J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 1994-2006 Sun Microsystems, Inc. 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. Sun designates this |
| 8 | * particular file as subject to the "Classpath" exception as provided |
| 9 | * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
| 22 | * CA 95054 USA or visit www.sun.com if you need additional information or |
| 23 | * have any questions. |
| 24 | */ |
| 25 | |
| 26 | package java.lang; |
| 27 | |
| 28 | import sun.misc.FloatingDecimal; |
| 29 | import sun.misc.FpUtils; |
| 30 | import sun.misc.FloatConsts; |
| 31 | import sun.misc.DoubleConsts; |
| 32 | |
| 33 | /** |
| 34 | * The {@code Float} class wraps a value of primitive type |
| 35 | * {@code float} in an object. An object of type |
| 36 | * {@code Float} contains a single field whose type is |
| 37 | * {@code float}. |
| 38 | * |
| 39 | * <p>In addition, this class provides several methods for converting a |
| 40 | * {@code float} to a {@code String} and a |
| 41 | * {@code String} to a {@code float}, as well as other |
| 42 | * constants and methods useful when dealing with a |
| 43 | * {@code float}. |
| 44 | * |
| 45 | * @author Lee Boynton |
| 46 | * @author Arthur van Hoff |
| 47 | * @author Joseph D. Darcy |
| 48 | * @since JDK1.0 |
| 49 | */ |
| 50 | public final class Float extends Number implements Comparable<Float> { |
| 51 | /** |
| 52 | * A constant holding the positive infinity of type |
| 53 | * {@code float}. It is equal to the value returned by |
| 54 | * {@code Float.intBitsToFloat(0x7f800000)}. |
| 55 | */ |
| 56 | public static final float POSITIVE_INFINITY = 1.0f / 0.0f; |
| 57 | |
| 58 | /** |
| 59 | * A constant holding the negative infinity of type |
| 60 | * {@code float}. It is equal to the value returned by |
| 61 | * {@code Float.intBitsToFloat(0xff800000)}. |
| 62 | */ |
| 63 | public static final float NEGATIVE_INFINITY = -1.0f / 0.0f; |
| 64 | |
| 65 | /** |
| 66 | * A constant holding a Not-a-Number (NaN) value of type |
| 67 | * {@code float}. It is equivalent to the value returned by |
| 68 | * {@code Float.intBitsToFloat(0x7fc00000)}. |
| 69 | */ |
| 70 | public static final float NaN = 0.0f / 0.0f; |
| 71 | |
| 72 | /** |
| 73 | * A constant holding the largest positive finite value of type |
| 74 | * {@code float}, (2-2<sup>-23</sup>)·2<sup>127</sup>. |
| 75 | * It is equal to the hexadecimal floating-point literal |
| 76 | * {@code 0x1.fffffeP+127f} and also equal to |
| 77 | * {@code Float.intBitsToFloat(0x7f7fffff)}. |
| 78 | */ |
| 79 | public static final float MAX_VALUE = 0x1.fffffeP+127f; // 3.4028235e+38f |
| 80 | |
| 81 | /** |
| 82 | * A constant holding the smallest positive normal value of type |
| 83 | * {@code float}, 2<sup>-126</sup>. It is equal to the |
| 84 | * hexadecimal floating-point literal {@code 0x1.0p-126f} and also |
| 85 | * equal to {@code Float.intBitsToFloat(0x00800000)}. |
| 86 | * |
| 87 | * @since 1.6 |
| 88 | */ |
| 89 | public static final float MIN_NORMAL = 0x1.0p-126f; // 1.17549435E-38f |
| 90 | |
| 91 | /** |
| 92 | * A constant holding the smallest positive nonzero value of type |
| 93 | * {@code float}, 2<sup>-149</sup>. It is equal to the |
| 94 | * hexadecimal floating-point literal {@code 0x0.000002P-126f} |
| 95 | * and also equal to {@code Float.intBitsToFloat(0x1)}. |
| 96 | */ |
| 97 | public static final float MIN_VALUE = 0x0.000002P-126f; // 1.4e-45f |
| 98 | |
| 99 | /** |
| 100 | * Maximum exponent a finite {@code float} variable may have. It |
| 101 | * is equal to the value returned by {@code |
| 102 | * Math.getExponent(Float.MAX_VALUE)}. |
| 103 | * |
| 104 | * @since 1.6 |
| 105 | */ |
| 106 | public static final int MAX_EXPONENT = 127; |
| 107 | |
| 108 | /** |
| 109 | * Minimum exponent a normalized {@code float} variable may have. |
| 110 | * It is equal to the value returned by {@code |
| 111 | * Math.getExponent(Float.MIN_NORMAL)}. |
| 112 | * |
| 113 | * @since 1.6 |
| 114 | */ |
| 115 | public static final int MIN_EXPONENT = -126; |
| 116 | |
| 117 | /** |
| 118 | * The number of bits used to represent a {@code float} value. |
| 119 | * |
| 120 | * @since 1.5 |
| 121 | */ |
| 122 | public static final int SIZE = 32; |
| 123 | |
| 124 | /** |
| 125 | * The {@code Class} instance representing the primitive type |
| 126 | * {@code float}. |
| 127 | * |
| 128 | * @since JDK1.1 |
| 129 | */ |
| 130 | public static final Class<Float> TYPE = Class.getPrimitiveClass("float"); |
| 131 | |
| 132 | /** |
| 133 | * Returns a string representation of the {@code float} |
| 134 | * argument. All characters mentioned below are ASCII characters. |
| 135 | * <ul> |
