1 /* 2 * Copyright (c) 1994, 2011, 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 package java.lang; 27 28 import sun.misc.FloatingDecimal; 29 import sun.misc.FloatConsts; 30 import sun.misc.DoubleConsts; 31 32 /** 33 * The {@code Float} class wraps a value of primitive type 34 * {@code float} in an object. An object of type 35 * {@code Float} contains a single field whose type is 36 * {@code float}. 37 * 38 * <p>In addition, this class provides several methods for converting a 39 * {@code float} to a {@code String} and a 40 * {@code String} to a {@code float}, as well as other 41 * constants and methods useful when dealing with a 42 * {@code float}. 43 * 44 * @author Lee Boynton 45 * @author Arthur van Hoff 46 * @author Joseph D. Darcy 47 * @since JDK1.0 48 */ 49 public final class Float extends Number implements Comparable<Float> { 50 /** 51 * A constant holding the positive infinity of type 52 * {@code float}. It is equal to the value returned by 53 * {@code Float.intBitsToFloat(0x7f800000)}. 54 */ 55 public static final float POSITIVE_INFINITY = 1.0f / 0.0f; 56 57 /** 58 * A constant holding the negative infinity of type 59 * {@code float}. It is equal to the value returned by 60 * {@code Float.intBitsToFloat(0xff800000)}. 61 */ 62 public static final float NEGATIVE_INFINITY = -1.0f / 0.0f; 63 64 /** 65 * A constant holding a Not-a-Number (NaN) value of type 66 * {@code float}. It is equivalent to the value returned by 67 * {@code Float.intBitsToFloat(0x7fc00000)}. 68 */ 69 public static final float NaN = 0.0f / 0.0f; 70 71 /** 72 * A constant holding the largest positive finite value of type 73 * {@code float}, (2-2<sup>-23</sup>)·2<sup>127</sup>. 74 * It is equal to the hexadecimal floating-point literal 75 * {@code 0x1.fffffeP+127f} and also equal to 76 * {@code Float.intBitsToFloat(0x7f7fffff)}. 77 */ 78 public static final float MAX_VALUE = 0x1.fffffeP+127f; // 3.4028235e+38f 79 80 /** 81 * A constant holding the smallest positive normal value of type 82 * {@code float}, 2<sup>-126</sup>. It is equal to the 83 * hexadecimal floating-point literal {@code 0x1.0p-126f} and also 84 * equal to {@code Float.intBitsToFloat(0x00800000)}. 85 * 86 * @since 1.6 87 */ 88 public static final float MIN_NORMAL = 0x1.0p-126f; // 1.17549435E-38f 89 90 /** 91 * A constant holding the smallest positive nonzero value of type 92 * {@code float}, 2<sup>-149</sup>. It is equal to the 93 * hexadecimal floating-point literal {@code 0x0.000002P-126f} 94 * and also equal to {@code Float.intBitsToFloat(0x1)}. 95 */ 96 public static final float MIN_VALUE = 0x0.000002P-126f; // 1.4e-45f 97 98 /** 99 * Maximum exponent a finite {@code float} variable may have. It 100 * is equal to the value returned by {@code 101 * Math.getExponent(Float.MAX_VALUE)}. 102 * 103 * @since 1.6 104 */ 105 public static final int MAX_EXPONENT = 127; 106 107 /** 108 * Minimum exponent a normalized {@code float} variable may have. 109 * It is equal to the value returned by {@code 110 * Math.getExponent(Float.MIN_NORMAL)}. 111 * 112 * @since 1.6 113 */ 114 public static final int MIN_EXPONENT = -126; 115 116 /** 117 * The number of bits used to represent a {@code float} value. 118 * 119 * @since 1.5 120 */ 121 public static final int SIZE = 32; 122 123 /** 124 * The number of bytes used to represent a {@code float} value. 125 * 126 * @since 1.8 127 */ 128 public static final int BYTES = SIZE / Byte.SIZE; 129 130 /** 131 * The {@code Class} instance representing the primitive type 132 * {@code float}. 133 * 134 * @since JDK1.1 135 */ 136 public static final Class<Float> TYPE = Class.getPrimitiveClass("float"); 137 138 /** 139 * Returns a string representation of the {@code float} 140 * argument. All characters mentioned below are ASCII characters. 141 * <ul> 142 * <li>If the argument is NaN, the result is the string 143 * "{@code NaN}". 