| /* | |
| * Copyright (c) 2003, 2025, Oracle and/or its affiliates. All rights reserved. | |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | |
| * | |
| * This code is free software; you can redistribute it and/or modify it | |
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| * published by the Free Software Foundation. Oracle designates this | |
| * particular file as subject to the "Classpath" exception as provided | |
| * by Oracle in the LICENSE file that accompanied this code. | |
| * | |
| * This code is distributed in the hope that it will be useful, but WITHOUT | |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
| * version 2 for more details (a copy is included in the LICENSE file that | |
| * accompanied this code). | |
| * | |
| * You should have received a copy of the GNU General Public License version | |
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| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | |
| * | |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | |
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| * questions. | |
| */ | |
| /* | |
| * Portions Copyright IBM Corporation, 2001. All Rights Reserved. | |
| */ | |
| package java.math; | |
| /** | |
| * Specifies a <i>rounding policy</i> for numerical operations capable | |
| * of discarding precision. Each rounding mode indicates how the least | |
| * significant returned digit of a rounded result is to be calculated. | |
| * If fewer digits are returned than the digits needed to represent | |
| * the exact numerical result, the discarded digits will be referred | |
| * to as the <i>discarded fraction</i> regardless the digits' | |
| * contribution to the value of the number. In other words, | |
| * considered as a numerical value, the discarded fraction could have | |
| * an absolute value greater than one. | |
| * | |
| * <p>More generally, a rounding policy defines a mapping from the | |
| * real numbers to a subset of representable values. In the case of | |
| * {@link BigDecimal}, the representable values are a function of the | |
| * {@linkplain MathContext#getPrecision() precision} being used in the | |
| * computation. Assuming the mathematical result is within the | |
| * exponent range of {@code BigDecimal}, the mathematical result will | |
| * be exactly representable in the result precision or will fall | |
| * between two adjacent representable values. In the case of falling | |
| * between two representable values, the rounding policy determines | |
| * which of those two bracketing values is the result. For in-range | |
| * real numbers, for a given set of representable values, a rounding | |
| * policy maps a continuous segment of the real number line to a | |
| * single representable value where the real number numerically equal | |
| * to a representable value is mapped to that value. | |
| * | |
| * <p>Each rounding mode description includes a table listing how | |
| * different two-digit decimal values would round to a one digit | |
| * decimal value under the rounding mode in question. The result | |
| * column in the tables could be gotten by creating a | |
| * {@code BigDecimal} number with the specified value, forming a | |
| * {@link MathContext} object with the proper settings | |
| * ({@code precision} set to {@code 1}, and the | |
| * {@code roundingMode} set to the rounding mode in question), and | |
| * calling {@link BigDecimal#round round} on this number with the | |
| * proper {@code MathContext}. A summary table showing the results | |
| * of these rounding operations for all rounding modes appears below. | |
| * | |
| *<table class="striped"> | |
| * <caption><b>Summary of Rounding Operations Under Different Rounding Modes</b></caption> | |
| * <thead> | |