| 136 | * <li>If the argument is NaN, the result is the string |
| 137 | * "{@code NaN}". |
| 138 | * <li>Otherwise, the result is a string that represents the sign and |
| 139 | * magnitude (absolute value) of the argument. If the sign is |
| 140 | * negative, the first character of the result is |
| 141 | * '{@code -}' (<code>'\u002D'</code>); if the sign is |
| 142 | * positive, no sign character appears in the result. As for |
| 143 | * the magnitude <i>m</i>: |
| 144 | * <ul> |
| 145 | * <li>If <i>m</i> is infinity, it is represented by the characters |
| 146 | * {@code "Infinity"}; thus, positive infinity produces |
| 147 | * the result {@code "Infinity"} and negative infinity |
| 148 | * produces the result {@code "-Infinity"}. |
| 149 | * <li>If <i>m</i> is zero, it is represented by the characters |
| 150 | * {@code "0.0"}; thus, negative zero produces the result |
| 151 | * {@code "-0.0"} and positive zero produces the result |
| 152 | * {@code "0.0"}. |
| 153 | * <li> If <i>m</i> is greater than or equal to 10<sup>-3</sup> but |
| 154 | * less than 10<sup>7</sup>, then it is represented as the |
| 155 | * integer part of <i>m</i>, in decimal form with no leading |
| 156 | * zeroes, followed by '{@code .}' |
| 157 | * (<code>'\u002E'</code>), followed by one or more |
| 158 | * decimal digits representing the fractional part of |
| 159 | * <i>m</i>. |
| 160 | * <li> If <i>m</i> is less than 10<sup>-3</sup> or greater than or |
| 161 | * equal to 10<sup>7</sup>, then it is represented in |
| 162 | * so-called "computerized scientific notation." Let <i>n</i> |
| 163 | * be the unique integer such that 10<sup><i>n</i> </sup>≤ |
| 164 | * <i>m</i> {@literal <} 10<sup><i>n</i>+1</sup>; then let <i>a</i> |
| 165 | * be the mathematically exact quotient of <i>m</i> and |
| 166 | * 10<sup><i>n</i></sup> so that 1 ≤ <i>a</i> {@literal <} 10. |
| 167 | * The magnitude is then represented as the integer part of |
| 168 | * <i>a</i>, as a single decimal digit, followed by |
| 169 | * '{@code .}' (<code>'\u002E'</code>), followed by |
| 170 | * decimal digits representing the fractional part of |
| 171 | * <i>a</i>, followed by the letter '{@code E}' |
| 172 | * (<code>'\u0045'</code>), followed by a representation |
| 173 | * of <i>n</i> as a decimal integer, as produced by the |
| 174 | * method {@link java.lang.Integer#toString(int)}. |
| 175 | * |
| 176 | * </ul> |
| 177 | * </ul> |
| 178 | * How many digits must be printed for the fractional part of |
| 179 | * <i>m</i> or <i>a</i>? There must be at least one digit |
| 180 | * to represent the fractional part, and beyond that as many, but |
| 181 | * only as many, more digits as are needed to uniquely distinguish |
| 182 | * the argument value from adjacent values of type |
| 183 | * {@code float}. That is, suppose that <i>x</i> is the |
| 184 | * exact mathematical value represented by the decimal |
| 185 | * representation produced by this method for a finite nonzero |
| 186 | * argument <i>f</i>. Then <i>f</i> must be the {@code float} |
| 187 | * value nearest to <i>x</i>; or, if two {@code float} values are |
| 188 | * equally close to <i>x</i>, then <i>f</i> must be one of |
| 189 | * them and the least significant bit of the significand of |
| 190 | * <i>f</i> must be {@code 0}. |
| 191 | * |
| 192 | * <p>To create localized string representations of a floating-point |
| 193 | * value, use subclasses of {@link java.text.NumberFormat}. |
| 194 | * |
| 195 | * @param f the float to be converted. |
| 196 | * @return a string representation of the argument. |
| 197 | */ |
| 198 | public static String toString(float f) { |
| 199 | return new FloatingDecimal(f).toJavaFormatString(); |
| 200 | } |
| 201 | |
| 202 | /** |
| 203 | * Returns a hexadecimal string representation of the |
| 204 | * {@code float} argument. All characters mentioned below are |
| 205 | * ASCII characters. |
| 206 | * |
| 207 | * <ul> |
| 208 | * <li>If the argument is NaN, the result is the string |
| 209 | * "{@code NaN}". |
| 210 | * <li>Otherwise, the result is a string that represents the sign and |
| 211 | * magnitude (absolute value) of the argument. If the sign is negative, |
| 212 | * the first character of the result is '{@code -}' |
| 213 | * (<code>'\u002D'</code>); if the sign is positive, no sign character |
| 214 | * appears in the result. As for the magnitude <i>m</i>: |
| 215 | * |
| 216 | * <ul> |
| 217 | * <li>If <i>m</i> is infinity, it is represented by the string |
| 218 | * {@code "Infinity"}; thus, positive infinity produces the |
| 219 | * result {@code "Infinity"} and negative infinity produces |
| 220 | * the result {@code "-Infinity"}. |
| 221 | * |
| 222 | * <li>If <i>m</i> is zero, it is represented by the string |