144 * <li>Otherwise, the result is a string that represents the sign and 145 * magnitude (absolute value) of the argument. If the sign is 146 * negative, the first character of the result is 147 * '{@code -}' (<code>'\u002D'</code>); if the sign is 148 * positive, no sign character appears in the result. As for 149 * the magnitude <i>m</i>: 150 * <ul> 151 * <li>If <i>m</i> is infinity, it is represented by the characters 152 * {@code "Infinity"}; thus, positive infinity produces 153 * the result {@code "Infinity"} and negative infinity 154 * produces the result {@code "-Infinity"}. 155 * <li>If <i>m</i> is zero, it is represented by the characters 156 * {@code "0.0"}; thus, negative zero produces the result 157 * {@code "-0.0"} and positive zero produces the result 158 * {@code "0.0"}. 159 * <li> If <i>m</i> is greater than or equal to 10<sup>-3</sup> but 160 * less than 10<sup>7</sup>, then it is represented as the 161 * integer part of <i>m</i>, in decimal form with no leading 162 * zeroes, followed by '{@code .}' 163 * (<code>'\u002E'</code>), followed by one or more 164 * decimal digits representing the fractional part of 165 * <i>m</i>. 166 * <li> If <i>m</i> is less than 10<sup>-3</sup> or greater than or 167 * equal to 10<sup>7</sup>, then it is represented in 168 * so-called "computerized scientific notation." Let <i>n</i> 169 * be the unique integer such that 10<sup><i>n</i> </sup>≤ 170 * <i>m</i> {@literal <} 10<sup><i>n</i>+1</sup>; then let <i>a</i> 171 * be the mathematically exact quotient of <i>m</i> and 172 * 10<sup><i>n</i></sup> so that 1 ≤ <i>a</i> {@literal <} 10. 173 * The magnitude is then represented as the integer part of 174 * <i>a</i>, as a single decimal digit, followed by 175 * '{@code .}' (<code>'\u002E'</code>), followed by 176 * decimal digits representing the fractional part of 177 * <i>a</i>, followed by the letter '{@code E}' 178 * (<code>'\u0045'</code>), followed by a representation 179 * of <i>n</i> as a decimal integer, as produced by the 180 * method {@link java.lang.Integer#toString(int)}. 181 * 182 * </ul> 183 * </ul> 184 * How many digits must be printed for the fractional part of 185 * <i>m</i> or <i>a</i>? There must be at least one digit 186 * to represent the fractional part, and beyond that as many, but 187 * only as many, more digits as are needed to uniquely distinguish 188 * the argument value from adjacent values of type 189 * {@code float}. That is, suppose that <i>x</i> is the 190 * exact mathematical value represented by the decimal 191 * representation produced by this method for a finite nonzero 192 * argument <i>f</i>. Then <i>f</i> must be the {@code float} 193 * value nearest to <i>x</i>; or, if two {@code float} values are 194 * equally close to <i>x</i>, then <i>f</i> must be one of 195 * them and the least significant bit of the significand of 196 * <i>f</i> must be {@code 0}. 197 * 198 * <p>To create localized string representations of a floating-point 199 * value, use subclasses of {@link java.text.NumberFormat}. 200 * 201 * @param f the float to be converted. 202 * @return a string representation of the argument. 203 */ 204 public static String toString(float f) { 205 return new FloatingDecimal(f).toJavaFormatString(); 206 } 207 208 /** 209 * Returns a hexadecimal string representation of the 210 * {@code float} argument. All characters mentioned below are 211 * ASCII characters. 212 * 213 * <ul> 214 * <li>If the argument is NaN, the result is the string 215 * "{@code NaN}". 216 * <li>Otherwise, the result is a string that represents the sign and 217 * magnitude (absolute value) of the argument. If the sign is negative, 218 * the first character of the result is '{@code -}' 219 * (<code>'\u002D'</code>); if the sign is positive, no sign character 220 * appears in the result. As for the magnitude <i>m</i>: 221 * 222 * <ul> 223 * <li>If <i>m</i> is infinity, it is represented by the string 224 * {@code "Infinity"}; thus, positive infinity produces the 225 * result {@code "Infinity"} and negative infinity produces 226 * the result {@code "-Infinity"}. 