| * <tr><th scope="col" rowspan="2">Input Number</th><th scope="col"colspan=8>Result of rounding input to one digit with the given | |
| * rounding mode</th> | |
| * <tr style="vertical-align:top"> | |
| * <th>{@code UP}</th> | |
| * <th>{@code DOWN}</th> | |
| * <th>{@code CEILING}</th> | |
| * <th>{@code FLOOR}</th> | |
| * <th>{@code HALF_UP}</th> | |
| * <th>{@code HALF_DOWN}</th> | |
| * <th>{@code HALF_EVEN}</th> | |
| * <th>{@code UNNECESSARY}</th> | |
| * </thead> | |
| * <tbody style="text-align:right"> | |
| * | |
| * <tr><th scope="row">5.5</th> <td>6</td> <td>5</td> <td>6</td> <td>5</td> <td>6</td> <td>5</td> <td>6</td> <td>throw {@code ArithmeticException}</td> | |
| * <tr><th scope="row">2.5</th> <td>3</td> <td>2</td> <td>3</td> <td>2</td> <td>3</td> <td>2</td> <td>2</td> <td>throw {@code ArithmeticException}</td> | |
| * <tr><th scope="row">1.6</th> <td>2</td> <td>1</td> <td>2</td> <td>1</td> <td>2</td> <td>2</td> <td>2</td> <td>throw {@code ArithmeticException}</td> | |
| * <tr><th scope="row">1.1</th> <td>2</td> <td>1</td> <td>2</td> <td>1</td> <td>1</td> <td>1</td> <td>1</td> <td>throw {@code ArithmeticException}</td> | |
| * <tr><th scope="row">1.0</th> <td>1</td> <td>1</td> <td>1</td> <td>1</td> <td>1</td> <td>1</td> <td>1</td> <td>1</td> | |
| * <tr><th scope="row">-1.0</th> <td>-1</td> <td>-1</td> <td>-1</td> <td>-1</td> <td>-1</td> <td>-1</td> <td>-1</td> <td>-1</td> | |
| * <tr><th scope="row">-1.1</th> <td>-2</td> <td>-1</td> <td>-1</td> <td>-2</td> <td>-1</td> <td>-1</td> <td>-1</td> <td>throw {@code ArithmeticException}</td> | |
| * <tr><th scope="row">-1.6</th> <td>-2</td> <td>-1</td> <td>-1</td> <td>-2</td> <td>-2</td> <td>-2</td> <td>-2</td> <td>throw {@code ArithmeticException}</td> | |
| * <tr><th scope="row">-2.5</th> <td>-3</td> <td>-2</td> <td>-2</td> <td>-3</td> <td>-3</td> <td>-2</td> <td>-2</td> <td>throw {@code ArithmeticException}</td> | |
| * <tr><th scope="row">-5.5</th> <td>-6</td> <td>-5</td> <td>-5</td> <td>-6</td> <td>-6</td> <td>-5</td> <td>-6</td> <td>throw {@code ArithmeticException}</td> | |
| * </tbody> | |
| * </table> | |
| * | |
| * | |
| * <p>This {@code enum} is intended to replace the integer-based | |
| * enumeration of rounding mode constants in {@link BigDecimal} | |
| * ({@link BigDecimal#ROUND_UP}, {@link BigDecimal#ROUND_DOWN}, | |
| * etc. ). | |
| * | |
| * @apiNote | |
| * Five of the rounding modes declared in this class correspond to | |
| * rounding-direction attributes defined in the <cite>IEEE Standard | |
| * for Floating-Point Arithmetic</cite>. Where present, | |
| * this correspondence will be noted in the documentation of the | |
| * particular constant. | |
| * | |
| * @see BigDecimal | |
| * @see MathContext | |
| * @spec https://standards.ieee.org/ieee/754/6210/ | |
| * IEEE Standard for Floating-Point Arithmetic | |
| * @jls 15.4 Floating-point Expressions | |
| * | |
| * @author Josh Bloch | |
| * @author Mike Cowlishaw | |
| * @author Joseph D. Darcy | |
| * @since 1.5 | |
| */ | |
| @SuppressWarnings("deprecation") // Legacy rounding mode constants in BigDecimal | |
| public enum RoundingMode { | |
| /** | |
| * Rounding mode to round away from zero. Always increments the | |
| * digit prior to a non-zero discarded fraction. Note that this | |
| * rounding mode never decreases the magnitude of the calculated | |
| * value. | |
| * | |
| *<p>Example: | |
| *<table class="striped"> | |
| * <caption>Rounding mode UP Examples</caption> | |
| *<thead> | |
| *<tr style="vertical-align:top"><th scope="col">Input Number</th> | |
| * <th scope="col">Input rounded to one digit<br> with {@code UP} rounding | |
| *</thead> | |
| *<tbody style="text-align:right"> | |
| *<tr><th scope="row">5.5</th> <td>6</td> | |
| *<tr><th scope="row">2.5</th> <td>3</td> | |
| *<tr><th scope="row">1.6</th> <td>2</td> | |
| *<tr><th scope="row">1.1</th> <td>2</td> | |
