1 /* 2 * Copyright (c) 2003, 2017, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 /* 27 * Portions Copyright IBM Corporation, 2001. All Rights Reserved. 28 */ 29 package java.math; 30 31 /** 32 * Specifies a <i>rounding behavior</i> for numerical operations 33 * capable of discarding precision. Each rounding mode indicates how 34 * the least significant returned digit of a rounded result is to be 35 * calculated. If fewer digits are returned than the digits needed to 36 * represent the exact numerical result, the discarded digits will be 37 * referred to as the <i>discarded fraction</i> regardless the digits' 38 * contribution to the value of the number. In other words, 39 * considered as a numerical value, the discarded fraction could have 40 * an absolute value greater than one. 41 * 42 * <p>Each rounding mode description includes a table listing how 43 * different two-digit decimal values would round to a one digit 44 * decimal value under the rounding mode in question. The result 45 * column in the tables could be gotten by creating a 46 * {@code BigDecimal} number with the specified value, forming a 47 * {@link MathContext} object with the proper settings 48 * ({@code precision} set to {@code 1}, and the 49 * {@code roundingMode} set to the rounding mode in question), and 50 * calling {@link BigDecimal#round round} on this number with the 51 * proper {@code MathContext}. A summary table showing the results 52 * of these rounding operations for all rounding modes appears below. 53 * 54 *<table class="striped"> 55 * <caption><b>Summary of Rounding Operations Under Different Rounding Modes</b></caption> 56 * <thead> 57 * <tr><th scope="col" rowspan="2">Input Number</th><th scope="col"colspan=8>Result of rounding input to one digit with the given 58 * rounding mode</th> 59 * <tr style="vertical-align:top"> 60 * <th>{@code UP}</th> 61 * <th>{@code DOWN}</th> 62 * <th>{@code CEILING}</th> 63 * <th>{@code FLOOR}</th> 64 * <th>{@code HALF_UP}</th> 65 * <th>{@code HALF_DOWN}</th> 66 * <th>{@code HALF_EVEN}</th> 67 * <th>{@code UNNECESSARY}</th> 68 * </thead> 69 * <tbody style="text-align:right"> 70 * 71 * <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> 72 * <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> 73 * <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> 74 * <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> 75 * <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> 76 * <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> 77 * <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> 78 * <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> 79 * <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> 80 * <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> 81 * </tbody> 82 * </table> 83 * 84 * 85 * <p>This {@code enum} is intended to replace the integer-based 86 * enumeration of rounding mode constants in {@link BigDecimal} 87 * ({@link BigDecimal#ROUND_UP}, {@link BigDecimal#ROUND_DOWN}, 88 * etc. ). 89 * 90 * @see BigDecimal 91 * @see MathContext 92 * @author Josh Bloch 93 * @author Mike Cowlishaw 94 * @author Joseph D. Darcy 95 * @since 1.5 96 */ 97 @SuppressWarnings("deprecation") // Legacy rounding mode constants in BigDecimal 98 public enum RoundingMode { 99 100 /** 101 * Rounding mode to round away from zero. Always increments the 102 * digit prior to a non-zero discarded fraction. Note that this 103 * rounding mode never decreases the magnitude of the calculated 104 * value. 