1/* 2 * Copyright (C) 2014 The Android Open Source Project 3 * Copyright (c) 1994, 2013, Oracle and/or its affiliates. All rights reserved. 4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 5 * 6 * This code is free software; you can redistribute it and/or modify it 7 * under the terms of the GNU General Public License version 2 only, as 8 * published by the Free Software Foundation. Oracle designates this 9 * particular file as subject to the "Classpath" exception as provided 10 * by Oracle in the LICENSE file that accompanied this code. 11 * 12 * This code is distributed in the hope that it will be useful, but WITHOUT 13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 15 * version 2 for more details (a copy is included in the LICENSE file that 16 * accompanied this code). 17 * 18 * You should have received a copy of the GNU General Public License version 19 * 2 along with this work; if not, write to the Free Software Foundation, 20 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 21 * 22 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 23 * or visit www.oracle.com if you need additional information or have any 24 * questions. 25 */ 26 27package java.lang; 28 29import sun.misc.FpUtils; 30import sun.misc.FloatConsts; 31import 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 */ 50public 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 number of bytes used to represent a {@code float} value. 126 * 127 * @since 1.8 128 */ 129 public static final int BYTES = SIZE / Byte.SIZE; 130 131 /** 132 * The {@code Class} instance representing the primitive type 133 * {@code float}. 134 * 135 * @since JDK1.1 136 */ 137 public static final Class<Float> TYPE = (Class<Float>) float[].class.getComponentType(); 138 139 /** 140 * Returns a string representation of the {@code float} 141 * argument. All characters mentioned below are ASCII characters. 142 * <ul> 143 * <li>If the argument is NaN, the result is the string 144 * "{@code NaN}". 145 * <li>Otherwise, the result is a string that represents the sign and 146 * magnitude (absolute value) of the argument. If the sign is 147 * negative, the first character of the result is 148 * '{@code -}' (<code>'\u002D'</code>); if the sign is 149 * positive, no sign character appears in the result. As for 150 * the magnitude <i>m</i>: 151 * <ul> 152 * <li>If <i>m</i> is infinity, it is represented by the characters 153 * {@code "Infinity"}; thus, positive infinity produces 154 * the result {@code "Infinity"} and negative infinity 155 * produces the result {@code "-Infinity"}. 156 * <li>If <i>m</i> is zero, it is represented by the characters 157 * {@code "0.0"}; thus, negative zero produces the result 158 * {@code "-0.0"} and positive zero produces the result 159 * {@code "0.0"}. 160 * <li> If <i>m</i> is greater than or equal to 10<sup>-3</sup> but 161 * less than 10<sup>7</sup>, then it is represented as the 162 * integer part of <i>m</i>, in decimal form with no leading 163 * zeroes, followed by '{@code .}' 164 * (<code>'\u002E'</code>), followed by one or more 165 * decimal digits representing the fractional part of 166 * <i>m</i>. 167 * <li> If <i>m</i> is less than 10<sup>-3</sup> or greater than or 168 * equal to 10<sup>7</sup>, then it is represented in 169 * so-called "computerized scientific notation." Let <i>n</i> 170 * be the unique integer such that 10<sup><i>n</i> </sup>≤ 171 * <i>m</i> {@literal <} 10<sup><i>n</i>+1</sup>; then let <i>a</i> 172 * be the mathematically exact quotient of <i>m</i> and 173 * 10<sup><i>n</i></sup> so that 1 ≤ <i>a</i> {@literal <} 10. 174 * The magnitude is then represented as the integer part of 175 * <i>a</i>, as a single decimal digit, followed by 176 * '{@code .}' (<code>'\u002E'</code>), followed by 177 * decimal digits representing the fractional part of 178 * <i>a</i>, followed by the letter '{@code E}' 179 * (<code>'\u0045'</code>), followed by a representation 180 * of <i>n</i> as a decimal integer, as produced by the 181 * method {@link java.lang.Integer#toString(int)}. 