227 * 228 * <li>If <i>m</i> is zero, it is represented by the string 229 * {@code "0x0.0p0"}; thus, negative zero produces the result 230 * {@code "-0x0.0p0"} and positive zero produces the result 231 * {@code "0x0.0p0"}. 232 * 233 * <li>If <i>m</i> is a {@code float} value with a 234 * normalized representation, substrings are used to represent the 235 * significand and exponent fields. The significand is 236 * represented by the characters {@code "0x1."} 237 * followed by a lowercase hexadecimal representation of the rest 238 * of the significand as a fraction. Trailing zeros in the 239 * hexadecimal representation are removed unless all the digits 240 * are zero, in which case a single zero is used. Next, the 241 * exponent is represented by {@code "p"} followed 242 * by a decimal string of the unbiased exponent as if produced by 243 * a call to {@link Integer#toString(int) Integer.toString} on the 244 * exponent value. 245 * 246 * <li>If <i>m</i> is a {@code float} value with a subnormal 247 * representation, the significand is represented by the 248 * characters {@code "0x0."} followed by a 249 * hexadecimal representation of the rest of the significand as a 250 * fraction. Trailing zeros in the hexadecimal representation are 251 * removed. Next, the exponent is represented by 252 * {@code "p-126"}. Note that there must be at 253 * least one nonzero digit in a subnormal significand. 254 * 255 * </ul> 256 * 257 * </ul> 258 * 259 * <table border> 260 * <caption><h3>Examples</h3></caption> 261 * <tr><th>Floating-point Value</th><th>Hexadecimal String</th> 262 * <tr><td>{@code 1.0}</td> <td>{@code 0x1.0p0}</td> 263 * <tr><td>{@code -1.0}</td> <td>{@code -0x1.0p0}</td> 264 * <tr><td>{@code 2.0}</td> <td>{@code 0x1.0p1}</td> 265 * <tr><td>{@code 3.0}</td> <td>{@code 0x1.8p1}</td> 266 * <tr><td>{@code 0.5}</td> <td>{@code 0x1.0p-1}</td> 267 * <tr><td>{@code 0.25}</td> <td>{@code 0x1.0p-2}</td> 268 * <tr><td>{@code Float.MAX_VALUE}</td> 269 * <td>{@code 0x1.fffffep127}</td> 270 * <tr><td>{@code Minimum Normal Value}</td> 271 * <td>{@code 0x1.0p-126}</td> 272 * <tr><td>{@code Maximum Subnormal Value}</td> 273 * <td>{@code 0x0.fffffep-126}</td> 274 * <tr><td>{@code Float.MIN_VALUE}</td> 275 * <td>{@code 0x0.000002p-126}</td> 276 * </table> 277 * @param f the {@code float} to be converted. 278 * @return a hex string representation of the argument. 279 * @since 1.5 280 * @author Joseph D. Darcy 281 */ 282 public static String toHexString(float f) { 283 if (Math.abs(f) < FloatConsts.MIN_NORMAL 284 && f != 0.0f ) {// float subnormal 285 // Adjust exponent to create subnormal double, then 286 // replace subnormal double exponent with subnormal float 287 // exponent 288 String s = Double.toHexString(Math.scalb((double)f, 289 /* -1022+126 */ 290 DoubleConsts.MIN_EXPONENT- 291 FloatConsts.MIN_EXPONENT)); 292 return s.replaceFirst("p-1022$", "p-126"); 293 } 294 else // double string will be the same as float string 295 return Double.toHexString(f); 296 } 297 298 /** 299 * Returns a {@code Float} object holding the 300 * {@code float} value represented by the argument string 301 * {@code s}. 302 * 303 * <p>If {@code s} is {@code null}, then a 304 * {@code NullPointerException} is thrown. 