105 * 106 *<p>Example: 107 *<table class="striped"> 108 * <caption>Rounding mode UP Examples</caption> 109 *<thead> 110 *<tr style="vertical-align:top"><th scope="col">Input Number</th> 111 * <th scope="col">Input rounded to one digit<br> with {@code UP} rounding 112 *</thead> 113 *<tbody style="text-align:right"> 114 *<tr><th scope="row">5.5</th> <td>6</td> 115 *<tr><th scope="row">2.5</th> <td>3</td> 116 *<tr><th scope="row">1.6</th> <td>2</td> 117 *<tr><th scope="row">1.1</th> <td>2</td> 118 *<tr><th scope="row">1.0</th> <td>1</td> 119 *<tr><th scope="row">-1.0</th> <td>-1</td> 120 *<tr><th scope="row">-1.1</th> <td>-2</td> 121 *<tr><th scope="row">-1.6</th> <td>-2</td> 122 *<tr><th scope="row">-2.5</th> <td>-3</td> 123 *<tr><th scope="row">-5.5</th> <td>-6</td> 124 *</tbody> 125 *</table> 126 */ 127 UP(BigDecimal.ROUND_UP), 128 129 /** 130 * Rounding mode to round towards zero. Never increments the digit 131 * prior to a discarded fraction (i.e., truncates). Note that this 132 * rounding mode never increases the magnitude of the calculated value. 133 * 134 *<p>Example: 135 *<table class="striped"> 136 * <caption>Rounding mode DOWN Examples</caption> 137 *<thead> 138 *<tr style="vertical-align:top"><th scope="col">Input Number</th> 139 * <th scope="col">Input rounded to one digit<br> with {@code DOWN} rounding 140 *</thead> 141 *<tbody style="text-align:right"> 142 *<tr><th scope="row">5.5</th> <td>5</td> 143 *<tr><th scope="row">2.5</th> <td>2</td> 144 *<tr><th scope="row">1.6</th> <td>1</td> 145 *<tr><th scope="row">1.1</th> <td>1</td> 146 *<tr><th scope="row">1.0</th> <td>1</td> 147 *<tr><th scope="row">-1.0</th> <td>-1</td> 148 *<tr><th scope="row">-1.1</th> <td>-1</td> 149 *<tr><th scope="row">-1.6</th> <td>-1</td> 150 *<tr><th scope="row">-2.5</th> <td>-2</td> 151 *<tr><th scope="row">-5.5</th> <td>-5</td> 152 *</tbody> 153 *</table> 154 */ 155 DOWN(BigDecimal.ROUND_DOWN), 156 157 /** 158 * Rounding mode to round towards positive infinity. If the 159 * result is positive, behaves as for {@code RoundingMode.UP}; 160 * if negative, behaves as for {@code RoundingMode.DOWN}. Note 161 * that this rounding mode never decreases the calculated value. 162 * 163 *<p>Example: 164 *<table class="striped"> 165 * <caption>Rounding mode CEILING Examples</caption> 166 *<thead> 167 *<tr style="vertical-align:top"><th>Input Number</th> 168 * <th>Input rounded to one digit<br> with {@code CEILING} rounding 169 *</thead> 170 *<tbody style="text-align:right"> 171 *<tr><th scope="row">5.5</th> <td>6</td> 172 *<tr><th scope="row">2.5</th> <td>3</td> 173 *<tr><th scope="row">1.6</th> <td>2</td> 174 *<tr><th scope="row">1.1</th> <td>2</td> 175 *<tr><th scope="row">1.0</th> <td>1</td> 176 *<tr><th scope="row">-1.0</th> <td>-1</td> 177 *<tr><th scope="row">-1.1</th> <td>-1</td> 178 *<tr><th scope="row">-1.6</th> <td>-1</td> 179 *<tr><th scope="row">-2.5</th> <td>-2</td> 180 *<tr><th scope="row">-5.5</th> <td>-5</td> 181 *</tbody> 182 *</table> 183 */ 184 CEILING(BigDecimal.ROUND_CEILING), 185 186 /** 187 * Rounding mode to round towards negative infinity. If the 188 * result is positive, behave as for {@code RoundingMode.DOWN}; 189 * if negative, behave as for {@code RoundingMode.UP}. Note that 190 * this rounding mode never increases the calculated value. 