182 * 183 * </ul> 184 * </ul> 185 * How many digits must be printed for the fractional part of 186 * <i>m</i> or <i>a</i>? There must be at least one digit 187 * to represent the fractional part, and beyond that as many, but 188 * only as many, more digits as are needed to uniquely distinguish 189 * the argument value from adjacent values of type 190 * {@code float}. That is, suppose that <i>x</i> is the 191 * exact mathematical value represented by the decimal 192 * representation produced by this method for a finite nonzero 193 * argument <i>f</i>. Then <i>f</i> must be the {@code float} 194 * value nearest to <i>x</i>; or, if two {@code float} values are 195 * equally close to <i>x</i>, then <i>f</i> must be one of 196 * them and the least significant bit of the significand of 197 * <i>f</i> must be {@code 0}. 198 * 199 * <p>To create localized string representations of a floating-point 200 * value, use subclasses of {@link java.text.NumberFormat}. 201 * 202 * @param f the float to be converted. 203 * @return a string representation of the argument. 204 */ 205 public static String toString(float f) { 206 return FloatingDecimal.getThreadLocalInstance().loadFloat(f).toJavaFormatString(); 207 } 208 209 /** 210 * Returns a hexadecimal string representation of the 211 * {@code float} argument. All characters mentioned below are 212 * ASCII characters. 213 * 214 * <ul> 215 * <li>If the argument is NaN, the result is the string 216 * "{@code NaN}". 217 * <li>Otherwise, the result is a string that represents the sign and 218 * magnitude (absolute value) of the argument. If the sign is negative, 219 * the first character of the result is '{@code -}' 220 * (<code>'\u002D'</code>); if the sign is positive, no sign character 221 * appears in the result. As for the magnitude <i>m</i>: 222 * 223 * <ul> 224 * <li>If <i>m</i> is infinity, it is represented by the string 225 * {@code "Infinity"}; thus, positive infinity produces the 226 * result {@code "Infinity"} and negative infinity produces 227 * the result {@code "-Infinity"}. 228 * 229 * <li>If <i>m</i> is zero, it is represented by the string 230 * {@code "0x0.0p0"}; thus, negative zero produces the result 231 * {@code "-0x0.0p0"} and positive zero produces the result 232 * {@code "0x0.0p0"}. 233 * 234 * <li>If <i>m</i> is a {@code float} value with a 235 * normalized representation, substrings are used to represent the 236 * significand and exponent fields. The significand is 237 * represented by the characters {@code "0x1."} 238 * followed by a lowercase hexadecimal representation of the rest 239 * of the significand as a fraction. Trailing zeros in the 240 * hexadecimal representation are removed unless all the digits 241 * are zero, in which case a single zero is used. Next, the 242 * exponent is represented by {@code "p"} followed 243 * by a decimal string of the unbiased exponent as if produced by 244 * a call to {@link Integer#toString(int) Integer.toString} on the 245 * exponent value. 246 * 247 * <li>If <i>m</i> is a {@code float} value with a subnormal 248 * representation, the significand is represented by the 249 * characters {@code "0x0."} followed by a 250 * hexadecimal representation of the rest of the significand as a 251 * fraction. Trailing zeros in the hexadecimal representation are 252 * removed. Next, the exponent is represented by 253 * {@code "p-126"}. Note that there must be at 254 * least one nonzero digit in a subnormal significand. 255 * 256 * </ul> 257 * 258 * </ul> 259 * 260 * <table border> 261 * <caption><h3>Examples</h3></caption> 262 * <tr><th>Floating-point Value</th><th>Hexadecimal String</th> 263 * <tr><td>{@code 1.0}</td> <td>{@code 0x1.0p0}</td> 264 * <tr><td>{@code -1.0}</td> <td>{@code -0x1.0p0}</td> 265 * <tr><td>{@code 2.0}</td> <td>{@code 0x1.0p1}</td> 266 * <tr><td>{@code 3.0}</td> <td>{@code 0x1.8p1}</td> 267 * <tr><td>{@code 0.5}</td> <td>{@code 0x1.0p-1}</td> 268 * <tr><td>{@code 0.25}</td> <td>{@code 0x1.0p-2}</td> 269 * <tr><td>{@code Float.MAX_VALUE}</td> 270 * <td>{@code 0x1.fffffep127}</td> 271 * <tr><td>{@code Minimum Normal Value}</td> 272 * <td>{@code 0x1.0p-126}</td> 273 * <tr><td>{@code Maximum Subnormal Value}</td> 274 * <td>{@code 0x0.fffffep-126}</td> 275 * <tr><td>{@code Float.MIN_VALUE}</td> 276 * <td>{@code 0x0.000002p-126}</td> 277 * </table> 278 * @param f the {@code float} to be converted. 