xref: /aosp_15_r20/external/icu/libicu/cts_headers/unicode/decimfmt.h (revision 0e209d3975ff4a8c132096b14b0e9364a753506e)

// © 2016 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html
/*
********************************************************************************
*   Copyright (C) 1997-2016, International Business Machines
*   Corporation and others.  All Rights Reserved.
********************************************************************************
*
* File DECIMFMT.H
*
* Modification History:
*
*   Date        Name        Description
*   02/19/97    aliu        Converted from java.
*   03/20/97    clhuang     Updated per C++ implementation.
*   04/03/97    aliu        Rewrote parsing and formatting completely, and
*                           cleaned up and debugged.  Actually works now.
*   04/17/97    aliu        Changed DigitCount to int per code review.
*   07/10/97    helena      Made ParsePosition a class and get rid of the function
*                           hiding problems.
*   09/09/97    aliu        Ported over support for exponential formats.
*   07/20/98    stephen     Changed documentation
*   01/30/13    emmons      Added Scaling methods
********************************************************************************
*/

#ifndef DECIMFMT_H
#define DECIMFMT_H

#include "unicode/utypes.h"

#if U_SHOW_CPLUSPLUS_API

/**
 * \file
 * \brief C++ API: Compatibility APIs for decimal formatting.
 */

#if !UCONFIG_NO_FORMATTING

#include "unicode/dcfmtsym.h"
#include "unicode/numfmt.h"
#include "unicode/locid.h"
#include "unicode/fpositer.h"
#include "unicode/stringpiece.h"
#include "unicode/curramt.h"
#include "unicode/enumset.h"

U_NAMESPACE_BEGIN

class CurrencyPluralInfo;
class CompactDecimalFormat;

namespace number {
class LocalizedNumberFormatter;
namespace impl {
class DecimalQuantity;
struct DecimalFormatFields;
class UFormattedNumberData;
}
}

