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/* * Copyright (c) 2003, 2017, 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 * under the terms of the GNU General Public License version 2 only, as * 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 * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ /* * Portions Copyright IBM Corporation, 2001. All Rights Reserved. */ package java.math; /** * Specifies a <i>rounding behavior</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>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. ). * * @see BigDecimal * @see MathContext * @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. * *<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. * *<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. * *<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. * *<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. Note that 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 {@code float} and {@code double} * arithmetic in Java. * *<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) { switch (rm) { case BigDecimal.ROUND_UP: return UP; case BigDecimal.ROUND_DOWN: return DOWN; case BigDecimal.ROUND_CEILING: return CEILING; case BigDecimal.ROUND_FLOOR: return FLOOR; case BigDecimal.ROUND_HALF_UP: return HALF_UP; case BigDecimal.ROUND_HALF_DOWN: return HALF_DOWN; case BigDecimal.ROUND_HALF_EVEN: return HALF_EVEN; case BigDecimal.ROUND_UNNECESSARY: return UNNECESSARY; default: throw new IllegalArgumentException("argument out of range"); } } }