279 * @return a hex string representation of the argument. 280 * @since 1.5 281 * @author Joseph D. Darcy 282 */ 283 public static String toHexString(float f) { 284 if (Math.abs(f) < FloatConsts.MIN_NORMAL 285 && f != 0.0f ) {// float subnormal 286 // Adjust exponent to create subnormal double, then 287 // replace subnormal double exponent with subnormal float 288 // exponent 289 String s = Double.toHexString(FpUtils.scalb((double)f, 290 /* -1022+126 */ 291 DoubleConsts.MIN_EXPONENT- 292 FloatConsts.MIN_EXPONENT)); 293 return s.replaceFirst("p-1022$", "p-126"); 294 } 295 else // double string will be the same as float string 296 return Double.toHexString(f); 297 } 298 299 /** 300 * Returns a {@code Float} object holding the 301 * {@code float} value represented by the argument string 302 * {@code s}. 303 * 304 * <p>If {@code s} is {@code null}, then a 305 * {@code NullPointerException} is thrown. 306 * 307 * <p>Leading and trailing whitespace characters in {@code s} 308 * are ignored. Whitespace is removed as if by the {@link 309 * String#trim} method; that is, both ASCII space and control 310 * characters are removed. The rest of {@code s} should 311 * constitute a <i>FloatValue</i> as described by the lexical 312 * syntax rules: 313 * 314 * <blockquote> 315 * <dl> 316 * <dt><i>FloatValue:</i> 317 * <dd><i>Sign<sub>opt</sub></i> {@code NaN} 318 * <dd><i>Sign<sub>opt</sub></i> {@code Infinity} 319 * <dd><i>Sign<sub>opt</sub> FloatingPointLiteral</i> 320 * <dd><i>Sign<sub>opt</sub> HexFloatingPointLiteral</i> 321 * <dd><i>SignedInteger</i> 322 * </dl> 323 * 324 * <p> 325 * 326 * <dl> 327 * <dt><i>HexFloatingPointLiteral</i>: 328 * <dd> <i>HexSignificand BinaryExponent FloatTypeSuffix<sub>opt</sub></i> 329 * </dl> 330 * 331 * <p> 332 * 333 * <dl> 334 * <dt><i>HexSignificand:</i> 335 * <dd><i>HexNumeral</i> 336 * <dd><i>HexNumeral</i> {@code .} 337 * <dd>{@code 0x} <i>HexDigits<sub>opt</sub> 338 * </i>{@code .}<i> HexDigits</i> 339 * <dd>{@code 0X}<i> HexDigits<sub>opt</sub> 340 * </i>{@code .} <i>HexDigits</i> 341 * </dl> 342 * 343 * <p> 344 * 345 * <dl> 346 * <dt><i>BinaryExponent:</i> 347 * <dd><i>BinaryExponentIndicator SignedInteger</i> 348 * </dl> 349 * 350 * <p> 351 * 352 * <dl> 353 * <dt><i>BinaryExponentIndicator:</i> 354 * <dd>{@code p} 355 * <dd>{@code P} 356 * </dl> 357 * 358 * </blockquote> 359 * 360 * where <i>Sign</i>, <i>FloatingPointLiteral</i>, 361 * <i>HexNumeral</i>, <i>HexDigits</i>, <i>SignedInteger</i> and 362 * <i>FloatTypeSuffix</i> are as defined in the lexical structure 363 * sections of 364 * <cite>The Java™ Language Specification</cite>, 365 * except that underscores are not accepted between digits. 366 * If {@code s} does not have the form of 367 * a <i>FloatValue</i>, then a {@code NumberFormatException} 368 * is thrown. Otherwise, {@code s} is regarded as 369 * representing an exact decimal value in the usual 370 * "computerized scientific notation" or as an exact 371 * hexadecimal value; this exact numerical value is then 372 * conceptually converted to an "infinitely precise" 373 * binary value that is then rounded to type {@code float} 374 * by the usual round-to-nearest rule of IEEE 754 floating-point 375 * arithmetic, which includes preserving the sign of a zero 376 * value. 377 * 378 * Note that the round-to-nearest rule also implies overflow and 379 * underflow behaviour; if the exact value of {@code s} is large 380 * enough in magnitude (greater than or equal to ({@link 381 * #MAX_VALUE} + {@link Math#ulp(float) ulp(MAX_VALUE)}/2), 382 * rounding to {@code float} will result in an infinity and if the 383 * exact value of {@code s} is small enough in magnitude (less 384 * than or equal to {@link #MIN_VALUE}/2), rounding to float will 385 * result in a zero. 386 * 387 * Finally, after rounding a {@code Float} object representing 388 * this {@code float} value is returned. 389 * 390 * <p>To interpret localized string representations of a 391 * floating-point value, use subclasses of {@link 392 * java.text.NumberFormat}. 