| 223 | * {@code "0x0.0p0"}; thus, negative zero produces the result |
| 224 | * {@code "-0x0.0p0"} and positive zero produces the result |
| 225 | * {@code "0x0.0p0"}. |
| 226 | * |
| 227 | * <li>If <i>m</i> is a {@code float} value with a |
| 228 | * normalized representation, substrings are used to represent the |
| 229 | * significand and exponent fields. The significand is |
| 230 | * represented by the characters {@code "0x1."} |
| 231 | * followed by a lowercase hexadecimal representation of the rest |
| 232 | * of the significand as a fraction. Trailing zeros in the |
| 233 | * hexadecimal representation are removed unless all the digits |
| 234 | * are zero, in which case a single zero is used. Next, the |
| 235 | * exponent is represented by {@code "p"} followed |
| 236 | * by a decimal string of the unbiased exponent as if produced by |
| 237 | * a call to {@link Integer#toString(int) Integer.toString} on the |
| 238 | * exponent value. |
| 239 | * |
| 240 | * <li>If <i>m</i> is a {@code float} value with a subnormal |
| 241 | * representation, the significand is represented by the |
| 242 | * characters {@code "0x0."} followed by a |
| 243 | * hexadecimal representation of the rest of the significand as a |
| 244 | * fraction. Trailing zeros in the hexadecimal representation are |
| 245 | * removed. Next, the exponent is represented by |
| 246 | * {@code "p-126"}. Note that there must be at |
| 247 | * least one nonzero digit in a subnormal significand. |
| 248 | * |
| 249 | * </ul> |
| 250 | * |
| 251 | * </ul> |
| 252 | * |
| 253 | * <table border> |
| 254 | * <caption><h3>Examples</h3></caption> |
| 255 | * <tr><th>Floating-point Value</th><th>Hexadecimal String</th> |
| 256 | * <tr><td>{@code 1.0}</td> <td>{@code 0x1.0p0}</td> |
| 257 | * <tr><td>{@code -1.0}</td> <td>{@code -0x1.0p0}</td> |
| 258 | * <tr><td>{@code 2.0}</td> <td>{@code 0x1.0p1}</td> |
| 259 | * <tr><td>{@code 3.0}</td> <td>{@code 0x1.8p1}</td> |
| 260 | * <tr><td>{@code 0.5}</td> <td>{@code 0x1.0p-1}</td> |
| 261 | * <tr><td>{@code 0.25}</td> <td>{@code 0x1.0p-2}</td> |
| 262 | * <tr><td>{@code Float.MAX_VALUE}</td> |
| 263 | * <td>{@code 0x1.fffffep127}</td> |
| 264 | * <tr><td>{@code Minimum Normal Value}</td> |
| 265 | * <td>{@code 0x1.0p-126}</td> |
| 266 | * <tr><td>{@code Maximum Subnormal Value}</td> |
| 267 | * <td>{@code 0x0.fffffep-126}</td> |
| 268 | * <tr><td>{@code Float.MIN_VALUE}</td> |
| 269 | * <td>{@code 0x0.000002p-126}</td> |
| 270 | * </table> |
| 271 | * @param f the {@code float} to be converted. |
| 272 | * @return a hex string representation of the argument. |
| 273 | * @since 1.5 |
| 274 | * @author Joseph D. Darcy |
| 275 | */ |
| 276 | public static String toHexString(float f) { |
| 277 | if (Math.abs(f) < FloatConsts.MIN_NORMAL |
| 278 | && f != 0.0f ) {// float subnormal |
| 279 | // Adjust exponent to create subnormal double, then |
| 280 | // replace subnormal double exponent with subnormal float |
| 281 | // exponent |
| 282 | String s = Double.toHexString(FpUtils.scalb((double)f, |
| 283 | /* -1022+126 */ |
| 284 | DoubleConsts.MIN_EXPONENT- |
| 285 | FloatConsts.MIN_EXPONENT)); |
| 286 | return s.replaceFirst("p-1022$", "p-126"); |
| 287 | } |
| 288 | else // double string will be the same as float string |
| 289 | return Double.toHexString(f); |
| 290 | } |
| 291 | |
| 292 | /** |
| 293 | * Returns a {@code Float} object holding the |
| 294 | * {@code float} value represented by the argument string |
| 295 | * {@code s}. |
| 296 | * |
| 297 | * <p>If {@code s} is {@code null}, then a |
| 298 | * {@code NullPointerException} is thrown. |
| 299 | * |
| 300 | * <p>Leading and trailing whitespace characters in {@code s} |
| 301 | * are ignored. Whitespace is removed as if by the {@link |
| 302 | * String#trim} method; that is, both ASCII space and control |
| 303 | * characters are removed. The rest of {@code s} should |
| 304 | * constitute a <i>FloatValue</i> as described by the lexical |
| 305 | * syntax rules: |
| 306 | * |
| 307 | * <blockquote> |
| 308 | * <dl> |
| 309 | * <dt><i>FloatValue:</i> |
| 310 | * <dd><i>Sign<sub>opt</sub></i> {@code NaN} |
| 311 | * <dd><i>Sign<sub>opt</sub></i> {@code Infinity} |
| 312 | * <dd><i>Sign<sub>opt</sub> FloatingPointLiteral</i> |
| 313 | * <dd><i>Sign<sub>opt</sub> HexFloatingPointLiteral</i> |
| 314 | * <dd><i>SignedInteger</i> |
| 315 | * </dl> |
| 316 | * |
| 317 | * <p> |
| 318 | * |
| 319 | * <dl> |
| 320 | * <dt><i>HexFloatingPointLiteral</i>: |
| 321 | * <dd> <i>HexSignificand BinaryExponent FloatTypeSuffix<sub>opt</sub></i> |
| 322 | * </dl> |
| 323 | * |
| 324 | * <p> |
| 325 | * |
| 326 | * <dl> |