namespace numparse::impl {
class NumberParserImpl;
}

/**
 * **IMPORTANT:** New users are strongly encouraged to see if
 * numberformatter.h fits their use case.  Although not deprecated, this header
 * is provided for backwards compatibility only.
 *
 * DecimalFormat is a concrete subclass of NumberFormat that formats decimal
 * numbers. It has a variety of features designed to make it possible to parse
 * and format numbers in any locale, including support for Western, Arabic, or
 * Indic digits.  It also supports different flavors of numbers, including
 * integers ("123"), fixed-point numbers ("123.4"), scientific notation
 * ("1.23E4"), percentages ("12%"), and currency amounts ("$123", "USD123",
 * "123 US dollars").  All of these flavors can be easily localized.
 *
 * To obtain a NumberFormat for a specific locale (including the default
 * locale) call one of NumberFormat's factory methods such as
 * createInstance(). Do not call the DecimalFormat constructors directly, unless
 * you know what you are doing, since the NumberFormat factory methods may
 * return subclasses other than DecimalFormat.
 *
 * **Example Usage**
 *
 * \code
 *     // Normally we would have a GUI with a menu for this
 *     int32_t locCount;
 *     const Locale* locales = NumberFormat::getAvailableLocales(locCount);
 *
 *     double myNumber = -1234.56;
 *     UErrorCode success = U_ZERO_ERROR;
 *     NumberFormat* form;
 *
 *     // Print out a number with the localized number, currency and percent
 *     // format for each locale.
 *     UnicodeString countryName;
 *     UnicodeString displayName;
 *     UnicodeString str;
 *     UnicodeString pattern;
 *     Formattable fmtable;
 *     for (int32_t j = 0; j < 3; ++j) {
 *         cout << endl << "FORMAT " << j << endl;
 *         for (int32_t i = 0; i < locCount; ++i) {
 *             if (locales[i].getCountry(countryName).size() == 0) {
 *                 // skip language-only
 *                 continue;
 *             }
 *             switch (j) {
 *             case 0:
 *                 form = NumberFormat::createInstance(locales[i], success ); break;
 *             case 1:
 *                 form = NumberFormat::createCurrencyInstance(locales[i], success ); break;
 *             default:
 *                 form = NumberFormat::createPercentInstance(locales[i], success ); break;
 *             }
 *             if (form) {
 *                 str.remove();
 *                 pattern = ((DecimalFormat*)form)->toPattern(pattern);
 *                 cout << locales[i].getDisplayName(displayName) << ": " << pattern;
 *                 cout << "  ->  " << form->format(myNumber,str) << endl;
 *                 form->parse(form->format(myNumber,str), fmtable, success);
 *                 delete form;
 *             }
 *         }
 *     }
 * \endcode
 *
 * **Another example use createInstance(style)**
 *
 * \code
 * // Print out a number using the localized number, currency,
 * // percent, scientific, integer, iso currency, and plural currency
 * // format for each locale</strong>
 * Locale* locale = new Locale("en", "US");
 * double myNumber = 1234.56;
 * UErrorCode success = U_ZERO_ERROR;
 * UnicodeString str;
 * Formattable fmtable;
 * for (int j=NumberFormat::kNumberStyle;
 *      j<=NumberFormat::kPluralCurrencyStyle;
 *      ++j) {
 *     NumberFormat* form = NumberFormat::createInstance(locale, j, success);
 *     str.remove();
 *     cout << "format result " << form->format(myNumber, str) << endl;
 *     format->parse(form->format(myNumber, str), fmtable, success);
 *     delete form;
 * }
 * \endcode
 *
 *
 * <p><strong>Patterns</strong>
 *
 * <p>A DecimalFormat consists of a <em>pattern</em> and a set of
 * <em>symbols</em>.  The pattern may be set directly using
 * applyPattern(), or indirectly using other API methods which
 * manipulate aspects of the pattern, such as the minimum number of integer
 * digits.  The symbols are stored in a DecimalFormatSymbols
 * object.  When using the NumberFormat factory methods, the
 * pattern and symbols are read from ICU's locale data.
 *
 * <p><strong>Special Pattern Characters</strong>
 *
 * <p>Many characters in a pattern are taken literally; they are matched during
 * parsing and output unchanged during formatting.  Special characters, on the
 * other hand, stand for other characters, strings, or classes of characters.
 * For example, the '#' character is replaced by a localized digit.  Often the
 * replacement character is the same as the pattern character; in the U.S. locale,
 * the ',' grouping character is replaced by ','.  However, the replacement is
 * still happening, and if the symbols are modified, the grouping character
 * changes.  Some special characters affect the behavior of the formatter by
 * their presence; for example, if the percent character is seen, then the
 * value is multiplied by 100 before being displayed.
 *
 * <p>To insert a special character in a pattern as a literal, that is, without
 * any special meaning, the character must be quoted.  There are some exceptions to
 * this which are noted below.
 *
 * <p>The characters listed here are used in non-localized patterns.  Localized
 * patterns use the corresponding characters taken from this formatter's
 * DecimalFormatSymbols object instead, and these characters lose
 * their special status.  Two exceptions are the currency sign and quote, which
 * are not localized.
 *
 * <table border=0 cellspacing=3 cellpadding=0>
 *   <tr bgcolor="#ccccff">
 *     <td align=left><strong>Symbol</strong>
 *     <td align=left><strong>Location</strong>
 *     <td align=left><strong>Localized?</strong>
 *     <td align=left><strong>Meaning</strong>
 *   <tr valign=top>
 *     <td><code>0</code>
 *     <td>Number
 *     <td>Yes
 *     <td>Digit
 *   <tr valign=top bgcolor="#eeeeff">
 *     <td><code>1-9</code>
 *     <td>Number
 *     <td>Yes
 *     <td>'1' through '9' indicate rounding.
 *   <tr valign=top>
 *     <td><code>\htmlonly&#x40;\endhtmlonly</code> <!--doxygen doesn't like @-->
 *     <td>Number
 *     <td>No
 *     <td>Significant digit
 *   <tr valign=top bgcolor="#eeeeff">
 *     <td><code>#</code>
 *     <td>Number
 *     <td>Yes
 *     <td>Digit, zero shows as absent
 *   <tr valign=top>
 *     <td><code>.</code>
 *     <td>Number
 *     <td>Yes
 *     <td>Decimal separator or monetary decimal separator
 *   <tr valign=top bgcolor="#eeeeff">
 *     <td><code>-</code>
 *     <td>Number
 *     <td>Yes
 *     <td>Minus sign
 *   <tr valign=top>
 *     <td><code>,</code>
 *     <td>Number
 *     <td>Yes
 *     <td>Grouping separator
 *   <tr valign=top bgcolor="#eeeeff">
 *     <td><code>E</code>
 *     <td>Number
 *     <td>Yes
 *     <td>Separates mantissa and exponent in scientific notation.
 *         <em>Need not be quoted in prefix or suffix.</em>
 *   <tr valign=top>
 *     <td><code>+</code>
 *     <td>Exponent
 *     <td>Yes
 *     <td>Prefix positive exponents with localized plus sign.
 *         <em>Need not be quoted in prefix or suffix.</em>
 *   <tr valign=top bgcolor="#eeeeff">
 *     <td><code>;</code>
 *     <td>Subpattern boundary
 *     <td>Yes
 *     <td>Separates positive and negative subpatterns
 *   <tr valign=top>
 *     <td><code>\%</code>
 *     <td>Prefix or suffix
 *     <td>Yes
 *     <td>Multiply by 100 and show as percentage
 *   <tr valign=top bgcolor="#eeeeff">
 *     <td><code>\\u2030</code>
 *     <td>Prefix or suffix
 *     <td>Yes
 *     <td>Multiply by 1000 and show as per mille
 *   <tr valign=top>
 *     <td><code>\htmlonly&curren;\endhtmlonly</code> (<code>\\u00A4</code>)
 *     <td>Prefix or suffix
 *     <td>No
 *     <td>Currency sign, replaced by currency symbol.  If
 *         doubled, replaced by international currency symbol.
 *         If tripled, replaced by currency plural names, for example,
 *         "US dollar" or "US dollars" for America.
 *         If present in a pattern, the monetary decimal separator
 *         is used instead of the decimal separator.
 *   <tr valign=top bgcolor="#eeeeff">
 *     <td><code>'</code>
 *     <td>Prefix or suffix
 *     <td>No
 *     <td>Used to quote special characters in a prefix or suffix,
 *         for example, <code>"'#'#"</code> formats 123 to
 *         <code>"#123"</code>.  To create a single quote
 *         itself, use two in a row: <code>"# o''clock"</code>.
 *   <tr valign=top>
 *     <td><code>*</code>
 *     <td>Prefix or suffix boundary
 *     <td>Yes
 *     <td>Pad escape, precedes pad character
 * </table>
 *
 * <p>A DecimalFormat pattern contains a positive and negative
 * subpattern, for example, "#,##0.00;(#,##0.00)".  Each subpattern has a
 * prefix, a numeric part, and a suffix.  If there is no explicit negative
 * subpattern, the negative subpattern is the localized minus sign prefixed to the
 * positive subpattern. That is, "0.00" alone is equivalent to "0.00;-0.00".  If there
 * is an explicit negative subpattern, it serves only to specify the negative
 * prefix and suffix; the number of digits, minimal digits, and other
 * characteristics are ignored in the negative subpattern. That means that
 * "#,##0.0#;(#)" has precisely the same result as "#,##0.0#;(#,##0.0#)".
 *
 * <p>The prefixes, suffixes, and various symbols used for infinity, digits,
 * thousands separators, decimal separators, etc. may be set to arbitrary
 * values, and they will appear properly during formatting.  However, care must
 * be taken that the symbols and strings do not conflict, or parsing will be
 * unreliable.  For example, either the positive and negative prefixes or the
 * suffixes must be distinct for parse() to be able
 * to distinguish positive from negative values.  Another example is that the
 * decimal separator and thousands separator should be distinct characters, or
 * parsing will be impossible.
 *
 * <p>The <em>grouping separator</em> is a character that separates clusters of
 * integer digits to make large numbers more legible.  It commonly used for
 * thousands, but in some locales it separates ten-thousands.  The <em>grouping
 * size</em> is the number of digits between the grouping separators, such as 3
 * for "100,000,000" or 4 for "1 0000 0000". There are actually two different
 * grouping sizes: One used for the least significant integer digits, the
 * <em>primary grouping size</em>, and one used for all others, the
 * <em>secondary grouping size</em>.  In most locales these are the same, but
 * sometimes they are different. For example, if the primary grouping interval
 * is 3, and the secondary is 2, then this corresponds to the pattern
 * "#,##,##0", and the number 123456789 is formatted as "12,34,56,789".  If a
 * pattern contains multiple grouping separators, the interval between the last
 * one and the end of the integer defines the primary grouping size, and the
 * interval between the last two defines the secondary grouping size. All others
 * are ignored, so "#,##,###,####" == "###,###,####" == "##,#,###,####".
 *
 * <p>Illegal patterns, such as "#.#.#" or "#.###,###", will cause
 * DecimalFormat to set a failing UErrorCode.
 *
 * <p><strong>Pattern BNF</strong>
 *
 * <pre>
 * pattern    := subpattern (';' subpattern)?
 * subpattern := prefix? number exponent? suffix?
 * number     := (integer ('.' fraction)?) | sigDigits
 * prefix     := '\\u0000'..'\\uFFFD' - specialCharacters
 * suffix     := '\\u0000'..'\\uFFFD' - specialCharacters
 * integer    := '#'* '0'* '0'
 * fraction   := '0'* '#'*
 * sigDigits  := '#'* '@' '@'* '#'*
 * exponent   := 'E' '+'? '0'* '0'
 * padSpec    := '*' padChar
 * padChar    := '\\u0000'..'\\uFFFD' - quote
 * &nbsp;
 * Notation:
 *   X*       0 or more instances of X
 *   X?       0 or 1 instances of X
 *   X|Y      either X or Y
 *   C..D     any character from C up to D, inclusive
 *   S-T      characters in S, except those in T
 * </pre>
 * The first subpattern is for positive numbers. The second (optional)
 * subpattern is for negative numbers.
 *
 * <p>Not indicated in the BNF syntax above:
 *
 * <ul><li>The grouping separator ',' can occur inside the integer and
 * sigDigits elements, between any two pattern characters of that
 * element, as long as the integer or sigDigits element is not
 * followed by the exponent element.
 *
 * <li>Two grouping intervals are recognized: That between the
 *     decimal point and the first grouping symbol, and that
 *     between the first and second grouping symbols. These
 *     intervals are identical in most locales, but in some
 *     locales they differ. For example, the pattern
 *     &quot;#,##,###&quot; formats the number 123456789 as
 *     &quot;12,34,56,789&quot;.</li>
 *
 * <li>The pad specifier <code>padSpec</code> may appear before the prefix,
 * after the prefix, before the suffix, after the suffix, or not at all.
 *
 * <li>In place of '0', the digits '1' through '9' may be used to
 * indicate a rounding increment.
 * </ul>
 *
 * <p><strong>Parsing</strong>
 *
 * <p>DecimalFormat parses all Unicode characters that represent
 * decimal digits, as defined by u_charDigitValue().  In addition,
 * DecimalFormat also recognizes as digits the ten consecutive
 * characters starting with the localized zero digit defined in the
 * DecimalFormatSymbols object.  During formatting, the
 * DecimalFormatSymbols-based digits are output.
 *
 * <p>During parsing, grouping separators are ignored if in lenient mode;
 * otherwise, if present, they must be in appropriate positions.
 *
 * <p>For currency parsing, the formatter is able to parse every currency
 * style formats no matter which style the formatter is constructed with.
 * For example, a formatter instance gotten from
 * NumberFormat.getInstance(ULocale, NumberFormat.CURRENCYSTYLE) can parse
 * formats such as "USD1.00" and "3.00 US dollars".
 *
 * <p>If parse(UnicodeString&,Formattable&,ParsePosition&)
 * fails to parse a string, it leaves the parse position unchanged.
 * The convenience method parse(UnicodeString&,Formattable&,UErrorCode&)
 * indicates parse failure by setting a failing
 * UErrorCode.
 *
 * <p><strong>Formatting</strong>
 *
 * <p>Formatting is guided by several parameters, all of which can be
 * specified either using a pattern or using the API.  The following
 * description applies to formats that do not use <a href="#sci">scientific
 * notation</a> or <a href="#sigdig">significant digits</a>.
 *
 * <ul><li>If the number of actual integer digits exceeds the
 * <em>maximum integer digits</em>, then only the least significant
 * digits are shown.  For example, 1997 is formatted as "97" if the
 * maximum integer digits is set to 2.
 *
 * <li>If the number of actual integer digits is less than the
 * <em>minimum integer digits</em>, then leading zeros are added.  For
 * example, 1997 is formatted as "01997" if the minimum integer digits
 * is set to 5.
 *
 * <li>If the number of actual fraction digits exceeds the <em>maximum
 * fraction digits</em>, then rounding is performed to the
 * maximum fraction digits.  For example, 0.125 is formatted as "0.12"
 * if the maximum fraction digits is 2.  This behavior can be changed
 * by specifying a rounding increment and/or a rounding mode.
 *
 * <li>If the number of actual fraction digits is less than the
 * <em>minimum fraction digits</em>, then trailing zeros are added.
 * For example, 0.125 is formatted as "0.1250" if the minimum fraction
 * digits is set to 4.
 *
 * <li>Trailing fractional zeros are not displayed if they occur
 * <em>j</em> positions after the decimal, where <em>j</em> is less
 * than the maximum fraction digits. For example, 0.10004 is
 * formatted as "0.1" if the maximum fraction digits is four or less.
 * </ul>
 *
 * <p><strong>Special Values</strong>
 *
 * <p><code>NaN</code> is represented as a single character, typically
 * <code>\\uFFFD</code>.  This character is determined by the
 * DecimalFormatSymbols object.  This is the only value for which
 * the prefixes and suffixes are not used.
 *
 * <p>Infinity is represented as a single character, typically
 * <code>\\u221E</code>, with the positive or negative prefixes and suffixes
 * applied.  The infinity character is determined by the
 * DecimalFormatSymbols object.
 *
 * <a name="sci"><strong>Scientific Notation</strong></a>
 *
 * <p>Numbers in scientific notation are expressed as the product of a mantissa
 * and a power of ten, for example, 1234 can be expressed as 1.234 x 10<sup>3</sup>. The
 * mantissa is typically in the half-open interval [1.0, 10.0) or sometimes [0.0, 1.0),
 * but it need not be.  DecimalFormat supports arbitrary mantissas.
 * DecimalFormat can be instructed to use scientific
 * notation through the API or through the pattern.  In a pattern, the exponent
 * character immediately followed by one or more digit characters indicates
 * scientific notation.  Example: "0.###E0" formats the number 1234 as
 * "1.234E3".
 *
 * <ul>
 * <li>The number of digit characters after the exponent character gives the
 * minimum exponent digit count.  There is no maximum.  Negative exponents are
 * formatted using the localized minus sign, <em>not</em> the prefix and suffix
 * from the pattern.  This allows patterns such as "0.###E0 m/s".  To prefix
 * positive exponents with a localized plus sign, specify '+' between the
 * exponent and the digits: "0.###E+0" will produce formats "1E+1", "1E+0",
 * "1E-1", etc.  (In localized patterns, use the localized plus sign rather than
 * '+'.)
 *
 * <li>The minimum number of integer digits is achieved by adjusting the
 * exponent.  Example: 0.00123 formatted with "00.###E0" yields "12.3E-4".  This
 * only happens if there is no maximum number of integer digits.  If there is a
 * maximum, then the minimum number of integer digits is fixed at one.
 *
 * <li>The maximum number of integer digits, if present, specifies the exponent
 * grouping.  The most common use of this is to generate <em>engineering
 * notation</em>, in which the exponent is a multiple of three, e.g.,
 * "##0.###E0".  The number 12345 is formatted using "##0.####E0" as "12.345E3".
 *
 * <li>When using scientific notation, the formatter controls the
 * digit counts using significant digits logic.  The maximum number of
 * significant digits limits the total number of integer and fraction
 * digits that will be shown in the mantissa; it does not affect
 * parsing.  For example, 12345 formatted with "##0.##E0" is "12.3E3".
 * See the section on significant digits for more details.
 *
 * <li>The number of significant digits shown is determined as
 * follows: If areSignificantDigitsUsed() returns false, then the
 * minimum number of significant digits shown is one, and the maximum
 * number of significant digits shown is the sum of the <em>minimum
 * integer</em> and <em>maximum fraction</em> digits, and is
 * unaffected by the maximum integer digits.  If this sum is zero,
 * then all significant digits are shown.  If
 * areSignificantDigitsUsed() returns true, then the significant digit
 * counts are specified by getMinimumSignificantDigits() and
 * getMaximumSignificantDigits().  In this case, the number of
 * integer digits is fixed at one, and there is no exponent grouping.
 *
 * <li>Exponential patterns may not contain grouping separators.
 * </ul>
 *
 * <a name="sigdig"><strong>Significant Digits</strong></a>
 *
 * <code>DecimalFormat</code> has two ways of controlling how many
 * digits are shows: (a) significant digits counts, or (b) integer and
 * fraction digit counts.  Integer and fraction digit counts are
 * described above.  When a formatter is using significant digits
 * counts, the number of integer and fraction digits is not specified
 * directly, and the formatter settings for these counts are ignored.
 * Instead, the formatter uses however many integer and fraction
 * digits are required to display the specified number of significant
 * digits.  Examples:
 *
 * <table border=0 cellspacing=3 cellpadding=0>
 *   <tr bgcolor="#ccccff">
 *     <td align=left>Pattern
 *     <td align=left>Minimum significant digits
 *     <td align=left>Maximum significant digits
 *     <td align=left>Number
 *     <td align=left>Output of format()
 *   <tr valign=top>
 *     <td><code>\@\@\@</code>
 *     <td>3
 *     <td>3
 *     <td>12345
 *     <td><code>12300</code>
 *   <tr valign=top bgcolor="#eeeeff">
 *     <td><code>\@\@\@</code>
 *     <td>3
 *     <td>3
 *     <td>0.12345
 *     <td><code>0.123</code>
 *   <tr valign=top>
 *     <td><code>\@\@##</code>
 *     <td>2
 *     <td>4
 *     <td>3.14159
 *     <td><code>3.142</code>
 *   <tr valign=top bgcolor="#eeeeff">
 *     <td><code>\@\@##</code>
 *     <td>2
 *     <td>4
 *     <td>1.23004
 *     <td><code>1.23</code>
 * </table>
 *
 * <ul>
 * <li>Significant digit counts may be expressed using patterns that
 * specify a minimum and maximum number of significant digits.  These
 * are indicated by the <code>'@'</code> and <code>'#'</code>
 * characters.  The minimum number of significant digits is the number
 * of <code>'@'</code> characters.  The maximum number of significant
 * digits is the number of <code>'@'</code> characters plus the number
 * of <code>'#'</code> characters following on the right.  For
 * example, the pattern <code>"@@@"</code> indicates exactly 3
 * significant digits.  The pattern <code>"@##"</code> indicates from
 * 1 to 3 significant digits.  Trailing zero digits to the right of
 * the decimal separator are suppressed after the minimum number of
 * significant digits have been shown.  For example, the pattern
 * <code>"@##"</code> formats the number 0.1203 as
 * <code>"0.12"</code>.
 *
 * <li>If a pattern uses significant digits, it may not contain a
 * decimal separator, nor the <code>'0'</code> pattern character.
 * Patterns such as <code>"@00"</code> or <code>"@.###"</code> are
 * disallowed.
 *
 * <li>Any number of <code>'#'</code> characters may be prepended to
 * the left of the leftmost <code>'@'</code> character.  These have no
 * effect on the minimum and maximum significant digits counts, but
 * may be used to position grouping separators.  For example,
 * <code>"#,#@#"</code> indicates a minimum of one significant digits,
 * a maximum of two significant digits, and a grouping size of three.
 *
 * <li>In order to enable significant digits formatting, use a pattern
 * containing the <code>'@'</code> pattern character.  Alternatively,
 * call setSignificantDigitsUsed(true).
 *
 * <li>In order to disable significant digits formatting, use a
 * pattern that does not contain the <code>'@'</code> pattern
 * character. Alternatively, call setSignificantDigitsUsed(false).
 *
 * <li>The number of significant digits has no effect on parsing.
 *
 * <li>Significant digits may be used together with exponential notation. Such
 * patterns are equivalent to a normal exponential pattern with a minimum and
 * maximum integer digit count of one, a minimum fraction digit count of
 * <code>getMinimumSignificantDigits() - 1</code>, and a maximum fraction digit
 * count of <code>getMaximumSignificantDigits() - 1</code>. For example, the
 * pattern <code>"@@###E0"</code> is equivalent to <code>"0.0###E0"</code>.
 *
 * <li>If significant digits are in use, then the integer and fraction
 * digit counts, as set via the API, are ignored.  If significant
 * digits are not in use, then the significant digit counts, as set via
 * the API, are ignored.
 *
 * </ul>
 *
 * <p><strong>Padding</strong>
 *
 * <p>DecimalFormat supports padding the result of
 * format() to a specific width.  Padding may be specified either
 * through the API or through the pattern syntax.  In a pattern the pad escape
 * character, followed by a single pad character, causes padding to be parsed
 * and formatted.  The pad escape character is '*' in unlocalized patterns, and
 * can be localized using DecimalFormatSymbols::setSymbol() with a
 * DecimalFormatSymbols::kPadEscapeSymbol
 * selector.  For example, <code>"$*x#,##0.00"</code> formats 123 to
 * <code>"$xx123.00"</code>, and 1234 to <code>"$1,234.00"</code>.
 *
 * <ul>
 * <li>When padding is in effect, the width of the positive subpattern,
 * including prefix and suffix, determines the format width.  For example, in
 * the pattern <code>"* #0 o''clock"</code>, the format width is 10.
 *
 * <li>The width is counted in 16-bit code units (char16_ts).
 *
 * <li>Some parameters which usually do not matter have meaning when padding is
 * used, because the pattern width is significant with padding.  In the pattern
 * "* ##,##,#,##0.##", the format width is 14.  The initial characters "##,##,"
 * do not affect the grouping size or maximum integer digits, but they do affect
 * the format width.
 *
 * <li>Padding may be inserted at one of four locations: before the prefix,
 * after the prefix, before the suffix, or after the suffix.  If padding is
 * specified in any other location, applyPattern()
 * sets a failing UErrorCode.  If there is no prefix,
 * before the prefix and after the prefix are equivalent, likewise for the
 * suffix.
 *
 * <li>When specified in a pattern, the 32-bit code point immediately
 * following the pad escape is the pad character. This may be any character,
 * including a special pattern character. That is, the pad escape
 * <em>escapes</em> the following character. If there is no character after
 * the pad escape, then the pattern is illegal.
 *
 * </ul>
 *
 * <p><strong>Rounding</strong>
 *
 * <p>DecimalFormat supports rounding to a specific increment.  For
 * example, 1230 rounded to the nearest 50 is 1250.  1.234 rounded to the
 * nearest 0.65 is 1.3.  The rounding increment may be specified through the API
 * or in a pattern.  To specify a rounding increment in a pattern, include the
 * increment in the pattern itself.  "#,#50" specifies a rounding increment of
 * 50.  "#,##0.05" specifies a rounding increment of 0.05.
 *
 * <p>In the absence of an explicit rounding increment numbers are
 * rounded to their formatted width.
 *
 * <ul>
 * <li>Rounding only affects the string produced by formatting.  It does
 * not affect parsing or change any numerical values.
 *
 * <li>A <em>rounding mode</em> determines how values are rounded; see
 * DecimalFormat::ERoundingMode.  The default rounding mode is
 * DecimalFormat::kRoundHalfEven.  The rounding mode can only be set
 * through the API; it can not be set with a pattern.
 *
 * <li>Some locales use rounding in their currency formats to reflect the
 * smallest currency denomination.
 *
 * <li>In a pattern, digits '1' through '9' specify rounding, but otherwise
 * behave identically to digit '0'.
 * </ul>
 *
 * <p><strong>Synchronization</strong>
 *
 * <p>DecimalFormat objects are not synchronized.  Multiple
 * threads should not access one formatter concurrently.
 *
 * <p><strong>Subclassing</strong>
 *
 * <p><em>User subclasses are not supported.</em> While clients may write
 * subclasses, such code will not necessarily work and will not be
 * guaranteed to work stably from release to release.
 */
class U_I18N_API DecimalFormat : public NumberFormat {
  public:
    /**
     * Pad position.
     * @stable ICU 2.4
     */
    enum EPadPosition {
        kPadBeforePrefix, kPadAfterPrefix, kPadBeforeSuffix, kPadAfterSuffix
    };