393 * 394 * <p>Note that trailing format specifiers, specifiers that 395 * determine the type of a floating-point literal 396 * ({@code 1.0f} is a {@code float} value; 397 * {@code 1.0d} is a {@code double} value), do 398 * <em>not</em> influence the results of this method. In other 399 * words, the numerical value of the input string is converted 400 * directly to the target floating-point type. In general, the 401 * two-step sequence of conversions, string to {@code double} 402 * followed by {@code double} to {@code float}, is 403 * <em>not</em> equivalent to converting a string directly to 404 * {@code float}. For example, if first converted to an 405 * intermediate {@code double} and then to 406 * {@code float}, the string<br> 407 * {@code "1.00000017881393421514957253748434595763683319091796875001d"}<br> 408 * results in the {@code float} value 409 * {@code 1.0000002f}; if the string is converted directly to 410 * {@code float}, <code>1.000000<b>1</b>f</code> results. 411 * 412 * <p>To avoid calling this method on an invalid string and having 413 * a {@code NumberFormatException} be thrown, the documentation 414 * for {@link Double#valueOf Double.valueOf} lists a regular 415 * expression which can be used to screen the input. 416 * 417 * @param s the string to be parsed. 418 * @return a {@code Float} object holding the value 419 * represented by the {@code String} argument. 420 * @throws NumberFormatException if the string does not contain a 421 * parsable number. 422 */ 423 public static Float valueOf(String s) throws NumberFormatException { 424 return new Float(FloatingDecimal.getThreadLocalInstance().readJavaFormatString(s).floatValue()); 425 } 426 427 /** 428 * Returns a {@code Float} instance representing the specified 429 * {@code float} value. 430 * If a new {@code Float} instance is not required, this method 431 * should generally be used in preference to the constructor 432 * {@link #Float(float)}, as this method is likely to yield 433 * significantly better space and time performance by caching 434 * frequently requested values. 435 * 436 * @param f a float value. 437 * @return a {@code Float} instance representing {@code f}. 438 * @since 1.5 439 */ 440 public static Float valueOf(float f) { 441 return new Float(f); 442 } 443 444 /** 445 * Returns a new {@code float} initialized to the value 446 * represented by the specified {@code String}, as performed 447 * by the {@code valueOf} method of class {@code Float}. 448 * 449 * @param s the string to be parsed. 450 * @return the {@code float} value represented by the string 451 * argument. 452 * @throws NullPointerException if the string is null 453 * @throws NumberFormatException if the string does not contain a 454 * parsable {@code float}. 455 * @see java.lang.Float#valueOf(String) 456 * @since 1.2 457 */ 458 public static float parseFloat(String s) throws NumberFormatException { 459 return FloatingDecimal.getThreadLocalInstance().readJavaFormatString(s).floatValue(); 460 } 461 462 /** 463 * Returns {@code true} if the specified number is a 464 * Not-a-Number (NaN) value, {@code false} otherwise. 465 * 466 * @param v the value to be tested. 467 * @return {@code true} if the argument is NaN; 468 * {@code false} otherwise. 469 */ 470 static public boolean isNaN(float v) { 471 return (v != v); 472 } 473 474 /** 475 * Returns {@code true} if the specified number is infinitely 476 * large in magnitude, {@code false} otherwise. 477 * 478 * @param v the value to be tested. 479 * @return {@code true} if the argument is positive infinity or 480 * negative infinity; {@code false} otherwise. 481 */ 482 static public boolean isInfinite(float v) { 483 return (v == POSITIVE_INFINITY) || (v == NEGATIVE_INFINITY); 484 } 485 486 /** 487 * Returns {@code true} if the argument is a finite floating-point 488 * value; returns {@code false} otherwise (for NaN and infinity 489 * arguments). 490 * 491 * @param f the {@code float} value to be tested 492 * @return {@code true} if the argument is a finite 493 * floating-point value, {@code false} otherwise. 