191 * 192 *<p>Example: 193 *<table class="striped"> 194 * <caption>Rounding mode FLOOR Examples</caption> 195 *<thead> 196 *<tr style="vertical-align:top"><th scope="col">Input Number</th> 197 * <th scope="col">Input rounded to one digit<br> with {@code FLOOR} rounding 198 *</thead> 199 *<tbody style="text-align:right"> 200 *<tr><th scope="row">5.5</th> <td>5</td> 201 *<tr><th scope="row">2.5</th> <td>2</td> 202 *<tr><th scope="row">1.6</th> <td>1</td> 203 *<tr><th scope="row">1.1</th> <td>1</td> 204 *<tr><th scope="row">1.0</th> <td>1</td> 205 *<tr><th scope="row">-1.0</th> <td>-1</td> 206 *<tr><th scope="row">-1.1</th> <td>-2</td> 207 *<tr><th scope="row">-1.6</th> <td>-2</td> 208 *<tr><th scope="row">-2.5</th> <td>-3</td> 209 *<tr><th scope="row">-5.5</th> <td>-6</td> 210 *</tbody> 211 *</table> 212 */ 213 FLOOR(BigDecimal.ROUND_FLOOR), 214 215 /** 216 * Rounding mode to round towards {@literal "nearest neighbor"} 217 * unless both neighbors are equidistant, in which case round up. 218 * Behaves as for {@code RoundingMode.UP} if the discarded 219 * fraction is ≥ 0.5; otherwise, behaves as for 220 * {@code RoundingMode.DOWN}. Note that this is the rounding 221 * mode commonly taught at school. 222 * 223 *<p>Example: 224 *<table class="striped"> 225 * <caption>Rounding mode HALF_UP Examples</caption> 226 *<thead> 227 *<tr style="vertical-align:top"><th scope="col">Input Number</th> 228 * <th scope="col">Input rounded to one digit<br> with {@code HALF_UP} rounding 229 *</thead> 230 *<tbody style="text-align:right"> 231 *<tr><th scope="row">5.5</th> <td>6</td> 232 *<tr><th scope="row">2.5</th> <td>3</td> 233 *<tr><th scope="row">1.6</th> <td>2</td> 234 *<tr><th scope="row">1.1</th> <td>1</td> 235 *<tr><th scope="row">1.0</th> <td>1</td> 236 *<tr><th scope="row">-1.0</th> <td>-1</td> 237 *<tr><th scope="row">-1.1</th> <td>-1</td> 238 *<tr><th scope="row">-1.6</th> <td>-2</td> 239 *<tr><th scope="row">-2.5</th> <td>-3</td> 240 *<tr><th scope="row">-5.5</th> <td>-6</td> 241 *</tbody> 242 *</table> 243 */ 244 HALF_UP(BigDecimal.ROUND_HALF_UP), 245 246 /** 247 * Rounding mode to round towards {@literal "nearest neighbor"} 248 * unless both neighbors are equidistant, in which case round 249 * down. Behaves as for {@code RoundingMode.UP} if the discarded 250 * fraction is > 0.5; otherwise, behaves as for 251 * {@code RoundingMode.DOWN}. 252 * 253 *<p>Example: 254 *<table class="striped"> 255 * <caption>Rounding mode HALF_DOWN Examples</caption> 256 *<thead> 257 *<tr style="vertical-align:top"><th scope="col">Input Number</th> 258 * <th scope="col">Input rounded to one digit<br> with {@code HALF_DOWN} rounding 259 *</thead> 260 *<tbody style="text-align:right"> 261 *<tr><th scope="row">5.5</th> <td>5</td> 262 *<tr><th scope="row">2.5</th> <td>2</td> 263 *<tr><th scope="row">1.6</th> <td>2</td> 264 *<tr><th scope="row">1.1</th> <td>1</td> 265 *<tr><th scope="row">1.0</th> <td>1</td> 266 *<tr><th scope="row">-1.0</th> <td>-1</td> 267 *<tr><th scope="row">-1.1</th> <td>-1</td> 268 *<tr><th scope="row">-1.6</th> <td>-2</td> 269 *<tr><th scope="row">-2.5</th> <td>-2</td> 270 *<tr><th scope="row">-5.5</th> <td>-5</td> 271 *</tbody> 272 *</table> 273 */ 274 HALF_DOWN(BigDecimal.ROUND_HALF_DOWN), 275 276 /** 277 * Rounding mode to round towards the {@literal "nearest neighbor"} 278 * unless both neighbors are equidistant, in which case, round 279 * towards the even neighbor. Behaves as for 280 * {@code RoundingMode.HALF_UP} if the digit to the left of the 281 * discarded fraction is odd; behaves as for 282 * {@code RoundingMode.HALF_DOWN} if it's even. Note that this 283 * is the rounding mode that statistically minimizes cumulative 284 * error when applied repeatedly over a sequence of calculations. 