| 327 | * <dt><i>HexSignificand:</i> |
| 328 | * <dd><i>HexNumeral</i> |
| 329 | * <dd><i>HexNumeral</i> {@code .} |
| 330 | * <dd>{@code 0x} <i>HexDigits<sub>opt</sub> |
| 331 | * </i>{@code .}<i> HexDigits</i> |
| 332 | * <dd>{@code 0X}<i> HexDigits<sub>opt</sub> |
| 333 | * </i>{@code .} <i>HexDigits</i> |
| 334 | * </dl> |
| 335 | * |
| 336 | * <p> |
| 337 | * |
| 338 | * <dl> |
| 339 | * <dt><i>BinaryExponent:</i> |
| 340 | * <dd><i>BinaryExponentIndicator SignedInteger</i> |
| 341 | * </dl> |
| 342 | * |
| 343 | * <p> |
| 344 | * |
| 345 | * <dl> |
| 346 | * <dt><i>BinaryExponentIndicator:</i> |
| 347 | * <dd>{@code p} |
| 348 | * <dd>{@code P} |
| 349 | * </dl> |
| 350 | * |
| 351 | * </blockquote> |
| 352 | * |
| 353 | * where <i>Sign</i>, <i>FloatingPointLiteral</i>, |
| 354 | * <i>HexNumeral</i>, <i>HexDigits</i>, <i>SignedInteger</i> and |
| 355 | * <i>FloatTypeSuffix</i> are as defined in the lexical structure |
| 356 | * sections of the <a |
| 357 | * href="http://java.sun.com/docs/books/jls/html/">Java Language |
| 358 | * Specification</a>. If {@code s} does not have the form of |
| 359 | * a <i>FloatValue</i>, then a {@code NumberFormatException} |
| 360 | * is thrown. Otherwise, {@code s} is regarded as |
| 361 | * representing an exact decimal value in the usual |
| 362 | * "computerized scientific notation" or as an exact |
| 363 | * hexadecimal value; this exact numerical value is then |
| 364 | * conceptually converted to an "infinitely precise" |
| 365 | * binary value that is then rounded to type {@code float} |
| 366 | * by the usual round-to-nearest rule of IEEE 754 floating-point |
| 367 | * arithmetic, which includes preserving the sign of a zero |
| 368 | * value. Finally, a {@code Float} object representing this |
| 369 | * {@code float} value is returned. |
| 370 | * |
| 371 | * <p>To interpret localized string representations of a |
| 372 | * floating-point value, use subclasses of {@link |
| 373 | * java.text.NumberFormat}. |
| 374 | * |
| 375 | * <p>Note that trailing format specifiers, specifiers that |
| 376 | * determine the type of a floating-point literal |
| 377 | * ({@code 1.0f} is a {@code float} value; |
| 378 | * {@code 1.0d} is a {@code double} value), do |
| 379 | * <em>not</em> influence the results of this method. In other |
| 380 | * words, the numerical value of the input string is converted |
| 381 | * directly to the target floating-point type. In general, the |
| 382 | * two-step sequence of conversions, string to {@code double} |
| 383 | * followed by {@code double} to {@code float}, is |
| 384 | * <em>not</em> equivalent to converting a string directly to |
| 385 | * {@code float}. For example, if first converted to an |
| 386 | * intermediate {@code double} and then to |
| 387 | * {@code float}, the string<br> |
| 388 | * {@code "1.00000017881393421514957253748434595763683319091796875001d"}<br> |
| 389 | * results in the {@code float} value |
| 390 | * {@code 1.0000002f}; if the string is converted directly to |
| 391 | * {@code float}, <code>1.000000<b>1</b>f</code> results. |
| 392 | * |
| 393 | * <p>To avoid calling this method on an invalid string and having |
| 394 | * a {@code NumberFormatException} be thrown, the documentation |
| 395 | * for {@link Double#valueOf Double.valueOf} lists a regular |
| 396 | * expression which can be used to screen the input. |
| 397 | * |
| 398 | * @param s the string to be parsed. |
| 399 | * @return a {@code Float} object holding the value |
| 400 | * represented by the {@code String} argument. |
| 401 | * @throws NumberFormatException if the string does not contain a |
| 402 | * parsable number. |
| 403 | */ |
| 404 | public static Float valueOf(String s) throws NumberFormatException { |
| 405 | return new Float(FloatingDecimal.readJavaFormatString(s).floatValue()); |
| 406 | } |
| 407 | |
| 408 | /** |
| 409 | * Returns a {@code Float} instance representing the specified |
| 410 | * {@code float} value. |
| 411 | * If a new {@code Float} instance is not required, this method |
| 412 | * should generally be used in preference to the constructor |
| 413 | * {@link #Float(float)}, as this method is likely to yield |
| 414 | * significantly better space and time performance by caching |
| 415 | * frequently requested values. |
| 416 | * |
| 417 | * @param f a float value. |
| 418 | * @return a {@code Float} instance representing {@code f}. |
| 419 | * @since 1.5 |
| 420 | */ |
| 421 | public static Float valueOf(float f) { |
| 422 | return new Float(f); |
| 423 | } |
| 424 | |
| 425 | /** |
| 426 | * Returns a new {@code float} initialized to the value |
| 427 | * represented by the specified {@code String}, as performed |