| *<tr><th scope="row">1.0</th> <td>1</td> | |
| *<tr><th scope="row">-1.0</th> <td>-1</td> | |
| *<tr><th scope="row">-1.1</th> <td>-2</td> | |
| *<tr><th scope="row">-1.6</th> <td>-2</td> | |
| *<tr><th scope="row">-2.5</th> <td>-3</td> | |
| *<tr><th scope="row">-5.5</th> <td>-6</td> | |
| *</tbody> | |
| *</table> | |
| */ | |
| UP(BigDecimal.ROUND_UP), | |
| /** | |
| * Rounding mode to round towards zero. Never increments the digit | |
| * prior to a discarded fraction (i.e., truncates). Note that this | |
| * rounding mode never increases the magnitude of the calculated value. | |
| * | |
| * @apiNote | |
| * This rounding mode is analogous to the rounding policy used | |
| * for the {@code float} and {@code double} operators | |
| * remainder and conversion to an integer value (JLS {@jls | |
| * 15.4}). | |
| * This mode corresponds to the IEEE 754 rounding-direction | |
| * attribute roundTowardZero. | |
| * | |
| *<p>Example: | |
| *<table class="striped"> | |
| * <caption>Rounding mode DOWN Examples</caption> | |
| *<thead> | |
| *<tr style="vertical-align:top"><th scope="col">Input Number</th> | |
| * <th scope="col">Input rounded to one digit<br> with {@code DOWN} rounding | |
| *</thead> | |
| *<tbody style="text-align:right"> | |
| *<tr><th scope="row">5.5</th> <td>5</td> | |
| *<tr><th scope="row">2.5</th> <td>2</td> | |
| *<tr><th scope="row">1.6</th> <td>1</td> | |
| *<tr><th scope="row">1.1</th> <td>1</td> | |
| *<tr><th scope="row">1.0</th> <td>1</td> | |
| *<tr><th scope="row">-1.0</th> <td>-1</td> | |
| *<tr><th scope="row">-1.1</th> <td>-1</td> | |
| *<tr><th scope="row">-1.6</th> <td>-1</td> | |
| *<tr><th scope="row">-2.5</th> <td>-2</td> | |
| *<tr><th scope="row">-5.5</th> <td>-5</td> | |
| *</tbody> | |
| *</table> | |
| */ | |
| DOWN(BigDecimal.ROUND_DOWN), | |
| /** | |
| * Rounding mode to round towards positive infinity. If the | |
| * result is positive, behaves as for {@code RoundingMode.UP}; | |
| * if negative, behaves as for {@code RoundingMode.DOWN}. Note | |
| * that this rounding mode never decreases the calculated value. | |
| * This mode corresponds to the IEEE 754 rounding-direction | |
| * attribute roundTowardPositive. | |
| * | |
| *<p>Example: | |
| *<table class="striped"> | |
| * <caption>Rounding mode CEILING Examples</caption> | |
| *<thead> | |
| *<tr style="vertical-align:top"><th>Input Number</th> | |
| * <th>Input rounded to one digit<br> with {@code CEILING} rounding | |
| *</thead> | |
| *<tbody style="text-align:right"> | |
| *<tr><th scope="row">5.5</th> <td>6</td> | |
| *<tr><th scope="row">2.5</th> <td>3</td> | |
| *<tr><th scope="row">1.6</th> <td>2</td> | |
| *<tr><th scope="row">1.1</th> <td>2</td> | |
| *<tr><th scope="row">1.0</th> <td>1</td> | |
| *<tr><th scope="row">-1.0</th> <td>-1</td> | |
| *<tr><th scope="row">-1.1</th> <td>-1</td> | |
| *<tr><th scope="row">-1.6</th> <td>-1</td> | |
| *<tr><th scope="row">-2.5</th> <td>-2</td> | |
| *<tr><th scope="row">-5.5</th> <td>-5</td> | |
| *</tbody> | |
| *</table> | |
| */ | |
| CEILING(BigDecimal.ROUND_CEILING), | |
| /** | |
| * Rounding mode to round towards negative infinity. If the | |
| * result is positive, behave as for {@code RoundingMode.DOWN}; | |
| * if negative, behave as for {@code RoundingMode.UP}. Note that | |
| * this rounding mode never increases the calculated value. | |
| * This mode corresponds to the IEEE 754 rounding-direction | |
| * attribute roundTowardNegative. | |
| * | |
| *<p>Example: | |
| *<table class="striped"> | |
| * <caption>Rounding mode FLOOR Examples</caption> | |
| *<thead> | |
| *<tr style="vertical-align:top"><th scope="col">Input Number</th> | |
| * <th scope="col">Input rounded to one digit<br> with {@code FLOOR} rounding | |
| *</thead> | |
| *<tbody style="text-align:right"> | |