    /**
     * Create a DecimalFormat using the default pattern and symbols
     * for the default locale. This is a convenient way to obtain a
     * DecimalFormat when internationalization is not the main concern.
     * <P>
     * To obtain standard formats for a given locale, use the factory methods
     * on NumberFormat such as createInstance. These factories will
     * return the most appropriate sub-class of NumberFormat for a given
     * locale.
     * <p>
     * <strong>NOTE:</strong> New users are strongly encouraged to use
     * #icu::number::NumberFormatter instead of DecimalFormat.
     * @param status    Output param set to success/failure code. If the
     *                  pattern is invalid this will be set to a failure code.
     * @stable ICU 2.0
     */
    DecimalFormat(UErrorCode& status);

    /**
     * Create a DecimalFormat from the given pattern and the symbols
     * for the default locale. This is a convenient way to obtain a
     * DecimalFormat when internationalization is not the main concern.
     * <P>
     * To obtain standard formats for a given locale, use the factory methods
     * on NumberFormat such as createInstance. These factories will
     * return the most appropriate sub-class of NumberFormat for a given
     * locale.
     * <p>
     * <strong>NOTE:</strong> New users are strongly encouraged to use
     * #icu::number::NumberFormatter instead of DecimalFormat.
     * @param pattern   A non-localized pattern string.
     * @param status    Output param set to success/failure code. If the
     *                  pattern is invalid this will be set to a failure code.
     * @stable ICU 2.0
     */
    DecimalFormat(const UnicodeString& pattern, UErrorCode& status);

    /**
     * Create a DecimalFormat from the given pattern and symbols.
     * Use this constructor when you need to completely customize the
     * behavior of the format.
     * <P>
     * To obtain standard formats for a given
     * locale, use the factory methods on NumberFormat such as
     * createInstance or createCurrencyInstance. If you need only minor adjustments
     * to a standard format, you can modify the format returned by
     * a NumberFormat factory method.
     * <p>
     * <strong>NOTE:</strong> New users are strongly encouraged to use
     * #icu::number::NumberFormatter instead of DecimalFormat.
     *
     * @param pattern           a non-localized pattern string
     * @param symbolsToAdopt    the set of symbols to be used.  The caller should not
     *                          delete this object after making this call.
     * @param status            Output param set to success/failure code. If the
     *                          pattern is invalid this will be set to a failure code.
     * @stable ICU 2.0
     */
    DecimalFormat(const UnicodeString& pattern, DecimalFormatSymbols* symbolsToAdopt, UErrorCode& status);