| 428 | * by the {@code valueOf} method of class {@code Float}. |
| 429 | * |
| 430 | * @param s the string to be parsed. |
| 431 | * @return the {@code float} value represented by the string |
| 432 | * argument. |
| 433 | * @throws NumberFormatException if the string does not contain a |
| 434 | * parsable {@code float}. |
| 435 | * @see java.lang.Float#valueOf(String) |
| 436 | * @since 1.2 |
| 437 | */ |
| 438 | public static float parseFloat(String s) throws NumberFormatException { |
| 439 | return FloatingDecimal.readJavaFormatString(s).floatValue(); |
| 440 | } |
| 441 | |
| 442 | /** |
| 443 | * Returns {@code true} if the specified number is a |
| 444 | * Not-a-Number (NaN) value, {@code false} otherwise. |
| 445 | * |
| 446 | * @param v the value to be tested. |
| 447 | * @return {@code true} if the argument is NaN; |
| 448 | * {@code false} otherwise. |
| 449 | */ |
| 450 | static public boolean isNaN(float v) { |
| 451 | return (v != v); |
| 452 | } |
| 453 | |
| 454 | /** |
| 455 | * Returns {@code true} if the specified number is infinitely |
| 456 | * large in magnitude, {@code false} otherwise. |
| 457 | * |
| 458 | * @param v the value to be tested. |
| 459 | * @return {@code true} if the argument is positive infinity or |
| 460 | * negative infinity; {@code false} otherwise. |
| 461 | */ |
| 462 | static public boolean isInfinite(float v) { |
| 463 | return (v == POSITIVE_INFINITY) || (v == NEGATIVE_INFINITY); |
| 464 | } |
| 465 | |
| 466 | /** |
| 467 | * The value of the Float. |
| 468 | * |
| 469 | * @serial |
| 470 | */ |
| 471 | private final float value; |
| 472 | |
| 473 | /** |
| 474 | * Constructs a newly allocated {@code Float} object that |
| 475 | * represents the primitive {@code float} argument. |
| 476 | * |
| 477 | * @param value the value to be represented by the {@code Float}. |
| 478 | */ |
| 479 | public Float(float value) { |
| 480 | this.value = value; |
| 481 | } |
| 482 | |
| 483 | /** |
| 484 | * Constructs a newly allocated {@code Float} object that |
| 485 | * represents the argument converted to type {@code float}. |
| 486 | * |
| 487 | * @param value the value to be represented by the {@code Float}. |
| 488 | */ |
| 489 | public Float(double value) { |
| 490 | this.value = (float)value; |
| 491 | } |
| 492 | |
| 493 | /** |
| 494 | * Constructs a newly allocated {@code Float} object that |
| 495 | * represents the floating-point value of type {@code float} |
| 496 | * represented by the string. The string is converted to a |
| 497 | * {@code float} value as if by the {@code valueOf} method. |
| 498 | * |
| 499 | * @param s a string to be converted to a {@code Float}. |
| 500 | * @throws NumberFormatException if the string does not contain a |
| 501 | * parsable number. |
| 502 | * @see java.lang.Float#valueOf(java.lang.String) |
| 503 | */ |
| 504 | public Float(String s) throws NumberFormatException { |
| 505 | // REMIND: this is inefficient |
| 506 | this(valueOf(s).floatValue()); |
| 507 | } |
| 508 | |
| 509 | /** |
| 510 | * Returns {@code true} if this {@code Float} value is a |
| 511 | * Not-a-Number (NaN), {@code false} otherwise. |
| 512 | * |
| 513 | * @return {@code true} if the value represented by this object is |
| 514 | * NaN; {@code false} otherwise. |
| 515 | */ |
| 516 | public boolean isNaN() { |
| 517 | return isNaN(value); |
| 518 | } |
| 519 | |
| 520 | /** |
| 521 | * Returns {@code true} if this {@code Float} value is |
| 522 | * infinitely large in magnitude, {@code false} otherwise. |
| 523 | * |
| 524 | * @return {@code true} if the value represented by this object is |
| 525 | * positive infinity or negative infinity; |
| 526 | * {@code false} otherwise. |
| 527 | */ |
| 528 | public boolean isInfinite() { |
| 529 | return isInfinite(value); |
| 530 | } |
| 531 | |
| 532 | /** |
| 533 | * Returns a string representation of this {@code Float} object. |
| 534 | * The primitive {@code float} value represented by this object |
| 535 | * is converted to a {@code String} exactly as if by the method |
| 536 | * {@code toString} of one argument. |
| 537 | * |
| 538 | * @return a {@code String} representation of this object. |
| 539 | * @see java.lang.Float#toString(float) |
| 540 | */ |
| 541 | public String toString() { |
| 542 | return String.valueOf(value); |
| 543 | } |
| 544 | |
| 545 | /** |
| 546 | * Returns the value of this {@code Float} as a {@code byte} (by |
| 547 | * casting to a {@code byte}). |
| 548 | * |
| 549 | * @return the {@code float} value represented by this object |
| 550 | * converted to type {@code byte} |
| 551 | */ |
| 552 | public byte byteValue() { |
| 553 | return (byte)value; |
| 554 | } |
| 555 | |
| 556 | /** |