285 * It is sometimes known as {@literal "Banker's rounding,"} and is 286 * chiefly used in the USA. This rounding mode is analogous to 287 * the rounding policy used for {@code float} and {@code double} 288 * arithmetic in Java. 289 * 290 *<p>Example: 291 *<table class="striped"> 292 * <caption>Rounding mode HALF_EVEN Examples</caption> 293 *<thead> 294 *<tr style="vertical-align:top"><th scope="col">Input Number</th> 295 * <th scope="col">Input rounded to one digit<br> with {@code HALF_EVEN} rounding 296 *</thead> 297 *<tbody style="text-align:right"> 298 *<tr><th scope="row">5.5</th> <td>6</td> 299 *<tr><th scope="row">2.5</th> <td>2</td> 300 *<tr><th scope="row">1.6</th> <td>2</td> 301 *<tr><th scope="row">1.1</th> <td>1</td> 302 *<tr><th scope="row">1.0</th> <td>1</td> 303 *<tr><th scope="row">-1.0</th> <td>-1</td> 304 *<tr><th scope="row">-1.1</th> <td>-1</td> 305 *<tr><th scope="row">-1.6</th> <td>-2</td> 306 *<tr><th scope="row">-2.5</th> <td>-2</td> 307 *<tr><th scope="row">-5.5</th> <td>-6</td> 308 *</tbody> 309 *</table> 310 */ 311 HALF_EVEN(BigDecimal.ROUND_HALF_EVEN), 312 313 /** 314 * Rounding mode to assert that the requested operation has an exact 315 * result, hence no rounding is necessary. If this rounding mode is 316 * specified on an operation that yields an inexact result, an 317 * {@code ArithmeticException} is thrown. 318 *<p>Example: 319 *<table class="striped"> 320 * <caption>Rounding mode UNNECESSARY Examples</caption> 321 *<thead> 322 *<tr style="vertical-align:top"><th scope="col">Input Number</th> 323 * <th scope="col">Input rounded to one digit<br> with {@code UNNECESSARY} rounding 324 *</thead> 325 *<tbody style="text-align:right"> 326 *<tr><th scope="row">5.5</th> <td>throw {@code ArithmeticException}</td> 327 *<tr><th scope="row">2.5</th> <td>throw {@code ArithmeticException}</td> 328 *<tr><th scope="row">1.6</th> <td>throw {@code ArithmeticException}</td> 329 *<tr><th scope="row">1.1</th> <td>throw {@code ArithmeticException}</td> 330 *<tr><th scope="row">1.0</th> <td>1</td> 331 *<tr><th scope="row">-1.0</th> <td>-1</td> 332 *<tr><th scope="row">-1.1</th> <td>throw {@code ArithmeticException}</td> 333 *<tr><th scope="row">-1.6</th> <td>throw {@code ArithmeticException}</td> 334 *<tr><th scope="row">-2.5</th> <td>throw {@code ArithmeticException}</td> 335 *<tr><th scope="row">-5.5</th> <td>throw {@code ArithmeticException}</td> 336 *</tbody> 337 *</table> 338 */ 339 UNNECESSARY(BigDecimal.ROUND_UNNECESSARY); 340 341 // Corresponding BigDecimal rounding constant 342 final int oldMode; 343 344 /** 345 * Constructor 346 * 347 * @param oldMode The {@code BigDecimal} constant corresponding to 348 * this mode 349 */ RoundingMode(int oldMode)350 private RoundingMode(int oldMode) { 351 this.oldMode = oldMode; 352 } 353 354 /** 355 * Returns the {@code RoundingMode} object corresponding to a 356 * legacy integer rounding mode constant in {@link BigDecimal}. 357 * 358 * @param rm legacy integer rounding mode to convert 359 * @return {@code RoundingMode} corresponding to the given integer. 360 * @throws IllegalArgumentException integer is out of range 361 */ valueOf(int rm)362 public static RoundingMode valueOf(int rm) { 363 switch(rm) { 364 365 case BigDecimal.ROUND_UP: 366 return UP; 367 368 case BigDecimal.ROUND_DOWN: 369 return DOWN; 370 371 case BigDecimal.ROUND_CEILING: 372 return CEILING; 373 374 case BigDecimal.ROUND_FLOOR: 375 return FLOOR; 376 377 case BigDecimal.ROUND_HALF_UP: 378 return HALF_UP; 379 380 case BigDecimal.ROUND_HALF_DOWN: 381 return HALF_DOWN; 382 383 case BigDecimal.ROUND_HALF_EVEN: 384 return HALF_EVEN; 385 386 case BigDecimal.ROUND_UNNECESSARY: 387 return UNNECESSARY; 388 389 default: 390 throw new IllegalArgumentException("argument out of range"); 391 } 392 } 393 } 394