| *<tr><th scope="row">5.5</th> <td>5</td> | |
| *<tr><th scope="row">2.5</th> <td>2</td> | |
| *<tr><th scope="row">1.6</th> <td>1</td> | |
| *<tr><th scope="row">1.1</th> <td>1</td> | |
| *<tr><th scope="row">1.0</th> <td>1</td> | |
| *<tr><th scope="row">-1.0</th> <td>-1</td> | |
| *<tr><th scope="row">-1.1</th> <td>-2</td> | |
| *<tr><th scope="row">-1.6</th> <td>-2</td> | |
| *<tr><th scope="row">-2.5</th> <td>-3</td> | |
| *<tr><th scope="row">-5.5</th> <td>-6</td> | |
| *</tbody> | |
| *</table> | |
| */ | |
| FLOOR(BigDecimal.ROUND_FLOOR), | |
| /** | |
| * Rounding mode to round towards {@literal "nearest neighbor"} | |
| * unless both neighbors are equidistant, in which case round up. | |
| * Behaves as for {@code RoundingMode.UP} if the discarded | |
| * fraction is ≥ 0.5; otherwise, behaves as for | |
| * {@code RoundingMode.DOWN}. Note that this is the rounding | |
| * mode commonly taught at school. | |
| * This mode corresponds to the IEEE 754 rounding-direction | |
| * attribute roundTiesToAway. | |
| * | |
| *<p>Example: | |
| *<table class="striped"> | |
| * <caption>Rounding mode HALF_UP Examples</caption> | |
| *<thead> | |
| *<tr style="vertical-align:top"><th scope="col">Input Number</th> | |
| * <th scope="col">Input rounded to one digit<br> with {@code HALF_UP} rounding | |
| *</thead> | |
| *<tbody style="text-align:right"> | |
| *<tr><th scope="row">5.5</th> <td>6</td> | |
| *<tr><th scope="row">2.5</th> <td>3</td> | |
| *<tr><th scope="row">1.6</th> <td>2</td> | |
| *<tr><th scope="row">1.1</th> <td>1</td> | |
| *<tr><th scope="row">1.0</th> <td>1</td> | |
| *<tr><th scope="row">-1.0</th> <td>-1</td> | |
| *<tr><th scope="row">-1.1</th> <td>-1</td> | |
| *<tr><th scope="row">-1.6</th> <td>-2</td> | |
| *<tr><th scope="row">-2.5</th> <td>-3</td> | |
| *<tr><th scope="row">-5.5</th> <td>-6</td> | |
| *</tbody> | |
| *</table> | |
| */ | |
| HALF_UP(BigDecimal.ROUND_HALF_UP), | |
| /** | |
| * Rounding mode to round towards {@literal "nearest neighbor"} | |
| * unless both neighbors are equidistant, in which case round | |
| * down. Behaves as for {@code RoundingMode.UP} if the discarded | |
| * fraction is > 0.5; otherwise, behaves as for | |
| * {@code RoundingMode.DOWN}. | |
| * | |
| *<p>Example: | |
| *<table class="striped"> | |
| * <caption>Rounding mode HALF_DOWN Examples</caption> | |
| *<thead> | |
| *<tr style="vertical-align:top"><th scope="col">Input Number</th> | |
| * <th scope="col">Input rounded to one digit<br> with {@code HALF_DOWN} rounding | |
| *</thead> | |
| *<tbody style="text-align:right"> | |
| *<tr><th scope="row">5.5</th> <td>5</td> | |
| *<tr><th scope="row">2.5</th> <td>2</td> | |
| *<tr><th scope="row">1.6</th> <td>2</td> | |
| *<tr><th scope="row">1.1</th> <td>1</td> | |
| *<tr><th scope="row">1.0</th> <td>1</td> | |
| *<tr><th scope="row">-1.0</th> <td>-1</td> | |
| *<tr><th scope="row">-1.1</th> <td>-1</td> | |
| *<tr><th scope="row">-1.6</th> <td>-2</td> | |
| *<tr><th scope="row">-2.5</th> <td>-2</td> | |
| *<tr><th scope="row">-5.5</th> <td>-5</td> | |
| *</tbody> | |
| *</table> | |
| */ | |
| HALF_DOWN(BigDecimal.ROUND_HALF_DOWN), | |
| /** | |
| * Rounding mode to round towards the {@literal "nearest neighbor"} | |
| * unless both neighbors are equidistant, in which case, round | |
| * towards the even neighbor. Behaves as for | |
| * {@code RoundingMode.HALF_UP} if the digit to the left of the | |
| * discarded fraction is odd; behaves as for | |
| * {@code RoundingMode.HALF_DOWN} if it's even. | |
| * @apiNote | |
| * This | |
| * is the rounding mode that statistically minimizes cumulative | |
| * error when applied repeatedly over a sequence of calculations. | |
| * It is sometimes known as {@literal "Banker's rounding,"} and is | |
| * chiefly used in the USA. This rounding mode is analogous to | |