| 557 | * Returns the value of this {@code Float} as a {@code short} (by |
| 558 | * casting to a {@code short}). |
| 559 | * |
| 560 | * @return the {@code float} value represented by this object |
| 561 | * converted to type {@code short} |
| 562 | * @since JDK1.1 |
| 563 | */ |
| 564 | public short shortValue() { |
| 565 | return (short)value; |
| 566 | } |
| 567 | |
| 568 | /** |
| 569 | * Returns the value of this {@code Float} as an {@code int} (by |
| 570 | * casting to type {@code int}). |
| 571 | * |
| 572 | * @return the {@code float} value represented by this object |
| 573 | * converted to type {@code int} |
| 574 | */ |
| 575 | public int intValue() { |
| 576 | return (int)value; |
| 577 | } |
| 578 | |
| 579 | /** |
| 580 | * Returns value of this {@code Float} as a {@code long} (by |
| 581 | * casting to type {@code long}). |
| 582 | * |
| 583 | * @return the {@code float} value represented by this object |
| 584 | * converted to type {@code long} |
| 585 | */ |
| 586 | public long longValue() { |
| 587 | return (long)value; |
| 588 | } |
| 589 | |
| 590 | /** |
| 591 | * Returns the {@code float} value of this {@code Float} object. |
| 592 | * |
| 593 | * @return the {@code float} value represented by this object |
| 594 | */ |
| 595 | public float floatValue() { |
| 596 | return value; |
| 597 | } |
| 598 | |
| 599 | /** |
| 600 | * Returns the {@code double} value of this {@code Float} object. |
| 601 | * |
| 602 | * @return the {@code float} value represented by this |
| 603 | * object is converted to type {@code double} and the |
| 604 | * result of the conversion is returned. |
| 605 | */ |
| 606 | public double doubleValue() { |
| 607 | return (double)value; |
| 608 | } |
| 609 | |
| 610 | /** |
| 611 | * Returns a hash code for this {@code Float} object. The |
| 612 | * result is the integer bit representation, exactly as produced |
| 613 | * by the method {@link #floatToIntBits(float)}, of the primitive |
| 614 | * {@code float} value represented by this {@code Float} |
| 615 | * object. |
| 616 | * |
| 617 | * @return a hash code value for this object. |
| 618 | */ |
| 619 | public int hashCode() { |
| 620 | return floatToIntBits(value); |
| 621 | } |
| 622 | |
| 623 | /** |
| 624 | |
| 625 | * Compares this object against the specified object. The result |
| 626 | * is {@code true} if and only if the argument is not |
| 627 | * {@code null} and is a {@code Float} object that |
| 628 | * represents a {@code float} with the same value as the |
| 629 | * {@code float} represented by this object. For this |
| 630 | * purpose, two {@code float} values are considered to be the |
| 631 | * same if and only if the method {@link #floatToIntBits(float)} |
| 632 | * returns the identical {@code int} value when applied to |
| 633 | * each. |
| 634 | * |
| 635 | * <p>Note that in most cases, for two instances of class |
| 636 | * {@code Float}, {@code f1} and {@code f2}, the value |
| 637 | * of {@code f1.equals(f2)} is {@code true} if and only if |
| 638 | * |
| 639 | * <blockquote><pre> |
| 640 | * f1.floatValue() == f2.floatValue() |
| 641 | * </pre></blockquote> |
| 642 | * |
| 643 | * <p>also has the value {@code true}. However, there are two exceptions: |
| 644 | * <ul> |
| 645 | * <li>If {@code f1} and {@code f2} both represent |
| 646 | * {@code Float.NaN}, then the {@code equals} method returns |
| 647 | * {@code true}, even though {@code Float.NaN==Float.NaN} |
| 648 | * has the value {@code false}. |
| 649 | * <li>If {@code f1} represents {@code +0.0f} while |
| 650 | * {@code f2} represents {@code -0.0f}, or vice |
| 651 | * versa, the {@code equal} test has the value |
| 652 | * {@code false}, even though {@code 0.0f==-0.0f} |
| 653 | * has the value {@code true}. |
| 654 | * </ul> |
| 655 | * |
| 656 | * This definition allows hash tables to operate properly. |
| 657 | * |
| 658 | * @param obj the object to be compared |
| 659 | * @return {@code true} if the objects are the same; |
| 660 | * {@code false} otherwise. |
| 661 | * @see java.lang.Float#floatToIntBits(float) |
| 662 | */ |
| 663 | public boolean equals(Object obj) { |
| 664 | return (obj instanceof Float) |
| 665 | && (floatToIntBits(((Float)obj).value) == floatToIntBits(value)); |
| 666 | } |
| 667 | |
| 668 | /** |
| 669 | * Returns a representation of the specified floating-point value |
| 670 | * according to the IEEE 754 floating-point "single format" bit |
| 671 | * layout. |
| 672 | * |
| 673 | * <p>Bit 31 (the bit that is selected by the mask |
| 674 | * {@code 0x80000000}) represents the sign of the floating-point |
| 675 | * number. |
| 676 | * Bits 30-23 (the bits that are selected by the mask |