#ifndef U_HIDE_INTERNAL_API

    /**
     * This API is for ICU use only.
     * Create a DecimalFormat from the given pattern, symbols, and style.
     *
     * @param pattern           a non-localized pattern string
     * @param symbolsToAdopt    the set of symbols to be used.  The caller should not
     *                          delete this object after making this call.
     * @param style             style of decimal format
     * @param status            Output param set to success/failure code. If the
     *                          pattern is invalid this will be set to a failure code.
     * @internal
     */
    DecimalFormat(const UnicodeString& pattern, DecimalFormatSymbols* symbolsToAdopt,
                  UNumberFormatStyle style, UErrorCode& status);

#if UCONFIG_HAVE_PARSEALLINPUT

    /**
     * @internal
     */
    void setParseAllInput(UNumberFormatAttributeValue value);

#endif

#endif  /* U_HIDE_INTERNAL_API */

  private:

    /**
     * Internal constructor for DecimalFormat; sets up internal fields. All public constructors should
     * call this constructor.
     */
    DecimalFormat(const DecimalFormatSymbols* symbolsToAdopt, UErrorCode& status);

  public:

    /**
     * Set an integer attribute on this DecimalFormat.
     * May return U_UNSUPPORTED_ERROR if this instance does not support
     * the specified attribute.
     * @param attr the attribute to set
     * @param newValue new value
     * @param status the error type
     * @return *this - for chaining (example: format.setAttribute(...).setAttribute(...) )
     * @stable ICU 51
     */
    virtual DecimalFormat& setAttribute(UNumberFormatAttribute attr, int32_t newValue, UErrorCode& status);

    /**
     * Get an integer
     * May return U_UNSUPPORTED_ERROR if this instance does not support
     * the specified attribute.
     * @param attr the attribute to set
     * @param status the error type
     * @return the attribute value. Undefined if there is an error.
     * @stable ICU 51
     */
    virtual int32_t getAttribute(UNumberFormatAttribute attr, UErrorCode& status) const;


    /**
     * Set whether or not grouping will be used in this format.
     * @param newValue    True, grouping will be used in this format.
     * @see getGroupingUsed
     * @stable ICU 53
     */
    void setGroupingUsed(UBool newValue) override;

    /**
     * Sets whether or not numbers should be parsed as integers only.
     * @param value    set True, this format will parse numbers as integers
     *                 only.
     * @see isParseIntegerOnly
     * @stable ICU 53
     */
    void setParseIntegerOnly(UBool value) override;

    /**
     * Sets whether lenient parsing should be enabled (it is off by default).
     *
     * @param enable \c true if lenient parsing should be used,
     *               \c false otherwise.
     * @stable ICU 4.8
     */
    void setLenient(UBool enable) override;

    /**
     * Create a DecimalFormat from the given pattern and symbols.
     * Use this constructor when you need to completely customize the
     * behavior of the format.
     * <P>
     * To obtain standard formats for a given
     * locale, use the factory methods on NumberFormat such as
     * createInstance or createCurrencyInstance. If you need only minor adjustments
     * to a standard format, you can modify the format returned by
     * a NumberFormat factory method.
     * <p>
     * <strong>NOTE:</strong> New users are strongly encouraged to use
     * #icu::number::NumberFormatter instead of DecimalFormat.
     *
     * @param pattern           a non-localized pattern string
     * @param symbolsToAdopt    the set of symbols to be used.  The caller should not
     *                          delete this object after making this call.
     * @param parseError        Output param to receive errors occurred during parsing
     * @param status            Output param set to success/failure code. If the
     *                          pattern is invalid this will be set to a failure code.
     * @stable ICU 2.0
     */
    DecimalFormat(const UnicodeString& pattern, DecimalFormatSymbols* symbolsToAdopt,
                  UParseError& parseError, UErrorCode& status);

    /**
     * Create a DecimalFormat from the given pattern and symbols.
     * Use this constructor when you need to completely customize the
     * behavior of the format.
     * <P>
     * To obtain standard formats for a given
     * locale, use the factory methods on NumberFormat such as
     * createInstance or createCurrencyInstance. If you need only minor adjustments
     * to a standard format, you can modify the format returned by
     * a NumberFormat factory method.
     * <p>
     * <strong>NOTE:</strong> New users are strongly encouraged to use
     * #icu::number::NumberFormatter instead of DecimalFormat.
     *
     * @param pattern           a non-localized pattern string
     * @param symbols   the set of symbols to be used
     * @param status            Output param set to success/failure code. If the
     *                          pattern is invalid this will be set to a failure code.
     * @stable ICU 2.0
     */
    DecimalFormat(const UnicodeString& pattern, const DecimalFormatSymbols& symbols, UErrorCode& status);

    /**
     * Copy constructor.
     *
     * @param source    the DecimalFormat object to be copied from.
     * @stable ICU 2.0
     */
    DecimalFormat(const DecimalFormat& source);

    /**
     * Assignment operator.
     *
     * @param rhs    the DecimalFormat object to be copied.
     * @stable ICU 2.0
     */
    DecimalFormat& operator=(const DecimalFormat& rhs);

    /**
     * Destructor.
     * @stable ICU 2.0
     */
    ~DecimalFormat() override;

    /**
     * Clone this Format object polymorphically. The caller owns the
     * result and should delete it when done.
     *
     * @return    a polymorphic copy of this DecimalFormat.
     * @stable ICU 2.0
     */
    DecimalFormat* clone() const override;

    /**
     * Return true if the given Format objects are semantically equal.
     * Objects of different subclasses are considered unequal.
     *
     * @param other    the object to be compared with.
     * @return         true if the given Format objects are semantically equal.
     * @stable ICU 2.0
     */
    bool operator==(const Format& other) const override;


    using NumberFormat::format;

    /**
     * Format a double or long number using base-10 representation.
     *
     * @param number    The value to be formatted.
     * @param appendTo  Output parameter to receive result.
     *                  Result is appended to existing contents.
     * @param pos       On input: an alignment field, if desired.
     *                  On output: the offsets of the alignment field.
     * @return          Reference to 'appendTo' parameter.
     * @stable ICU 2.0
     */
    UnicodeString& format(double number, UnicodeString& appendTo, FieldPosition& pos) const override;

#ifndef U_HIDE_INTERNAL_API
    /**
     * Format a double or long number using base-10 representation.
     *
     * @param number    The value to be formatted.
     * @param appendTo  Output parameter to receive result.
     *                  Result is appended to existing contents.
     * @param pos       On input: an alignment field, if desired.
     *                  On output: the offsets of the alignment field.
     * @param status
     * @return          Reference to 'appendTo' parameter.
     * @internal
     */
    UnicodeString& format(double number, UnicodeString& appendTo, FieldPosition& pos,
                          UErrorCode& status) const override;
#endif  /* U_HIDE_INTERNAL_API */

    /**
     * Format a double or long number using base-10 representation.
     *
     * @param number    The value to be formatted.
     * @param appendTo  Output parameter to receive result.
     *                  Result is appended to existing contents.
     * @param posIter   On return, can be used to iterate over positions
     *                  of fields generated by this format call.
     *                  Can be nullptr.
     * @param status    Output param filled with success/failure status.
     * @return          Reference to 'appendTo' parameter.
     * @stable ICU 4.4
     */
    UnicodeString& format(double number, UnicodeString& appendTo, FieldPositionIterator* posIter,
                          UErrorCode& status) const override;

    /**
     * Format a long number using base-10 representation.
     *
     * @param number    The value to be formatted.
     * @param appendTo  Output parameter to receive result.
     *                  Result is appended to existing contents.
     * @param pos       On input: an alignment field, if desired.
     *                  On output: the offsets of the alignment field.
     * @return          Reference to 'appendTo' parameter.
     * @stable ICU 2.0
     */
    UnicodeString& format(int32_t number, UnicodeString& appendTo, FieldPosition& pos) const override;

#ifndef U_HIDE_INTERNAL_API
    /**
     * Format a long number using base-10 representation.
     *
     * @param number    The value to be formatted.
     * @param appendTo  Output parameter to receive result.
     *                  Result is appended to existing contents.
     * @param pos       On input: an alignment field, if desired.
     *                  On output: the offsets of the alignment field.
     * @param status    Output param filled with success/failure status.
     * @return          Reference to 'appendTo' parameter.
     * @internal
     */
    UnicodeString& format(int32_t number, UnicodeString& appendTo, FieldPosition& pos,
                          UErrorCode& status) const override;
#endif  /* U_HIDE_INTERNAL_API */

    /**
     * Format a long number using base-10 representation.
     *
     * @param number    The value to be formatted.
     * @param appendTo  Output parameter to receive result.
     *                  Result is appended to existing contents.
     * @param posIter   On return, can be used to iterate over positions
     *                  of fields generated by this format call.
     *                  Can be nullptr.
     * @param status    Output param filled with success/failure status.
     * @return          Reference to 'appendTo' parameter.
     * @stable ICU 4.4
     */
    UnicodeString& format(int32_t number, UnicodeString& appendTo, FieldPositionIterator* posIter,
                          UErrorCode& status) const override;

    /**
     * Format an int64 number using base-10 representation.
     *
     * @param number    The value to be formatted.
     * @param appendTo  Output parameter to receive result.
     *                  Result is appended to existing contents.
     * @param pos       On input: an alignment field, if desired.
     *                  On output: the offsets of the alignment field.
     * @return          Reference to 'appendTo' parameter.
     * @stable ICU 2.8
     */
    UnicodeString& format(int64_t number, UnicodeString& appendTo, FieldPosition& pos) const override;

#ifndef U_HIDE_INTERNAL_API
    /**
     * Format an int64 number using base-10 representation.
     *
     * @param number    The value to be formatted.
     * @param appendTo  Output parameter to receive result.
     *                  Result is appended to existing contents.
     * @param pos       On input: an alignment field, if desired.
     *                  On output: the offsets of the alignment field.
     * @param status    Output param filled with success/failure status.
     * @return          Reference to 'appendTo' parameter.
     * @internal
     */
    UnicodeString& format(int64_t number, UnicodeString& appendTo, FieldPosition& pos,
                          UErrorCode& status) const override;
#endif  /* U_HIDE_INTERNAL_API */