494 * @since 1.8 495 */ 496 public static boolean isFinite(float f) { 497 return Math.abs(f) <= FloatConsts.MAX_VALUE; 498 } 499 500 /** 501 * The value of the Float. 502 * 503 * @serial 504 */ 505 private final float value; 506 507 /** 508 * Constructs a newly allocated {@code Float} object that 509 * represents the primitive {@code float} argument. 510 * 511 * @param value the value to be represented by the {@code Float}. 512 */ 513 public Float(float value) { 514 this.value = value; 515 } 516 517 /** 518 * Constructs a newly allocated {@code Float} object that 519 * represents the argument converted to type {@code float}. 520 * 521 * @param value the value to be represented by the {@code Float}. 522 */ 523 public Float(double value) { 524 this.value = (float)value; 525 } 526 527 /** 528 * Constructs a newly allocated {@code Float} object that 529 * represents the floating-point value of type {@code float} 530 * represented by the string. The string is converted to a 531 * {@code float} value as if by the {@code valueOf} method. 532 * 533 * @param s a string to be converted to a {@code Float}. 534 * @throws NumberFormatException if the string does not contain a 535 * parsable number. 536 * @see java.lang.Float#valueOf(java.lang.String) 537 */ 538 public Float(String s) throws NumberFormatException { 539 // REMIND: this is inefficient 540 this(valueOf(s).floatValue()); 541 } 542 543 /** 544 * Returns {@code true} if this {@code Float} value is a 545 * Not-a-Number (NaN), {@code false} otherwise. 546 * 547 * @return {@code true} if the value represented by this object is 548 * NaN; {@code false} otherwise. 549 */ 550 public boolean isNaN() { 551 return isNaN(value); 552 } 553 554 /** 555 * Returns {@code true} if this {@code Float} value is 556 * infinitely large in magnitude, {@code false} otherwise. 557 * 558 * @return {@code true} if the value represented by this object is 559 * positive infinity or negative infinity; 560 * {@code false} otherwise. 561 */ 562 public boolean isInfinite() { 563 return isInfinite(value); 564 } 565 566 /** 567 * Returns a string representation of this {@code Float} object. 568 * The primitive {@code float} value represented by this object 569 * is converted to a {@code String} exactly as if by the method 570 * {@code toString} of one argument. 571 * 572 * @return a {@code String} representation of this object. 573 * @see java.lang.Float#toString(float) 574 */ 575 public String toString() { 576 return Float.toString(value); 577 } 578 579 /** 580 * Returns the value of this {@code Float} as a {@code byte} (by 581 * casting to a {@code byte}). 582 * 583 * @return the {@code float} value represented by this object 584 * converted to type {@code byte} 585 */ 586 public byte byteValue() { 587 return (byte)value; 588 } 589 590 /** 591 * Returns the value of this {@code Float} as a {@code short} (by 592 * casting to a {@code short}). 593 * 594 * @return the {@code float} value represented by this object 595 * converted to type {@code short} 596 * @since JDK1.1 597 */ 598 public short shortValue() { 599 return (short)value; 600 } 601 602 /** 603 * Returns the value of this {@code Float} as an {@code int} (by 604 * casting to type {@code int}). 605 * 606 * @return the {@code float} value represented by this object 607 * converted to type {@code int} 608 */ 609 public int intValue() { 610 return (int)value; 611 } 612 613 /** 614 * Returns value of this {@code Float} as a {@code long} (by 615 * casting to type {@code long}). 616 * 617 * @return the {@code float} value represented by this object 618 * converted to type {@code long} 619 */ 620 public long longValue() { 621 return (long)value; 622 } 623 624 /** 625 * Returns the {@code float} value of this {@code Float} object. 626 * 627 * @return the {@code float} value represented by this object 628 */ 629 public float floatValue() { 630 return value; 631 } 632 633 /** 634 * Returns the {@code double} value of this {@code Float} object. 635 * 636 * @return the {@code float} value represented by this 637 * object is converted to type {@code double} and the 638 * result of the conversion is returned. 