| 677 | * {@code 0x7f800000}) represent the exponent. |
| 678 | * Bits 22-0 (the bits that are selected by the mask |
| 679 | * {@code 0x007fffff}) represent the significand (sometimes called |
| 680 | * the mantissa) of the floating-point number. |
| 681 | * |
| 682 | * <p>If the argument is positive infinity, the result is |
| 683 | * {@code 0x7f800000}. |
| 684 | * |
| 685 | * <p>If the argument is negative infinity, the result is |
| 686 | * {@code 0xff800000}. |
| 687 | * |
| 688 | * <p>If the argument is NaN, the result is {@code 0x7fc00000}. |
| 689 | * |
| 690 | * <p>In all cases, the result is an integer that, when given to the |
| 691 | * {@link #intBitsToFloat(int)} method, will produce a floating-point |
| 692 | * value the same as the argument to {@code floatToIntBits} |
| 693 | * (except all NaN values are collapsed to a single |
| 694 | * "canonical" NaN value). |
| 695 | * |
| 696 | * @param value a floating-point number. |
| 697 | * @return the bits that represent the floating-point number. |
| 698 | */ |
| 699 | public static int floatToIntBits(float value) { |
| 700 | int result = floatToRawIntBits(value); |
| 701 | // Check for NaN based on values of bit fields, maximum |
| 702 | // exponent and nonzero significand. |
| 703 | if ( ((result & FloatConsts.EXP_BIT_MASK) == |
| 704 | FloatConsts.EXP_BIT_MASK) && |
| 705 | (result & FloatConsts.SIGNIF_BIT_MASK) != 0) |
| 706 | result = 0x7fc00000; |
| 707 | return result; |
| 708 | } |
| 709 | |
| 710 | /** |
| 711 | * Returns a representation of the specified floating-point value |
| 712 | * according to the IEEE 754 floating-point "single format" bit |
| 713 | * layout, preserving Not-a-Number (NaN) values. |
| 714 | * |
| 715 | * <p>Bit 31 (the bit that is selected by the mask |
| 716 | * {@code 0x80000000}) represents the sign of the floating-point |
| 717 | * number. |
| 718 | * Bits 30-23 (the bits that are selected by the mask |
| 719 | * {@code 0x7f800000}) represent the exponent. |
| 720 | * Bits 22-0 (the bits that are selected by the mask |
| 721 | * {@code 0x007fffff}) represent the significand (sometimes called |
| 722 | * the mantissa) of the floating-point number. |
| 723 | * |
| 724 | * <p>If the argument is positive infinity, the result is |
| 725 | * {@code 0x7f800000}. |
| 726 | * |
| 727 | * <p>If the argument is negative infinity, the result is |
| 728 | * {@code 0xff800000}. |
| 729 | * |
| 730 | * <p>If the argument is NaN, the result is the integer representing |
| 731 | * the actual NaN value. Unlike the {@code floatToIntBits} |
| 732 | * method, {@code floatToRawIntBits} does not collapse all the |
| 733 | * bit patterns encoding a NaN to a single "canonical" |
| 734 | * NaN value. |
| 735 | * |
| 736 | * <p>In all cases, the result is an integer that, when given to the |
| 737 | * {@link #intBitsToFloat(int)} method, will produce a |
| 738 | * floating-point value the same as the argument to |
| 739 | * {@code floatToRawIntBits}. |
| 740 | * |
| 741 | * @param value a floating-point number. |
| 742 | * @return the bits that represent the floating-point number. |
| 743 | * @since 1.3 |
| 744 | */ |
| 745 | public static native int floatToRawIntBits(float value); |
| 746 | |
| 747 | /** |
| 748 | * Returns the {@code float} value corresponding to a given |
| 749 | * bit representation. |
| 750 | * The argument is considered to be a representation of a |
| 751 | * floating-point value according to the IEEE 754 floating-point |
| 752 | * "single format" bit layout. |
| 753 | * |
| 754 | * <p>If the argument is {@code 0x7f800000}, the result is positive |
| 755 | * infinity. |
| 756 | * |
| 757 | * <p>If the argument is {@code 0xff800000}, the result is negative |
| 758 | * infinity. |
| 759 | * |
| 760 | * <p>If the argument is any value in the range |
| 761 | * {@code 0x7f800001} through {@code 0x7fffffff} or in |
| 762 | * the range {@code 0xff800001} through |
| 763 | * {@code 0xffffffff}, the result is a NaN. No IEEE 754 |
| 764 | * floating-point operation provided by Java can distinguish |
| 765 | * between two NaN values of the same type with different bit |
| 766 | * patterns. Distinct values of NaN are only distinguishable by |
| 767 | * use of the {@code Float.floatToRawIntBits} method. |
| 768 | * |
| 769 | * <p>In all other cases, let <i>s</i>, <i>e</i>, and <i>m</i> be three |
| 770 | * values that can be computed from the argument: |
| 771 | * |
| 772 | * <blockquote><pre> |
| 773 | * int s = ((bits >> 31) == 0) ? 1 : -1; |
| 774 | * int e = ((bits >> 23) & 0xff); |
| 775 | * int m = (e == 0) ? |
| 776 | * (bits & 0x7fffff) << 1 : |
| 777 | * (bits & 0x7fffff) | 0x800000; |
| 778 | * </pre></blockquote> |
| 779 | * |