    /**
     * Format an int64 number using base-10 representation.
     *
     * @param number    The value to be formatted.
     * @param appendTo  Output parameter to receive result.
     *                  Result is appended to existing contents.
     * @param posIter   On return, can be used to iterate over positions
     *                  of fields generated by this format call.
     *                  Can be nullptr.
     * @param status    Output param filled with success/failure status.
     * @return          Reference to 'appendTo' parameter.
     * @stable ICU 4.4
     */
    UnicodeString& format(int64_t number, UnicodeString& appendTo, FieldPositionIterator* posIter,
                          UErrorCode& status) const override;

    /**
     * Format a decimal number.
     * The syntax of the unformatted number is a "numeric string"
     * as defined in the Decimal Arithmetic Specification, available at
     * http://speleotrove.com/decimal
     *
     * @param number    The unformatted number, as a string.
     * @param appendTo  Output parameter to receive result.
     *                  Result is appended to existing contents.
     * @param posIter   On return, can be used to iterate over positions
     *                  of fields generated by this format call.
     *                  Can be nullptr.
     * @param status    Output param filled with success/failure status.
     * @return          Reference to 'appendTo' parameter.
     * @stable ICU 4.4
     */
    UnicodeString& format(StringPiece number, UnicodeString& appendTo, FieldPositionIterator* posIter,
                          UErrorCode& status) const override;

#ifndef U_HIDE_INTERNAL_API

    /**
     * Format a decimal number.
     * The number is a DecimalQuantity wrapper onto a floating point decimal number.
     * The default implementation in NumberFormat converts the decimal number
     * to a double and formats that.
     *
     * @param number    The number, a DecimalQuantity format Decimal Floating Point.
     * @param appendTo  Output parameter to receive result.
     *                  Result is appended to existing contents.
     * @param posIter   On return, can be used to iterate over positions
     *                  of fields generated by this format call.
     * @param status    Output param filled with success/failure status.
     * @return          Reference to 'appendTo' parameter.
     * @internal
     */
    UnicodeString& format(const number::impl::DecimalQuantity& number, UnicodeString& appendTo,
                          FieldPositionIterator* posIter, UErrorCode& status) const override;

    /**
     * Format a decimal number.
     * The number is a DecimalQuantity wrapper onto a floating point decimal number.
     * The default implementation in NumberFormat converts the decimal number
     * to a double and formats that.
     *
     * @param number    The number, a DecimalQuantity format Decimal Floating Point.
     * @param appendTo  Output parameter to receive result.
     *                  Result is appended to existing contents.
     * @param pos       On input: an alignment field, if desired.
     *                  On output: the offsets of the alignment field.
     * @param status    Output param filled with success/failure status.
     * @return          Reference to 'appendTo' parameter.
     * @internal
     */
    UnicodeString& format(const number::impl::DecimalQuantity& number, UnicodeString& appendTo,
                          FieldPosition& pos, UErrorCode& status) const override;

#endif // U_HIDE_INTERNAL_API

    using NumberFormat::parse;

    /**
     * Parse the given string using this object's choices. The method
     * does string comparisons to try to find an optimal match.
     * If no object can be parsed, index is unchanged, and nullptr is
     * returned.  The result is returned as the most parsimonious
     * type of Formattable that will accommodate all of the
     * necessary precision.  For example, if the result is exactly 12,
     * it will be returned as a long.  However, if it is 1.5, it will
     * be returned as a double.
     *
     * @param text           The text to be parsed.
     * @param result         Formattable to be set to the parse result.
     *                       If parse fails, return contents are undefined.
     * @param parsePosition  The position to start parsing at on input.
     *                       On output, moved to after the last successfully
     *                       parse character. On parse failure, does not change.
     * @see Formattable
     * @stable ICU 2.0
     */
    void parse(const UnicodeString& text, Formattable& result,
               ParsePosition& parsePosition) const override;

    /**
     * Parses text from the given string as a currency amount.  Unlike
     * the parse() method, this method will attempt to parse a generic
     * currency name, searching for a match of this object's locale's
     * currency display names, or for a 3-letter ISO currency code.
     * This method will fail if this format is not a currency format,
     * that is, if it does not contain the currency pattern symbol
     * (U+00A4) in its prefix or suffix.
     *
     * @param text the string to parse
     * @param pos  input-output position; on input, the position within text
     *             to match; must have 0 <= pos.getIndex() < text.length();
     *             on output, the position after the last matched character.
     *             If the parse fails, the position in unchanged upon output.
     * @return     if parse succeeds, a pointer to a newly-created CurrencyAmount
     *             object (owned by the caller) containing information about
     *             the parsed currency; if parse fails, this is nullptr.
     * @stable ICU 49
     */
    CurrencyAmount* parseCurrency(const UnicodeString& text, ParsePosition& pos) const override;

    /**
     * Returns the decimal format symbols, which is generally not changed
     * by the programmer or user.
     * @return desired DecimalFormatSymbols
     * @see DecimalFormatSymbols
     * @stable ICU 2.0
     */
    virtual const DecimalFormatSymbols* getDecimalFormatSymbols() const;

    /**
     * Sets the decimal format symbols, which is generally not changed
     * by the programmer or user.
     * @param symbolsToAdopt DecimalFormatSymbols to be adopted.
     * @stable ICU 2.0
     */
    virtual void adoptDecimalFormatSymbols(DecimalFormatSymbols* symbolsToAdopt);

    /**
     * Sets the decimal format symbols, which is generally not changed
     * by the programmer or user.
     * @param symbols DecimalFormatSymbols.
     * @stable ICU 2.0
     */
    virtual void setDecimalFormatSymbols(const DecimalFormatSymbols& symbols);


    /**
     * Returns the currency plural format information,
     * which is generally not changed by the programmer or user.
     * @return desired CurrencyPluralInfo
     * @stable ICU 4.2
     */
    virtual const CurrencyPluralInfo* getCurrencyPluralInfo() const;

    /**
     * Sets the currency plural format information,
     * which is generally not changed by the programmer or user.
     * @param toAdopt CurrencyPluralInfo to be adopted.
     * @stable ICU 4.2
     */
    virtual void adoptCurrencyPluralInfo(CurrencyPluralInfo* toAdopt);

    /**
     * Sets the currency plural format information,
     * which is generally not changed by the programmer or user.
     * @param info Currency Plural Info.
     * @stable ICU 4.2
     */
    virtual void setCurrencyPluralInfo(const CurrencyPluralInfo& info);


    /**
     * Get the positive prefix.
     *
     * @param result    Output param which will receive the positive prefix.
     * @return          A reference to 'result'.
     * Examples: +123, $123, sFr123
     * @stable ICU 2.0
     */
    UnicodeString& getPositivePrefix(UnicodeString& result) const;

    /**
     * Set the positive prefix.
     *
     * @param newValue    the new value of the the positive prefix to be set.
     * Examples: +123, $123, sFr123
     * @stable ICU 2.0
     */
    virtual void setPositivePrefix(const UnicodeString& newValue);

    /**
     * Get the negative prefix.
     *
     * @param result    Output param which will receive the negative prefix.
     * @return          A reference to 'result'.
     * Examples: -123, ($123) (with negative suffix), sFr-123
     * @stable ICU 2.0
     */
    UnicodeString& getNegativePrefix(UnicodeString& result) const;

    /**
     * Set the negative prefix.
     *
     * @param newValue    the new value of the the negative prefix to be set.
     * Examples: -123, ($123) (with negative suffix), sFr-123
     * @stable ICU 2.0
     */
    virtual void setNegativePrefix(const UnicodeString& newValue);

    /**
     * Get the positive suffix.
     *
     * @param result    Output param which will receive the positive suffix.
     * @return          A reference to 'result'.
     * Example: 123%
     * @stable ICU 2.0
     */
    UnicodeString& getPositiveSuffix(UnicodeString& result) const;

    /**
     * Set the positive suffix.
     *
     * @param newValue    the new value of the positive suffix to be set.
     * Example: 123%
     * @stable ICU 2.0
     */
    virtual void setPositiveSuffix(const UnicodeString& newValue);

    /**
     * Get the negative suffix.
     *
     * @param result    Output param which will receive the negative suffix.
     * @return          A reference to 'result'.
     * Examples: -123%, ($123) (with positive suffixes)
     * @stable ICU 2.0
     */
    UnicodeString& getNegativeSuffix(UnicodeString& result) const;

    /**
     * Set the negative suffix.
     *
     * @param newValue    the new value of the negative suffix to be set.
     * Examples: 123%
     * @stable ICU 2.0
     */
    virtual void setNegativeSuffix(const UnicodeString& newValue);

    /**
     * Whether to show the plus sign on positive (non-negative) numbers; for example, "+12"
     *
     * For more control over sign display, use NumberFormatter.
     *
     * @return Whether the sign is shown on positive numbers and zero.
     * @stable ICU 64
     */
    UBool isSignAlwaysShown() const;

    /**
     * Set whether to show the plus sign on positive (non-negative) numbers; for example, "+12".
     *
     * For more control over sign display, use NumberFormatter.
     *
     * @param value true to always show a sign; false to hide the sign on positive numbers and zero.
     * @stable ICU 64
     */
    void setSignAlwaysShown(UBool value);

    /**
     * Get the multiplier for use in percent, permill, etc.
     * For a percentage, set the suffixes to have "%" and the multiplier to be 100.
     * (For Arabic, use arabic percent symbol).
     * For a permill, set the suffixes to have "\\u2031" and the multiplier to be 1000.
     *
     * The number may also be multiplied by a power of ten; see getMultiplierScale().
     *
     * @return    the multiplier for use in percent, permill, etc.
     * Examples: with 100, 1.23 -> "123", and "123" -> 1.23
     * @stable ICU 2.0
     */
    int32_t getMultiplier() const;

    /**
     * Set the multiplier for use in percent, permill, etc.
     * For a percentage, set the suffixes to have "%" and the multiplier to be 100.
     * (For Arabic, use arabic percent symbol).
     * For a permill, set the suffixes to have "\\u2031" and the multiplier to be 1000.
     *
     * This method only supports integer multipliers. To multiply by a non-integer, pair this
     * method with setMultiplierScale().
     *
     * @param newValue    the new value of the multiplier for use in percent, permill, etc.
     * Examples: with 100, 1.23 -> "123", and "123" -> 1.23
     * @stable ICU 2.0
     */
    virtual void setMultiplier(int32_t newValue);