639 */ 640 public double doubleValue() { 641 return (double)value; 642 } 643 644 /** 645 * Returns a hash code for this {@code Float} object. The 646 * result is the integer bit representation, exactly as produced 647 * by the method {@link #floatToIntBits(float)}, of the primitive 648 * {@code float} value represented by this {@code Float} 649 * object. 650 * 651 * @return a hash code value for this object. 652 */ 653 public int hashCode() { 654 return floatToIntBits(value); 655 } 656 657 /** 658 * Returns a hash code for a {@code float} value; compatible with 659 * {@code Float.hashCode()}. 660 * 661 * @param value the value to hash 662 * @return a hash code value for a {@code float} value. 663 * @since 1.8 664 */ 665 public static int hashCode(float value) { 666 return floatToIntBits(value); 667 } 668 669 /** 670 671 * Compares this object against the specified object. The result 672 * is {@code true} if and only if the argument is not 673 * {@code null} and is a {@code Float} object that 674 * represents a {@code float} with the same value as the 675 * {@code float} represented by this object. For this 676 * purpose, two {@code float} values are considered to be the 677 * same if and only if the method {@link #floatToIntBits(float)} 678 * returns the identical {@code int} value when applied to 679 * each. 680 * 681 * <p>Note that in most cases, for two instances of class 682 * {@code Float}, {@code f1} and {@code f2}, the value 683 * of {@code f1.equals(f2)} is {@code true} if and only if 684 * 685 * <blockquote><pre> 686 * f1.floatValue() == f2.floatValue() 687 * </pre></blockquote> 688 * 689 * <p>also has the value {@code true}. However, there are two exceptions: 690 * <ul> 691 * <li>If {@code f1} and {@code f2} both represent 692 * {@code Float.NaN}, then the {@code equals} method returns 693 * {@code true}, even though {@code Float.NaN==Float.NaN} 694 * has the value {@code false}. 695 * <li>If {@code f1} represents {@code +0.0f} while 696 * {@code f2} represents {@code -0.0f}, or vice 697 * versa, the {@code equal} test has the value 698 * {@code false}, even though {@code 0.0f==-0.0f} 699 * has the value {@code true}. 700 * </ul> 701 * 702 * This definition allows hash tables to operate properly. 703 * 704 * @param obj the object to be compared 705 * @return {@code true} if the objects are the same; 706 * {@code false} otherwise. 707 * @see java.lang.Float#floatToIntBits(float) 708 */ 709 public boolean equals(Object obj) { 710 return (obj instanceof Float) 711 && (floatToIntBits(((Float)obj).value) == floatToIntBits(value)); 712 } 713 714 /** 715 * Returns a representation of the specified floating-point value 716 * according to the IEEE 754 floating-point "single format" bit 717 * layout. 718 * 719 * <p>Bit 31 (the bit that is selected by the mask 720 * {@code 0x80000000}) represents the sign of the floating-point 721 * number. 722 * Bits 30-23 (the bits that are selected by the mask 723 * {@code 0x7f800000}) represent the exponent. 724 * Bits 22-0 (the bits that are selected by the mask 725 * {@code 0x007fffff}) represent the significand (sometimes called 726 * the mantissa) of the floating-point number. 727 * 728 * <p>If the argument is positive infinity, the result is 729 * {@code 0x7f800000}. 730 * 731 * <p>If the argument is negative infinity, the result is 732 * {@code 0xff800000}. 733 * 734 * <p>If the argument is NaN, the result is {@code 0x7fc00000}. 735 * 736 * <p>In all cases, the result is an integer that, when given to the 737 * {@link #intBitsToFloat(int)} method, will produce a floating-point 738 * value the same as the argument to {@code floatToIntBits} 739 * (except all NaN values are collapsed to a single 740 * "canonical" NaN value). 741 * 742 * @param value a floating-point number. 743 * @return the bits that represent the floating-point number. 744 */ 745 public static int floatToIntBits(float value) { 746 int result = floatToRawIntBits(value); 747 // Check for NaN based on values of bit fields, maximum 748 // exponent and nonzero significand. 