Method formatNumericValue

core/src/main/java/com/google/common/truth/Fact.java:100–135

Formats the given numeric value as a string with delimiting commas. Note: only Long, Integer, Float, Double and BigDecimal are supported.

(@Nullable Number value)

   * BigDecimal} are supported.
   */
  static String formatNumericValue(@Nullable Number value) {
    if (value == null) {
      return "null";
    }
    // the value must be a numeric type
    checkArgument(
        value instanceof Long
            || value instanceof Integer
            || value instanceof Float
            || value instanceof Double
            || value instanceof BigDecimal,
        "Value (%s) must be either a Long, Integer, Float, Double, or BigDecimal.",
        value);

    // DecimalFormat is not available on all platforms, so we do the formatting manually.

    if (!(value instanceof BigDecimal) && isInfiniteOrNaN(value.doubleValue())) {
      return value.toString();
    }
    String stringValue =
        value instanceof Double
            ? doubleToString((double) value)
            : value instanceof Float //
                ? floatToString((float) value)
                : value.toString();
    if (stringValue.contains("E")) {
      return stringValue;
    }
    int decimalIndex = stringValue.indexOf('.');
    if (decimalIndex == -1) {
      return formatWholeNumericValue(stringValue);
    }
    String wholeNumbers = stringValue.substring(0, decimalIndex);
    String decimal = stringValue.substring(decimalIndex);
    return formatWholeNumericValue(wholeNumbers) + decimal;
  }

  private static boolean isInfiniteOrNaN(double d) {
    return Double.isInfinite(d) || Double.isNaN(d);