    /**
     * Gets the power of ten by which number should be multiplied before formatting, which
     * can be combined with setMultiplier() to multiply by any arbitrary decimal value.
     *
     * A multiplier scale of 2 corresponds to multiplication by 100, and a multiplier scale
     * of -2 corresponds to multiplication by 0.01.
     *
     * This method is analogous to UNUM_SCALE in getAttribute.
     *
     * @return    the current value of the power-of-ten multiplier.
     * @stable ICU 62
     */
    int32_t getMultiplierScale() const;

    /**
     * Sets a power of ten by which number should be multiplied before formatting, which
     * can be combined with setMultiplier() to multiply by any arbitrary decimal value.
     *
     * A multiplier scale of 2 corresponds to multiplication by 100, and a multiplier scale
     * of -2 corresponds to multiplication by 0.01.
     *
     * For example, to multiply numbers by 0.5 before formatting, you can do:
     *
     * <pre>
     * df.setMultiplier(5);
     * df.setMultiplierScale(-1);
     * </pre>
     *
     * This method is analogous to UNUM_SCALE in setAttribute.
     *
     * @param newValue    the new value of the power-of-ten multiplier.
     * @stable ICU 62
     */
    void setMultiplierScale(int32_t newValue);

    /**
     * Get the rounding increment.
     * @return A positive rounding increment, or 0.0 if a custom rounding
     * increment is not in effect.
     * @see #setRoundingIncrement
     * @see #getRoundingMode
     * @see #setRoundingMode
     * @stable ICU 2.0
     */
    virtual double getRoundingIncrement() const;

    /**
     * Set the rounding increment.  In the absence of a rounding increment,
     *    numbers will be rounded to the number of digits displayed.
     * @param newValue A positive rounding increment, or 0.0 to
     * use the default rounding increment.
     * Negative increments are equivalent to 0.0.
     * @see #getRoundingIncrement
     * @see #getRoundingMode
     * @see #setRoundingMode
     * @stable ICU 2.0
     */
    virtual void setRoundingIncrement(double newValue);

    /**
     * Get the rounding mode.
     * @return A rounding mode
     * @see #setRoundingIncrement
     * @see #getRoundingIncrement
     * @see #setRoundingMode
     * @stable ICU 2.0
     */
    virtual ERoundingMode getRoundingMode() const override;

    /**
     * Set the rounding mode.
     * @param roundingMode A rounding mode
     * @see #setRoundingIncrement
     * @see #getRoundingIncrement
     * @see #getRoundingMode
     * @stable ICU 2.0
     */
    virtual void setRoundingMode(ERoundingMode roundingMode) override;

    /**
     * Get the width to which the output of format() is padded.
     * The width is counted in 16-bit code units.
     * @return the format width, or zero if no padding is in effect
     * @see #setFormatWidth
     * @see #getPadCharacterString
     * @see #setPadCharacter
     * @see #getPadPosition
     * @see #setPadPosition
     * @stable ICU 2.0
     */
    virtual int32_t getFormatWidth() const;

    /**
     * Set the width to which the output of format() is padded.
     * The width is counted in 16-bit code units.
     * This method also controls whether padding is enabled.
     * @param width the width to which to pad the result of
     * format(), or zero to disable padding.  A negative
     * width is equivalent to 0.
     * @see #getFormatWidth
     * @see #getPadCharacterString
     * @see #setPadCharacter
     * @see #getPadPosition
     * @see #setPadPosition
     * @stable ICU 2.0
     */
    virtual void setFormatWidth(int32_t width);

    /**
     * Get the pad character used to pad to the format width.  The
     * default is ' '.
     * @return a string containing the pad character. This will always
     * have a length of one 32-bit code point.
     * @see #setFormatWidth
     * @see #getFormatWidth
     * @see #setPadCharacter
     * @see #getPadPosition
     * @see #setPadPosition
     * @stable ICU 2.0
     */
    virtual UnicodeString getPadCharacterString() const;

    /**
     * Set the character used to pad to the format width.  If padding
     * is not enabled, then this will take effect if padding is later
     * enabled.
     * @param padChar a string containing the pad character. If the string
     * has length 0, then the pad character is set to ' '.  Otherwise
     * padChar.char32At(0) will be used as the pad character.
     * @see #setFormatWidth
     * @see #getFormatWidth
     * @see #getPadCharacterString
     * @see #getPadPosition
     * @see #setPadPosition
     * @stable ICU 2.0
     */
    virtual void setPadCharacter(const UnicodeString& padChar);

    /**
     * Get the position at which padding will take place.  This is the location
     * at which padding will be inserted if the result of format()
     * is shorter than the format width.
     * @return the pad position, one of kPadBeforePrefix,
     * kPadAfterPrefix, kPadBeforeSuffix, or
     * kPadAfterSuffix.
     * @see #setFormatWidth
     * @see #getFormatWidth
     * @see #setPadCharacter
     * @see #getPadCharacterString
     * @see #setPadPosition
     * @see #EPadPosition
     * @stable ICU 2.0
     */
    virtual EPadPosition getPadPosition() const;

    /**
     * Set the position at which padding will take place.  This is the location
     * at which padding will be inserted if the result of format()
     * is shorter than the format width.  This has no effect unless padding is
     * enabled.
     * @param padPos the pad position, one of kPadBeforePrefix,
     * kPadAfterPrefix, kPadBeforeSuffix, or
     * kPadAfterSuffix.
     * @see #setFormatWidth
     * @see #getFormatWidth
     * @see #setPadCharacter
     * @see #getPadCharacterString
     * @see #getPadPosition
     * @see #EPadPosition
     * @stable ICU 2.0
     */
    virtual void setPadPosition(EPadPosition padPos);

    /**
     * Return whether or not scientific notation is used.
     * @return true if this object formats and parses scientific notation
     * @see #setScientificNotation
     * @see #getMinimumExponentDigits
     * @see #setMinimumExponentDigits
     * @see #isExponentSignAlwaysShown
     * @see #setExponentSignAlwaysShown
     * @stable ICU 2.0
     */
    virtual UBool isScientificNotation() const;

    /**
     * Set whether or not scientific notation is used. When scientific notation
     * is used, the effective maximum number of integer digits is <= 8.  If the
     * maximum number of integer digits is set to more than 8, the effective
     * maximum will be 1.  This allows this call to generate a 'default' scientific
     * number format without additional changes.
     * @param useScientific true if this object formats and parses scientific
     * notation
     * @see #isScientificNotation
     * @see #getMinimumExponentDigits
     * @see #setMinimumExponentDigits
     * @see #isExponentSignAlwaysShown
     * @see #setExponentSignAlwaysShown
     * @stable ICU 2.0
     */
    virtual void setScientificNotation(UBool useScientific);

    /**
     * Return the minimum exponent digits that will be shown.
     * @return the minimum exponent digits that will be shown
     * @see #setScientificNotation
     * @see #isScientificNotation
     * @see #setMinimumExponentDigits
     * @see #isExponentSignAlwaysShown
     * @see #setExponentSignAlwaysShown
     * @stable ICU 2.0
     */
    virtual int8_t getMinimumExponentDigits() const;

    /**
     * Set the minimum exponent digits that will be shown.  This has no
     * effect unless scientific notation is in use.
     * @param minExpDig a value >= 1 indicating the fewest exponent digits
     * that will be shown.  Values less than 1 will be treated as 1.
     * @see #setScientificNotation
     * @see #isScientificNotation
     * @see #getMinimumExponentDigits
     * @see #isExponentSignAlwaysShown
     * @see #setExponentSignAlwaysShown
     * @stable ICU 2.0
     */
    virtual void setMinimumExponentDigits(int8_t minExpDig);

    /**
     * Return whether the exponent sign is always shown.
     * @return true if the exponent is always prefixed with either the
     * localized minus sign or the localized plus sign, false if only negative
     * exponents are prefixed with the localized minus sign.
     * @see #setScientificNotation
     * @see #isScientificNotation
     * @see #setMinimumExponentDigits
     * @see #getMinimumExponentDigits
     * @see #setExponentSignAlwaysShown
     * @stable ICU 2.0
     */
    virtual UBool isExponentSignAlwaysShown() const;

    /**
     * Set whether the exponent sign is always shown.  This has no effect
     * unless scientific notation is in use.
     * @param expSignAlways true if the exponent is always prefixed with either
     * the localized minus sign or the localized plus sign, false if only
     * negative exponents are prefixed with the localized minus sign.
     * @see #setScientificNotation
     * @see #isScientificNotation
     * @see #setMinimumExponentDigits
     * @see #getMinimumExponentDigits
     * @see #isExponentSignAlwaysShown
     * @stable ICU 2.0
     */
    virtual void setExponentSignAlwaysShown(UBool expSignAlways);

    /**
     * Return the grouping size. Grouping size is the number of digits between
     * grouping separators in the integer portion of a number.  For example,
     * in the number "123,456.78", the grouping size is 3.
     *
     * @return    the grouping size.
     * @see setGroupingSize
     * @see NumberFormat::isGroupingUsed
     * @see DecimalFormatSymbols::getGroupingSeparator
     * @stable ICU 2.0
     */
    int32_t getGroupingSize() const;

    /**
     * Set the grouping size. Grouping size is the number of digits between
     * grouping separators in the integer portion of a number.  For example,
     * in the number "123,456.78", the grouping size is 3.
     *
     * @param newValue    the new value of the grouping size.
     * @see getGroupingSize
     * @see NumberFormat::setGroupingUsed
     * @see DecimalFormatSymbols::setGroupingSeparator
     * @stable ICU 2.0
     */
    virtual void setGroupingSize(int32_t newValue);

    /**
     * Return the secondary grouping size. In some locales one
     * grouping interval is used for the least significant integer
     * digits (the primary grouping size), and another is used for all
     * others (the secondary grouping size).  A formatter supporting a
     * secondary grouping size will return a positive integer unequal
     * to the primary grouping size returned by
     * getGroupingSize().  For example, if the primary
     * grouping size is 4, and the secondary grouping size is 2, then
     * the number 123456789 formats as "1,23,45,6789", and the pattern
     * appears as "#,##,###0".
     * @return the secondary grouping size, or a value less than
     * one if there is none
     * @see setSecondaryGroupingSize
     * @see NumberFormat::isGroupingUsed
     * @see DecimalFormatSymbols::getGroupingSeparator
     * @stable ICU 2.4
     */
    int32_t getSecondaryGroupingSize() const;

