter.locale(ULocale.ENGLISH).format(9.8765).toString(); // prints "9.8765E0", not "9.88E0"
     

    This API is based on the fluent design pattern popularized by libraries such as Google's Guava. For extensive details on the design of this API, read the design doc.

    Author:
    Shane Carr
    • Method Detail

      • withLocale

        public static LocalizedNumberFormatter withLocale​(java.util.Locale locale)
        Call this method at the beginning of a NumberFormatter fluent chain in which the locale is known at the call site.
        Parameters:
        locale - The locale from which to load formats and symbols for number formatting.
        Returns:
        A LocalizedNumberFormatter, to be used for chaining.
      • withLocale

        public static LocalizedNumberFormatter withLocale​(ULocale locale)
        Call this method at the beginning of a NumberFormatter fluent chain in which the locale is known at the call site.
        Parameters:
        locale - The locale from which to load formats and symbols for number formatting.
        Returns:
        A LocalizedNumberFormatter, to be used for chaining.
      • forSkeleton

        public static UnlocalizedNumberFormatter forSkeleton​(java.lang.String skeleton)
        Call this method at the beginning of a NumberFormatter fluent chain to create an instance based on a given number skeleton string.
        Parameters:
        skeleton - The skeleton string off of which to base this NumberFormatter.
        Returns:
        An UnlocalizedNumberFormatter, to be used for chaining.
        Throws:
        SkeletonSyntaxException - If the given string is not a valid number formatting skeleton.
      • fromDecimalFormat

        @Deprecated
        public static UnlocalizedNumberFormatter fromDecimalFormat​(com.ibm.icu.impl.number.DecimalFormatProperties properties,
                                                                   DecimalFormatSymbols symbols,
                                                                   com.ibm.icu.impl.number.DecimalFormatProperties exportedProperties)
        Deprecated.
        ICU 60 This API is ICU internal only.
        Note: In Java, since NumberPropertyMapper is package-private, this method is here so that it is accessible to tests.