| 780 | * Then the floating-point result equals the value of the mathematical |
| 781 | * expression <i>s</i>·<i>m</i>·2<sup><i>e</i>-150</sup>. |
| 782 | * |
| 783 | * <p>Note that this method may not be able to return a |
| 784 | * {@code float} NaN with exactly same bit pattern as the |
| 785 | * {@code int} argument. IEEE 754 distinguishes between two |
| 786 | * kinds of NaNs, quiet NaNs and <i>signaling NaNs</i>. The |
| 787 | * differences between the two kinds of NaN are generally not |
| 788 | * visible in Java. Arithmetic operations on signaling NaNs turn |
| 789 | * them into quiet NaNs with a different, but often similar, bit |
| 790 | * pattern. However, on some processors merely copying a |
| 791 | * signaling NaN also performs that conversion. In particular, |
| 792 | * copying a signaling NaN to return it to the calling method may |
| 793 | * perform this conversion. So {@code intBitsToFloat} may |
| 794 | * not be able to return a {@code float} with a signaling NaN |
| 795 | * bit pattern. Consequently, for some {@code int} values, |
| 796 | * {@code floatToRawIntBits(intBitsToFloat(start))} may |
| 797 | * <i>not</i> equal {@code start}. Moreover, which |
| 798 | * particular bit patterns represent signaling NaNs is platform |
| 799 | * dependent; although all NaN bit patterns, quiet or signaling, |
| 800 | * must be in the NaN range identified above. |
| 801 | * |
| 802 | * @param bits an integer. |
| 803 | * @return the {@code float} floating-point value with the same bit |
| 804 | * pattern. |
| 805 | */ |
| 806 | public static native float intBitsToFloat(int bits); |
| 807 | |
| 808 | /** |
| 809 | * Compares two {@code Float} objects numerically. There are |
| 810 | * two ways in which comparisons performed by this method differ |
| 811 | * from those performed by the Java language numerical comparison |
| 812 | * operators ({@code <, <=, ==, >=, >}) when |
| 813 | * applied to primitive {@code float} values: |
| 814 | * |
| 815 | * <ul><li> |
| 816 | * {@code Float.NaN} is considered by this method to |
| 817 | * be equal to itself and greater than all other |
| 818 | * {@code float} values |
| 819 | * (including {@code Float.POSITIVE_INFINITY}). |
| 820 | * <li> |
| 821 | * {@code 0.0f} is considered by this method to be greater |
| 822 | * than {@code -0.0f}. |
| 823 | * </ul> |
| 824 | * |
| 825 | * This ensures that the <i>natural ordering</i> of {@code Float} |
| 826 | * objects imposed by this method is <i>consistent with equals</i>. |
| 827 | * |
| 828 | * @param anotherFloat the {@code Float} to be compared. |
| 829 | * @return the value {@code 0} if {@code anotherFloat} is |
| 830 | * numerically equal to this {@code Float}; a value |
| 831 | * less than {@code 0} if this {@code Float} |
| 832 | * is numerically less than {@code anotherFloat}; |
| 833 | * and a value greater than {@code 0} if this |
| 834 | * {@code Float} is numerically greater than |
| 835 | * {@code anotherFloat}. |
| 836 | * |
| 837 | * @since 1.2 |
| 838 | * @see Comparable#compareTo(Object) |
| 839 | */ |
| 840 | public int compareTo(Float anotherFloat) { |
| 841 | return Float.compare(value, anotherFloat.value); |
| 842 | } |
| 843 | |
| 844 | /** |
| 845 | * Compares the two specified {@code float} values. The sign |
| 846 | * of the integer value returned is the same as that of the |
| 847 | * integer that would be returned by the call: |
| 848 | * <pre> |
| 849 | * new Float(f1).compareTo(new Float(f2)) |
| 850 | * </pre> |
| 851 | * |
| 852 | * @param f1 the first {@code float} to compare. |
| 853 | * @param f2 the second {@code float} to compare. |
| 854 | * @return the value {@code 0} if {@code f1} is |
| 855 | * numerically equal to {@code f2}; a value less than |
| 856 | * {@code 0} if {@code f1} is numerically less than |
| 857 | * {@code f2}; and a value greater than {@code 0} |
| 858 | * if {@code f1} is numerically greater than |
| 859 | * {@code f2}. |
| 860 | * @since 1.4 |
| 861 | */ |
| 862 | public static int compare(float f1, float f2) { |
| 863 | if (f1 < f2) |
| 864 | return -1; // Neither val is NaN, thisVal is smaller |
| 865 | if (f1 > f2) |
| 866 | return 1; // Neither val is NaN, thisVal is larger |
| 867 | |
| 868 | int thisBits = Float.floatToIntBits(f1); |
| 869 | int anotherBits = Float.floatToIntBits(f2); |
| 870 | |
| 871 | return (thisBits == anotherBits ? 0 : // Values are equal |
| 872 | (thisBits < anotherBits ? -1 : // (-0.0, 0.0) or (!NaN, NaN) |
| 873 | 1)); // (0.0, -0.0) or (NaN, !NaN) |
| 874 | } |
| 875 | |
| 876 | /** use serialVersionUID from JDK 1.0.2 for interoperability */ |
| 877 | private static final long serialVersionUID = -2671257302660747028L; |
| 878 | } |