| * the rounding policy used for most {@code float} and {@code double} | |
| * arithmetic operators in Java (JLS {@jls 15.4}). | |
| * This mode corresponds to the IEEE 754 rounding-direction | |
| * attribute roundTiesToEven. | |
| * | |
| *<p>Example: | |
| *<table class="striped"> | |
| * <caption>Rounding mode HALF_EVEN Examples</caption> | |
| *<thead> | |
| *<tr style="vertical-align:top"><th scope="col">Input Number</th> | |
| * <th scope="col">Input rounded to one digit<br> with {@code HALF_EVEN} rounding | |
| *</thead> | |
| *<tbody style="text-align:right"> | |
| *<tr><th scope="row">5.5</th> <td>6</td> | |
| *<tr><th scope="row">2.5</th> <td>2</td> | |
| *<tr><th scope="row">1.6</th> <td>2</td> | |
| *<tr><th scope="row">1.1</th> <td>1</td> | |
| *<tr><th scope="row">1.0</th> <td>1</td> | |
| *<tr><th scope="row">-1.0</th> <td>-1</td> | |
| *<tr><th scope="row">-1.1</th> <td>-1</td> | |
| *<tr><th scope="row">-1.6</th> <td>-2</td> | |
| *<tr><th scope="row">-2.5</th> <td>-2</td> | |
| *<tr><th scope="row">-5.5</th> <td>-6</td> | |
| *</tbody> | |
| *</table> | |
| */ | |
| HALF_EVEN(BigDecimal.ROUND_HALF_EVEN), | |
| /** | |
| * Rounding mode to assert that the requested operation has an exact | |
| * result, hence no rounding is necessary. If this rounding mode is | |
| * specified on an operation that yields an inexact result, an | |
| * {@code ArithmeticException} is thrown. | |
| *<p>Example: | |
| *<table class="striped"> | |
| * <caption>Rounding mode UNNECESSARY Examples</caption> | |
| *<thead> | |
| *<tr style="vertical-align:top"><th scope="col">Input Number</th> | |
| * <th scope="col">Input rounded to one digit<br> with {@code UNNECESSARY} rounding | |
| *</thead> | |
| *<tbody style="text-align:right"> | |
| *<tr><th scope="row">5.5</th> <td>throw {@code ArithmeticException}</td> | |
| *<tr><th scope="row">2.5</th> <td>throw {@code ArithmeticException}</td> | |
| *<tr><th scope="row">1.6</th> <td>throw {@code ArithmeticException}</td> | |
| *<tr><th scope="row">1.1</th> <td>throw {@code ArithmeticException}</td> | |
| *<tr><th scope="row">1.0</th> <td>1</td> | |
| *<tr><th scope="row">-1.0</th> <td>-1</td> | |
| *<tr><th scope="row">-1.1</th> <td>throw {@code ArithmeticException}</td> | |
| *<tr><th scope="row">-1.6</th> <td>throw {@code ArithmeticException}</td> | |
| *<tr><th scope="row">-2.5</th> <td>throw {@code ArithmeticException}</td> | |
| *<tr><th scope="row">-5.5</th> <td>throw {@code ArithmeticException}</td> | |
| *</tbody> | |
| *</table> | |
| */ | |
| UNNECESSARY(BigDecimal.ROUND_UNNECESSARY); | |
| // Corresponding BigDecimal rounding constant | |
| final int oldMode; | |
| /** | |
| * Constructor | |
| * | |
| * @param oldMode The {@code BigDecimal} constant corresponding to | |
| * this mode | |
| */ | |
| private RoundingMode(int oldMode) { | |
| this.oldMode = oldMode; | |
| } | |
| /** | |
| * Returns the {@code RoundingMode} object corresponding to a | |
| * legacy integer rounding mode constant in {@link BigDecimal}. | |
| * | |
| * @param rm legacy integer rounding mode to convert | |
| * @return {@code RoundingMode} corresponding to the given integer. | |
| * @throws IllegalArgumentException integer is out of range | |
| */ | |
| public static RoundingMode valueOf(int rm) { | |
| return switch (rm) { | |
| case BigDecimal.ROUND_UP -> UP; | |
| case BigDecimal.ROUND_DOWN -> DOWN; | |
| case BigDecimal.ROUND_CEILING -> CEILING; | |
| case BigDecimal.ROUND_FLOOR -> FLOOR; | |
| case BigDecimal.ROUND_HALF_UP -> HALF_UP; | |
| case BigDecimal.ROUND_HALF_DOWN -> HALF_DOWN; | |
| case BigDecimal.ROUND_HALF_EVEN -> HALF_EVEN; | |
| case BigDecimal.ROUND_UNNECESSARY -> UNNECESSARY; | |
| default -> throw new IllegalArgumentException("argument out of range"); | |
| }; | |
| } | |
| } |