    /**
     * Set the secondary grouping size. If set to a value less than 1,
     * then secondary grouping is turned off, and the primary grouping
     * size is used for all intervals, not just the least significant.
     *
     * @param newValue    the new value of the secondary grouping size.
     * @see getSecondaryGroupingSize
     * @see NumberFormat#setGroupingUsed
     * @see DecimalFormatSymbols::setGroupingSeparator
     * @stable ICU 2.4
     */
    virtual void setSecondaryGroupingSize(int32_t newValue);

    /**
     * Returns the minimum number of grouping digits.
     * Grouping separators are output if there are at least this many
     * digits to the left of the first (rightmost) grouping separator,
     * that is, there are at least (minimum grouping + grouping size) integer digits.
     * (Subject to isGroupingUsed().)
     *
     * For example, if this value is 2, and the grouping size is 3, then
     * 9999 -> "9999" and 10000 -> "10,000"
     *
     * The default value for this attribute is 0.
     * A value of 1, 0, or lower, means that the use of grouping separators
     * only depends on the grouping size (and on isGroupingUsed()).
     *
     * NOTE: The CLDR data is used in NumberFormatter but not in DecimalFormat.
     * This is for backwards compatibility reasons.
     *
     * For more control over grouping strategies, use NumberFormatter.
     *
     * @see setMinimumGroupingDigits
     * @see getGroupingSize
     * @stable ICU 64
     */
    int32_t getMinimumGroupingDigits() const;

    /**
     * Sets the minimum grouping digits. Setting the value to
     *  - 1: Turns off minimum grouping digits.
     *  - 0 or -1: The behavior is undefined.
     *  - UNUM_MINIMUM_GROUPING_DIGITS_AUTO: Display grouping using the default
     *      strategy for all locales.
     *  - UNUM_MINIMUM_GROUPING_DIGITS_MIN2: Display grouping using locale
     *      defaults, except do not show grouping on values smaller than 10000
     *      (such that there is a minimum of two digits before the first
     *      separator).
     *
     * For more control over grouping strategies, use NumberFormatter.
     *
     * @param newValue the new value of minimum grouping digits.
     * @see getMinimumGroupingDigits
     * @stable ICU 64
     */
    void setMinimumGroupingDigits(int32_t newValue);

    /**
     * Allows you to get the behavior of the decimal separator with integers.
     * (The decimal separator will always appear with decimals.)
     *
     * @return    true if the decimal separator always appear with decimals.
     * Example: Decimal ON: 12345 -> 12345.; OFF: 12345 -> 12345
     * @stable ICU 2.0
     */
    UBool isDecimalSeparatorAlwaysShown() const;

    /**
     * Allows you to set the behavior of the decimal separator with integers.
     * (The decimal separator will always appear with decimals.)
     *
     * @param newValue    set true if the decimal separator will always appear with decimals.
     * Example: Decimal ON: 12345 -> 12345.; OFF: 12345 -> 12345
     * @stable ICU 2.0
     */
    virtual void setDecimalSeparatorAlwaysShown(UBool newValue);

    /**
     * Allows you to get the parse behavior of the pattern decimal mark.
     *
     * @return    true if input must contain a match to decimal mark in pattern
     * @stable ICU 54
     */
    UBool isDecimalPatternMatchRequired() const;

    /**
     * Allows you to set the parse behavior of the pattern decimal mark.
     *
     * if true, the input must have a decimal mark if one was specified in the pattern. When
     * false the decimal mark may be omitted from the input.
     *
     * @param newValue    set true if input must contain a match to decimal mark in pattern
     * @stable ICU 54
     */
    virtual void setDecimalPatternMatchRequired(UBool newValue);

    /**
     * Returns whether to ignore exponents when parsing.
     *
     * @return Whether to ignore exponents when parsing.
     * @see #setParseNoExponent
     * @stable ICU 64
     */
    UBool isParseNoExponent() const;

    /**
     * Specifies whether to stop parsing when an exponent separator is encountered. For
     * example, parses "123E4" to 123 (with parse position 3) instead of 1230000 (with parse position
     * 5).
     *
     * @param value true to prevent exponents from being parsed; false to allow them to be parsed.
     * @stable ICU 64
     */
    void setParseNoExponent(UBool value);

    /**
     * Returns whether parsing is sensitive to case (lowercase/uppercase).
     *
     * @return Whether parsing is case-sensitive.
     * @see #setParseCaseSensitive
     * @stable ICU 64
     */
    UBool isParseCaseSensitive() const;

    /**
     * Whether to pay attention to case when parsing; default is to ignore case (perform
     * case-folding). For example, "A" == "a" in case-insensitive but not case-sensitive mode.
     *
     * Currency symbols are never case-folded. For example, "us$1.00" will not parse in case-insensitive
     * mode, even though "US$1.00" parses.
     *
     * @param value true to enable case-sensitive parsing (the default); false to force
     *              case-sensitive parsing behavior.
     * @stable ICU 64
     */
    void setParseCaseSensitive(UBool value);

    /**
     * Returns whether truncation of high-order integer digits should result in an error.
     * By default, setMaximumIntegerDigits truncates high-order digits silently.
     *
     * @return Whether an error code is set if high-order digits are truncated.
     * @see setFormatFailIfMoreThanMaxDigits
     * @stable ICU 64
     */
    UBool isFormatFailIfMoreThanMaxDigits() const;

    /**
     * Sets whether truncation of high-order integer digits should result in an error.
     * By default, setMaximumIntegerDigits truncates high-order digits silently.
     *
     * @param value Whether to set an error code if high-order digits are truncated.
     * @stable ICU 64
     */
    void setFormatFailIfMoreThanMaxDigits(UBool value);

    /**
     * Synthesizes a pattern string that represents the current state
     * of this Format object.
     *
     * @param result    Output param which will receive the pattern.
     *                  Previous contents are deleted.
     * @return          A reference to 'result'.
     * @see applyPattern
     * @stable ICU 2.0
     */
    virtual UnicodeString& toPattern(UnicodeString& result) const;

    /**
     * Synthesizes a localized pattern string that represents the current
     * state of this Format object.
     *
     * @param result    Output param which will receive the localized pattern.
     *                  Previous contents are deleted.
     * @return          A reference to 'result'.
     * @see applyPattern
     * @stable ICU 2.0
     */
    virtual UnicodeString& toLocalizedPattern(UnicodeString& result) const;

    /**
     * Apply the given pattern to this Format object.  A pattern is a
     * short-hand specification for the various formatting properties.
     * These properties can also be changed individually through the
     * various setter methods.
     * <P>
     * There is no limit to integer digits are set
     * by this routine, since that is the typical end-user desire;
     * use setMaximumInteger if you want to set a real value.
     * For negative numbers, use a second pattern, separated by a semicolon
     * <pre>
     * .      Example "#,#00.0#" -> 1,234.56
     * </pre>
     * This means a minimum of 2 integer digits, 1 fraction digit, and
     * a maximum of 2 fraction digits.
     * <pre>
     * .      Example: "#,#00.0#;(#,#00.0#)" for negatives in parentheses.
     * </pre>
     * In negative patterns, the minimum and maximum counts are ignored;
     * these are presumed to be set in the positive pattern.
     *
     * @param pattern    The pattern to be applied.
     * @param parseError Struct to receive information on position
     *                   of error if an error is encountered
     * @param status     Output param set to success/failure code on
     *                   exit. If the pattern is invalid, this will be
     *                   set to a failure result.
     * @stable ICU 2.0
     */
    virtual void applyPattern(const UnicodeString& pattern, UParseError& parseError, UErrorCode& status);

    /**
     * Sets the pattern.
     * @param pattern   The pattern to be applied.
     * @param status    Output param set to success/failure code on
     *                  exit. If the pattern is invalid, this will be
     *                  set to a failure result.
     * @stable ICU 2.0
     */
    virtual void applyPattern(const UnicodeString& pattern, UErrorCode& status);

    /**
     * Apply the given pattern to this Format object.  The pattern
     * is assumed to be in a localized notation. A pattern is a
     * short-hand specification for the various formatting properties.
     * These properties can also be changed individually through the
     * various setter methods.
     * <P>
     * There is no limit to integer digits are set
     * by this routine, since that is the typical end-user desire;
     * use setMaximumInteger if you want to set a real value.
     * For negative numbers, use a second pattern, separated by a semicolon
     * <pre>
     * .      Example "#,#00.0#" -> 1,234.56
     * </pre>
     * This means a minimum of 2 integer digits, 1 fraction digit, and
     * a maximum of 2 fraction digits.
     *
     * Example: "#,#00.0#;(#,#00.0#)" for negatives in parentheses.
     *
     * In negative patterns, the minimum and maximum counts are ignored;
     * these are presumed to be set in the positive pattern.
     *
     * @param pattern   The localized pattern to be applied.
     * @param parseError Struct to receive information on position
     *                   of error if an error is encountered
     * @param status    Output param set to success/failure code on
     *                  exit. If the pattern is invalid, this will be
     *                  set to a failure result.
     * @stable ICU 2.0
     */
    virtual void applyLocalizedPattern(const UnicodeString& pattern, UParseError& parseError,
                                       UErrorCode& status);

    /**
     * Apply the given pattern to this Format object.
     *
     * @param pattern   The localized pattern to be applied.
     * @param status    Output param set to success/failure code on
     *                  exit. If the pattern is invalid, this will be
     *                  set to a failure result.
     * @stable ICU 2.0
     */
    virtual void applyLocalizedPattern(const UnicodeString& pattern, UErrorCode& status);


    /**
     * Sets the maximum number of digits allowed in the integer portion of a
     * number. This override limits the integer digit count to 309.
     *
     * @param newValue    the new value of the maximum number of digits
     *                      allowed in the integer portion of a number.
     * @see NumberFormat#setMaximumIntegerDigits
     * @stable ICU 2.0
     */
    void setMaximumIntegerDigits(int32_t newValue) override;