749 if ( ((result & FloatConsts.EXP_BIT_MASK) == 750 FloatConsts.EXP_BIT_MASK) && 751 (result & FloatConsts.SIGNIF_BIT_MASK) != 0) 752 result = 0x7fc00000; 753 return result; 754 } 755 756 /** 757 * Returns a representation of the specified floating-point value 758 * according to the IEEE 754 floating-point "single format" bit 759 * layout, preserving Not-a-Number (NaN) values. 760 * 761 * <p>Bit 31 (the bit that is selected by the mask 762 * {@code 0x80000000}) represents the sign of the floating-point 763 * number. 764 * Bits 30-23 (the bits that are selected by the mask 765 * {@code 0x7f800000}) represent the exponent. 766 * Bits 22-0 (the bits that are selected by the mask 767 * {@code 0x007fffff}) represent the significand (sometimes called 768 * the mantissa) of the floating-point number. 769 * 770 * <p>If the argument is positive infinity, the result is 771 * {@code 0x7f800000}. 772 * 773 * <p>If the argument is negative infinity, the result is 774 * {@code 0xff800000}. 775 * 776 * <p>If the argument is NaN, the result is the integer representing 777 * the actual NaN value. Unlike the {@code floatToIntBits} 778 * method, {@code floatToRawIntBits} does not collapse all the 779 * bit patterns encoding a NaN to a single "canonical" 780 * NaN value. 781 * 782 * <p>In all cases, the result is an integer that, when given to the 783 * {@link #intBitsToFloat(int)} method, will produce a 784 * floating-point value the same as the argument to 785 * {@code floatToRawIntBits}. 786 * 787 * @param value a floating-point number. 788 * @return the bits that represent the floating-point number. 789 * @since 1.3 790 */ 791 public static native int floatToRawIntBits(float value); 792 793 /** 794 * Returns the {@code float} value corresponding to a given 795 * bit representation. 796 * The argument is considered to be a representation of a 797 * floating-point value according to the IEEE 754 floating-point 798 * "single format" bit layout. 799 * 800 * <p>If the argument is {@code 0x7f800000}, the result is positive 801 * infinity. 802 * 803 * <p>If the argument is {@code 0xff800000}, the result is negative 804 * infinity. 805 * 806 * <p>If the argument is any value in the range 807 * {@code 0x7f800001} through {@code 0x7fffffff} or in 808 * the range {@code 0xff800001} through 809 * {@code 0xffffffff}, the result is a NaN. No IEEE 754 810 * floating-point operation provided by Java can distinguish 811 * between two NaN values of the same type with different bit 812 * patterns. Distinct values of NaN are only distinguishable by 813 * use of the {@code Float.floatToRawIntBits} method. 814 * 815 * <p>In all other cases, let <i>s</i>, <i>e</i>, and <i>m</i> be three 816 * values that can be computed from the argument: 817 * 818 * <blockquote><pre> 819 * int s = ((bits >> 31) == 0) ? 1 : -1; 820 * int e = ((bits >> 23) & 0xff); 821 * int m = (e == 0) ? 822 * (bits & 0x7fffff) << 1 : 823 * (bits & 0x7fffff) | 0x800000; 824 * </pre></blockquote> 825 * 826 * Then the floating-point result equals the value of the mathematical 827 * expression <i>s</i>·<i>m</i>·2<sup><i>e</i>-150</sup>. 828 * 829 * <p>Note that this method may not be able to return a 830 * {@code float} NaN with exactly same bit pattern as the 831 * {@code int} argument. IEEE 754 distinguishes between two 832 * kinds of NaNs, quiet NaNs and <i>signaling NaNs</i>. The 833 * differences between the two kinds of NaN are generally not 834 * visible in Java. Arithmetic operations on signaling NaNs turn 835 * them into quiet NaNs with a different, but often similar, bit 836 * pattern. However, on some processors merely copying a 837 * signaling NaN also performs that conversion. In particular, 838 * copying a signaling NaN to return it to the calling method may 839 * perform this conversion. So {@code intBitsToFloat} may 840 * not be able to return a {@code float} with a signaling NaN 841 * bit pattern. Consequently, for some {@code int} values, 842 * {@code floatToRawIntBits(intBitsToFloat(start))} may 843 * <i>not</i> equal {@code start}. Moreover, which 844 * particular bit patterns represent signaling NaNs is platform 845 * dependent; although all NaN bit patterns, quiet or signaling, 846 * must be in the NaN range identified above. 