1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341
/* * @(#)MathContext.java 1.5 06/04/07 * * Copyright 2006 Sun Microsystems, Inc. All rights reserved. * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */ /* * @(#)MathContext.java 1.x 01/xx/xx * * Copyright IBM Corporation, 1997, 2001. All Rights Reserved. * * This software is the proprietary information of Sun Microsystems, Inc. * and IBM Corporation. Use is subject to license terms. * */ package java.math; import java.io.*; /** * Immutable objects which encapsulate the context settings which * describe certain rules for numerical operators, such as those * implemented by the {@link BigDecimal} class. * * <p>The base-independent settings are: * <ol> * <li>{@code precision}: * the number of digits to be used for an operation; results are * rounded to this precision * * <li>{@code roundingMode}: * a {@link RoundingMode} object which specifies the algorithm to be * used for rounding. * </ol> * * @see BigDecimal * @see RoundingMode * @author Mike Cowlishaw * @author Joseph D. Darcy * @since 1.5 */ public final class MathContext implements Serializable { /* ----- Constants ----- */ // defaults for constructors private static final int DEFAULT_DIGITS = 9; private static final RoundingMode DEFAULT_ROUNDINGMODE = RoundingMode.HALF_UP; // Smallest values for digits (Maximum is Integer.MAX_VALUE) private static final int MIN_DIGITS = 0; // Serialization version private static final long serialVersionUID = 5579720004786848255L; /* ----- Public Properties ----- */ /** * A {@code MathContext} object whose settings have the values * required for unlimited precision arithmetic. * The values of the settings are: * <code> * precision=0 roundingMode=HALF_UP * </code> */ public static final MathContext UNLIMITED = new MathContext(0, RoundingMode.HALF_UP); /** * A {@code MathContext} object with a precision setting * matching the IEEE 754R Decimal32 format, 7 digits, and a * rounding mode of {@link RoundingMode#HALF_EVEN HALF_EVEN}, the * IEEE 754R default. */ public static final MathContext DECIMAL32 = new MathContext(7, RoundingMode.HALF_EVEN); /** * A {@code MathContext} object with a precision setting * matching the IEEE 754R Decimal64 format, 16 digits, and a * rounding mode of {@link RoundingMode#HALF_EVEN HALF_EVEN}, the * IEEE 754R default. */ public static final MathContext DECIMAL64 = new MathContext(16, RoundingMode.HALF_EVEN); /** * A {@code MathContext} object with a precision setting * matching the IEEE 754R Decimal128 format, 34 digits, and a * rounding mode of {@link RoundingMode#HALF_EVEN HALF_EVEN}, the * IEEE 754R default. */ public static final MathContext DECIMAL128 = new MathContext(34, RoundingMode.HALF_EVEN); /* ----- Shared Properties ----- */ /** * The number of digits to be used for an operation. A value of 0 * indicates that unlimited precision (as many digits as are * required) will be used. Note that leading zeros (in the * coefficient of a number) are never significant. * * <p>{@code precision} will always be non-negative. * * @serial */ final int precision; /** * The rounding algorithm to be used for an operation. * * @see RoundingMode * @serial */ final RoundingMode roundingMode; /** * Lookaside for the rounding points (the numbers which determine * whether the coefficient of a number will require rounding). * These will be present if {@code precision > 0} and * {@code precision <= MAX_LOOKASIDE}. In this case they will share the * {@code BigInteger int[]} array. Note that the transients * cannot be {@code final} because they are reconstructed on * deserialization. */ transient BigInteger roundingMax = null; transient BigInteger roundingMin = null; private static final int MAX_LOOKASIDE = 1000; /* ----- Constructors ----- */ /** * Constructs a new {@code MathContext} with the specified * precision and the {@link RoundingMode#HALF_UP HALF_UP} rounding * mode. * * @param setPrecision The non-negative {@code int} precision setting. * @throws IllegalArgumentException if the {@code setPrecision} parameter is less * than zero. */ public MathContext(int setPrecision) { this(setPrecision, DEFAULT_ROUNDINGMODE); return; } /** * Constructs a new {@code MathContext} with a specified * precision and rounding mode. * * @param setPrecision The non-negative {@code int} precision setting. * @param setRoundingMode The rounding mode to use. * @throws IllegalArgumentException if the {@code setPrecision} parameter is less * than zero. * @throws NullPointerException if the rounding mode argument is {@code null} */ public MathContext(int setPrecision, RoundingMode setRoundingMode) { if (setPrecision < MIN_DIGITS) throw new IllegalArgumentException("Digits < 0"); if (setRoundingMode == null) throw new NullPointerException("null RoundingMode"); precision = setPrecision; if (precision > 0 && precision <= MAX_LOOKASIDE) { roundingMax = BigInteger.TEN.pow(precision); roundingMin = roundingMax.negate(); } roundingMode = setRoundingMode; return; } /** * Constructs a new {@code MathContext} from a string. * * The string must be in the same format as that produced by the * {@link #toString} method. * * <p>An {@code IllegalArgumentException} is thrown if the precision * section of the string is out of range ({@code < 0}) or the string is * not in the format created by the {@link #toString} method. * * @param val The string to be parsed * @throws IllegalArgumentException if the precision section is out of range * or of incorrect format * @throws NullPointerException if the argument is {@code null} */ public MathContext(String val) { boolean bad = false; int setPrecision; if (val == null) throw new NullPointerException("null String"); try { // any error here is a string format problem if (!val.startsWith("precision=")) throw new RuntimeException(); int fence = val.indexOf(' '); // could be -1 int off = 10; // where value starts setPrecision = Integer.parseInt(val.substring(10, fence)); if (!val.startsWith("roundingMode=", fence+1)) throw new RuntimeException(); off = fence + 1 + 13; String str = val.substring(off, val.length()); roundingMode = RoundingMode.valueOf(str); } catch (RuntimeException re) { throw new IllegalArgumentException("bad string format"); } if (setPrecision < MIN_DIGITS) throw new IllegalArgumentException("Digits < 0"); // the other parameters cannot be invalid if we got here precision = setPrecision; if (precision > 0 && precision <= MAX_LOOKASIDE) { roundingMax = BigInteger.TEN.pow(precision); roundingMin = roundingMax.negate(); } } /** * Returns the {@code precision} setting. * This value is always non-negative. * * @return an {@code int} which is the value of the {@code precision} * setting */ public int getPrecision() { return precision; } /** * Returns the roundingMode setting. * This will be one of * {@link RoundingMode#CEILING}, * {@link RoundingMode#DOWN}, * {@link RoundingMode#FLOOR}, * {@link RoundingMode#HALF_DOWN}, * {@link RoundingMode#HALF_EVEN}, * {@link RoundingMode#HALF_UP}, * {@link RoundingMode#UNNECESSARY}, or * {@link RoundingMode#UP}. * * @return a {@code RoundingMode} object which is the value of the * {@code roundingMode} setting */ public RoundingMode getRoundingMode() { return roundingMode; } /** * Compares this {@code MathContext} with the specified * {@code Object} for equality. * * @param x {@code Object} to which this {@code MathContext} is to * be compared. * @return {@code true} if and only if the specified {@code Object} is * a {@code MathContext} object which has exactly the same * settings as this object */ public boolean equals(Object x){ MathContext mc; if (!(x instanceof MathContext)) return false; mc = (MathContext) x; return mc.precision == this.precision && mc.roundingMode == this.roundingMode; // no need for .equals() } /** * Returns the hash code for this {@code MathContext}. * * @return hash code for this {@code MathContext} */ public int hashCode() { return this.precision + roundingMode.hashCode() * 59; } /** * Returns the string representation of this {@code MathContext}. * The {@code String} returned represents the settings of the * {@code MathContext} object as two space-delimited words * (separated by a single space character, <tt>'\u0020'</tt>, * and with no leading or trailing white space), as follows: * <ol> * <li> * The string {@code "precision="}, immediately followed * by the value of the precision setting as a numeric string as if * generated by the {@link Integer#toString(int) Integer.toString} * method. * * <li> * The string {@code "roundingMode="}, immediately * followed by the value of the {@code roundingMode} setting as a * word. This word will be the same as the name of the * corresponding public constant in the {@link RoundingMode} * enum. * </ol> * <p> * For example: * <pre> * precision=9 roundingMode=HALF_UP * </pre> * * Additional words may be appended to the result of * {@code toString} in the future if more properties are added to * this class. * * @return a {@code String} representing the context settings */ public java.lang.String toString() { return "precision=" + precision + " " + "roundingMode=" + roundingMode.toString(); } // Private methods /** * Reconstitute the {@code MathContext} instance from a stream (that is, * deserialize it). * * @param s the stream being read. */ private synchronized void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException { s.defaultReadObject(); // read in all fields // validate possibly bad fields if (precision < MIN_DIGITS) { String message = "MathContext: invalid digits in stream"; throw new java.io.StreamCorruptedException(message); } if (roundingMode == null) { String message = "MathContext: null roundingMode in stream"; throw new java.io.StreamCorruptedException(message); } // Set the lookaside, if applicable if (precision <= MAX_LOOKASIDE) { roundingMax = BigInteger.TEN.pow(precision); roundingMin = roundingMax.negate(); } } }