    /**
     * Sets the minimum number of digits allowed in the integer portion of a
     * number. This override limits the integer digit count to 309.
     *
     * @param newValue    the new value of the minimum number of digits
     *                      allowed in the integer portion of a number.
     * @see NumberFormat#setMinimumIntegerDigits
     * @stable ICU 2.0
     */
    void setMinimumIntegerDigits(int32_t newValue) override;

    /**
     * Sets the maximum number of digits allowed in the fraction portion of a
     * number. This override limits the fraction digit count to 340.
     *
     * @param newValue    the new value of the maximum number of digits
     *                    allowed in the fraction portion of a number.
     * @see NumberFormat#setMaximumFractionDigits
     * @stable ICU 2.0
     */
    void setMaximumFractionDigits(int32_t newValue) override;

    /**
     * Sets the minimum number of digits allowed in the fraction portion of a
     * number. This override limits the fraction digit count to 340.
     *
     * @param newValue    the new value of the minimum number of digits
     *                    allowed in the fraction portion of a number.
     * @see NumberFormat#setMinimumFractionDigits
     * @stable ICU 2.0
     */
    void setMinimumFractionDigits(int32_t newValue) override;

    /**
     * Returns the minimum number of significant digits that will be
     * displayed. This value has no effect unless areSignificantDigitsUsed()
     * returns true.
     * @return the fewest significant digits that will be shown
     * @stable ICU 3.0
     */
    int32_t getMinimumSignificantDigits() const;

    /**
     * Returns the maximum number of significant digits that will be
     * displayed. This value has no effect unless areSignificantDigitsUsed()
     * returns true.
     * @return the most significant digits that will be shown
     * @stable ICU 3.0
     */
    int32_t getMaximumSignificantDigits() const;

    /**
     * Sets the minimum number of significant digits that will be
     * displayed.  If <code>min</code> is less than one then it is set
     * to one.  If the maximum significant digits count is less than
     * <code>min</code>, then it is set to <code>min</code>.
     * This function also enables the use of significant digits
     * by this formatter - areSignificantDigitsUsed() will return true.
     * @see #areSignificantDigitsUsed
     * @param min the fewest significant digits to be shown
     * @stable ICU 3.0
     */
    void setMinimumSignificantDigits(int32_t min);

    /**
     * Sets the maximum number of significant digits that will be
     * displayed.  If <code>max</code> is less than one then it is set
     * to one.  If the minimum significant digits count is greater
     * than <code>max</code>, then it is set to <code>max</code>.
     * This function also enables the use of significant digits
     * by this formatter - areSignificantDigitsUsed() will return true.
     * @see #areSignificantDigitsUsed
     * @param max the most significant digits to be shown
     * @stable ICU 3.0
     */
    void setMaximumSignificantDigits(int32_t max);

    /**
     * Returns true if significant digits are in use, or false if
     * integer and fraction digit counts are in use.
     * @return true if significant digits are in use
     * @stable ICU 3.0
     */
    UBool areSignificantDigitsUsed() const;

    /**
     * Sets whether significant digits are in use, or integer and
     * fraction digit counts are in use.
     * @param useSignificantDigits true to use significant digits, or
     * false to use integer and fraction digit counts
     * @stable ICU 3.0
     */
    void setSignificantDigitsUsed(UBool useSignificantDigits);

    /**
     * Sets the currency used to display currency
     * amounts.  This takes effect immediately, if this format is a
     * currency format.  If this format is not a currency format, then
     * the currency is used if and when this object becomes a
     * currency format through the application of a new pattern.
     * @param theCurrency a 3-letter ISO code indicating new currency
     * to use.  It need not be null-terminated.  May be the empty
     * string or nullptr to indicate no currency.
     * @param ec input-output error code
     * @stable ICU 3.0
     */
    void setCurrency(const char16_t* theCurrency, UErrorCode& ec) override;

#ifndef U_FORCE_HIDE_DEPRECATED_API
    /**
     * Sets the currency used to display currency amounts.  See
     * setCurrency(const char16_t*, UErrorCode&).
     * @deprecated ICU 3.0. Use setCurrency(const char16_t*, UErrorCode&).
     */
    virtual void setCurrency(const char16_t* theCurrency);
#endif  // U_FORCE_HIDE_DEPRECATED_API

    /**
     * Sets the `Currency Usage` object used to display currency.
     * This takes effect immediately, if this format is a
     * currency format.
     * @param newUsage new currency usage object to use.
     * @param ec input-output error code
     * @stable ICU 54
     */
    void setCurrencyUsage(UCurrencyUsage newUsage, UErrorCode* ec);

    /**
     * Returns the `Currency Usage` object used to display currency
     * @stable ICU 54
     */
    UCurrencyUsage getCurrencyUsage() const;

#ifndef U_HIDE_INTERNAL_API

    /**
     *  Format a number and save it into the given DecimalQuantity.
     *  Internal, not intended for public use.
     *  @internal
     */
    void formatToDecimalQuantity(double number, number::impl::DecimalQuantity& output,
                                 UErrorCode& status) const;

    /**
     *  Get a DecimalQuantity corresponding to a formattable as it would be
     *  formatted by this DecimalFormat.
     *  Internal, not intended for public use.
     *  @internal
     */
    void formatToDecimalQuantity(const Formattable& number, number::impl::DecimalQuantity& output,
                                 UErrorCode& status) const;

#endif  /* U_HIDE_INTERNAL_API */

    /**
     * Converts this DecimalFormat to a (Localized)NumberFormatter. Starting
     * in ICU 60, NumberFormatter is the recommended way to format numbers.
     * You can use the returned LocalizedNumberFormatter to format numbers and
     * get a FormattedNumber, which contains a string as well as additional
     * annotations about the formatted value.
     *
     * If a memory allocation failure occurs, the return value of this method
     * might be null. If you are concerned about correct recovery from
     * out-of-memory situations, use this pattern:
     *
     * <pre>
     * FormattedNumber result;
     * if (auto* ptr = df->toNumberFormatter(status)) {
     *     result = ptr->formatDouble(123, status);
     * }
     * </pre>
     *
     * If you are not concerned about out-of-memory situations, or if your
     * environment throws exceptions when memory allocation failure occurs,
     * you can chain the methods, like this:
     *
     * <pre>
     * FormattedNumber result = df
     *     ->toNumberFormatter(status)
     *     ->formatDouble(123, status);
     * </pre>
     *
     * NOTE: The returned LocalizedNumberFormatter is owned by this DecimalFormat.
     * If a non-const method is called on the DecimalFormat, or if the DecimalFormat
     * is deleted, the object becomes invalid. If you plan to keep the return value
     * beyond the lifetime of the DecimalFormat, copy it to a local variable:
     *
     * <pre>
     * LocalizedNumberFormatter lnf;
     * if (auto* ptr = df->toNumberFormatter(status)) {
     *     lnf = *ptr;
     * }
     * </pre>
     *
     * @param status Set on failure, like U_MEMORY_ALLOCATION_ERROR.
     * @return A pointer to an internal object, or nullptr on failure.
     *         Do not delete the return value!
     * @stable ICU 64
     */
    const number::LocalizedNumberFormatter* toNumberFormatter(UErrorCode& status) const;

    /**
     * Return the class ID for this class.  This is useful only for
     * comparing to a return value from getDynamicClassID().  For example:
     * <pre>
     * .      Base* polymorphic_pointer = createPolymorphicObject();
     * .      if (polymorphic_pointer->getDynamicClassID() ==
     * .          Derived::getStaticClassID()) ...
     * </pre>
     * @return          The class ID for all objects of this class.
     * @stable ICU 2.0
     */
    static UClassID U_EXPORT2 getStaticClassID();

    /**
     * Returns a unique class ID POLYMORPHICALLY.  Pure virtual override.
     * This method is to implement a simple version of RTTI, since not all
     * C++ compilers support genuine RTTI.  Polymorphic operator==() and
     * clone() methods call this method.
     *
     * @return          The class ID for this object. All objects of a
     *                  given class have the same class ID.  Objects of
     *                  other classes have different class IDs.
     * @stable ICU 2.0
     */
    UClassID getDynamicClassID() const override;

  private:

    /** Rebuilds the formatter object from the property bag. */
    void touch(UErrorCode& status);

    /** Rebuilds the formatter object, ignoring any error code. */
    void touchNoError();

    /**
     * Updates the property bag with settings from the given pattern.
     *
     * @param pattern The pattern string to parse.
     * @param ignoreRounding Whether to leave out rounding information (minFrac, maxFrac, and rounding
     *     increment) when parsing the pattern. This may be desirable if a custom rounding mode, such
     *     as CurrencyUsage, is to be used instead. One of {@link
     *     PatternStringParser#IGNORE_ROUNDING_ALWAYS}, {@link PatternStringParser#IGNORE_ROUNDING_IF_CURRENCY},
     *     or {@link PatternStringParser#IGNORE_ROUNDING_NEVER}.
     * @see PatternAndPropertyUtils#parseToExistingProperties
     */
    void setPropertiesFromPattern(const UnicodeString& pattern, int32_t ignoreRounding,
                                  UErrorCode& status);

    const numparse::impl::NumberParserImpl* getParser(UErrorCode& status) const;

    const numparse::impl::NumberParserImpl* getCurrencyParser(UErrorCode& status) const;

    static void fieldPositionHelper(
        const number::impl::UFormattedNumberData& formatted,
        FieldPosition& fieldPosition,
        int32_t offset,
        UErrorCode& status);

    static void fieldPositionIteratorHelper(
        const number::impl::UFormattedNumberData& formatted,
        FieldPositionIterator* fpi,
        int32_t offset,
        UErrorCode& status);

    void setupFastFormat();

    bool fastFormatDouble(double input, UnicodeString& output) const;

    bool fastFormatInt64(int64_t input, UnicodeString& output) const;

    void doFastFormatInt32(int32_t input, bool isNegative, UnicodeString& output) const;

    //=====================================================================================//
    //                                   INSTANCE FIELDS                                   //
    //=====================================================================================//


    // One instance field for the implementation, keep all fields inside of an implementation
    // class defined in number_mapper.h
    number::impl::DecimalFormatFields* fields = nullptr;

    // Allow child class CompactDecimalFormat to access fProperties:
    friend class CompactDecimalFormat;

    // Allow MeasureFormat to use fieldPositionHelper:
    friend class MeasureFormat;

};

U_NAMESPACE_END

#endif /* #if !UCONFIG_NO_FORMATTING */

#endif /* U_SHOW_CPLUSPLUS_API */

#endif // _DECIMFMT
//eof