847 * 848 * @param bits an integer. 849 * @return the {@code float} floating-point value with the same bit 850 * pattern. 851 */ 852 public static native float intBitsToFloat(int bits); 853 854 /** 855 * Compares two {@code Float} objects numerically. There are 856 * two ways in which comparisons performed by this method differ 857 * from those performed by the Java language numerical comparison 858 * operators ({@code <, <=, ==, >=, >}) when 859 * applied to primitive {@code float} values: 860 * 861 * <ul><li> 862 * {@code Float.NaN} is considered by this method to 863 * be equal to itself and greater than all other 864 * {@code float} values 865 * (including {@code Float.POSITIVE_INFINITY}). 866 * <li> 867 * {@code 0.0f} is considered by this method to be greater 868 * than {@code -0.0f}. 869 * </ul> 870 * 871 * This ensures that the <i>natural ordering</i> of {@code Float} 872 * objects imposed by this method is <i>consistent with equals</i>. 873 * 874 * @param anotherFloat the {@code Float} to be compared. 875 * @return the value {@code 0} if {@code anotherFloat} is 876 * numerically equal to this {@code Float}; a value 877 * less than {@code 0} if this {@code Float} 878 * is numerically less than {@code anotherFloat}; 879 * and a value greater than {@code 0} if this 880 * {@code Float} is numerically greater than 881 * {@code anotherFloat}. 882 * 883 * @since 1.2 884 * @see Comparable#compareTo(Object) 885 */ 886 public int compareTo(Float anotherFloat) { 887 return Float.compare(value, anotherFloat.value); 888 } 889 890 /** 891 * Compares the two specified {@code float} values. The sign 892 * of the integer value returned is the same as that of the 893 * integer that would be returned by the call: 894 * <pre> 895 * new Float(f1).compareTo(new Float(f2)) 896 * </pre> 897 * 898 * @param f1 the first {@code float} to compare. 899 * @param f2 the second {@code float} to compare. 900 * @return the value {@code 0} if {@code f1} is 901 * numerically equal to {@code f2}; a value less than 902 * {@code 0} if {@code f1} is numerically less than 903 * {@code f2}; and a value greater than {@code 0} 904 * if {@code f1} is numerically greater than 905 * {@code f2}. 906 * @since 1.4 907 */ 908 public static int compare(float f1, float f2) { 909 if (f1 < f2) 910 return -1; // Neither val is NaN, thisVal is smaller 911 if (f1 > f2) 912 return 1; // Neither val is NaN, thisVal is larger 913 914 // Cannot use floatToRawIntBits because of possibility of NaNs. 915 int thisBits = Float.floatToIntBits(f1); 916 int anotherBits = Float.floatToIntBits(f2); 917 918 return (thisBits == anotherBits ? 0 : // Values are equal 919 (thisBits < anotherBits ? -1 : // (-0.0, 0.0) or (!NaN, NaN) 920 1)); // (0.0, -0.0) or (NaN, !NaN) 921 } 922 923 /** 924 * Adds two {@code float} values together as per the + operator. 925 * 926 * @param a the first operand 927 * @param b the second operand 928 * @return the sum of {@code a} and {@code b} 929 * @jls 4.2.4 Floating-Point Operations 930 * @see java.util.function.BinaryOperator 931 * @since 1.8 932 */ 933 public static float sum(float a, float b) { 934 return a + b; 935 } 936 937 /** 938 * Returns the greater of two {@code float} values 939 * as if by calling {@link Math#max(float, float) Math.max}. 940 * 941 * @param a the first operand 942 * @param b the second operand 943 * @return the greater of {@code a} and {@code b} 944 * @see java.util.function.BinaryOperator 945 * @since 1.8 946 */ 947 public static float max(float a, float b) { 948 return Math.max(a, b); 949 } 950 951 /** 952 * Returns the smaller of two {@code float} values 953 * as if by calling {@link Math#min(float, float) Math.min}. 954 * 955 * @param a the first operand 956 * @param b the second operand 957 * @return the smaller of {@code a} and {@code b} 958 * @see java.util.function.BinaryOperator 959 * @since 1.8 960 */ 961 public static float min(float a, float b) { 962 return Math.min(a, b); 963 } 964 965 /** use serialVersionUID from JDK 1.0.2 for interoperability */ 966 private static final long serialVersionUID = -2671257302660747028L; 967} 968