305 * 306 * <p>Leading and trailing whitespace characters in {@code s} 307 * are ignored. Whitespace is removed as if by the {@link 308 * String#trim} method; that is, both ASCII space and control 309 * characters are removed. The rest of {@code s} should 310 * constitute a <i>FloatValue</i> as described by the lexical 311 * syntax rules: 312 * 313 * <blockquote> 314 * <dl> 315 * <dt><i>FloatValue:</i> 316 * <dd><i>Sign<sub>opt</sub></i> {@code NaN} 317 * <dd><i>Sign<sub>opt</sub></i> {@code Infinity} 318 * <dd><i>Sign<sub>opt</sub> FloatingPointLiteral</i> 319 * <dd><i>Sign<sub>opt</sub> HexFloatingPointLiteral</i> 320 * <dd><i>SignedInteger</i> 321 * </dl> 322 * 323 * <p> 324 * 325 * <dl> 326 * <dt><i>HexFloatingPointLiteral</i>: 327 * <dd> <i>HexSignificand BinaryExponent FloatTypeSuffix<sub>opt</sub></i> 328 * </dl> 329 * 330 * <p> 331 * 332 * <dl> 333 * <dt><i>HexSignificand:</i> 334 * <dd><i>HexNumeral</i> 335 * <dd><i>HexNumeral</i> {@code .} 336 * <dd>{@code 0x} <i>HexDigits<sub>opt</sub> 337 * </i>{@code .}<i> HexDigits</i> 338 * <dd>{@code 0X}<i> HexDigits<sub>opt</sub> 339 * </i>{@code .} <i>HexDigits</i> 340 * </dl> 341 * 342 * <p> 343 * 344 * <dl> 345 * <dt><i>BinaryExponent:</i> 346 * <dd><i>BinaryExponentIndicator SignedInteger</i> 347 * </dl> 348 * 349 * <p> 350 * 351 * <dl> 352 * <dt><i>BinaryExponentIndicator:</i> 353 * <dd>{@code p} 354 * <dd>{@code P} 355 * </dl> 356 * 357 * </blockquote> 358 * 359 * where <i>Sign</i>, <i>FloatingPointLiteral</i>, 360 * <i>HexNumeral</i>, <i>HexDigits</i>, <i>SignedInteger</i> and 361 * <i>FloatTypeSuffix</i> are as defined in the lexical structure 362 * sections of 363 * <cite>The Java™ Language Specification</cite>, 364 * except that underscores are not accepted between digits. 365 * If {@code s} does not have the form of 366 * a <i>FloatValue</i>, then a {@code NumberFormatException} 367 * is thrown. Otherwise, {@code s} is regarded as 368 * representing an exact decimal value in the usual 369 * "computerized scientific notation" or as an exact 370 * hexadecimal value; this exact numerical value is then 371 * conceptually converted to an "infinitely precise" 372 * binary value that is then rounded to type {@code float} 373 * by the usual round-to-nearest rule of IEEE 754 floating-point 374 * arithmetic, which includes preserving the sign of a zero 375 * value. 376 * 377 * Note that the round-to-nearest rule also implies overflow and 378 * underflow behaviour; if the exact value of {@code s} is large 379 * enough in magnitude (greater than or equal to ({@link 380 * #MAX_VALUE} + {@link Math#ulp(float) ulp(MAX_VALUE)}/2), 381 * rounding to {@code float} will result in an infinity and if the 382 * exact value of {@code s} is small enough in magnitude (less 383 * than or equal to {@link #MIN_VALUE}/2), rounding to float will 384 * result in a zero. 385 * 386 * Finally, after rounding a {@code Float} object representing 387 * this {@code float} value is returned. 388 * 389 * <p>To interpret localized string representations of a 390 * floating-point value, use subclasses of {@link 391 * java.text.NumberFormat}. 392 * 393 * <p>Note that trailing format specifiers, specifiers that 394 * determine the type of a floating-point literal 395 * ({@code 1.0f} is a {@code float} value; 396 * {@code 1.0d} is a {@code double} value), do 397 * <em>not</em> influence the results of this method. In other 398 * words, the numerical value of the input string is converted 399 * directly to the target floating-point type. In general, the 400 * two-step sequence of conversions, string to {@code double} 401 * followed by {@code double} to {@code float}, is 402 * <em>not</em> equivalent to converting a string directly to 403 * {@code float}. For example, if first converted to an 404 * intermediate {@code double} and then to 405 * {@code float}, the string<br> 406 * {@code "1.00000017881393421514957253748434595763683319091796875001d"}<br> 407 * results in the {@code float} value 408 * {@code 1.0000002f}; if the string is converted directly to 409 * {@code float}, <code>1.000000<b>1</b>f</code> results. 410 * 411 * <p>To avoid calling this method on an invalid string and having 412 * a {@code NumberFormatException} be thrown, the documentation 413 * for {@link Double#valueOf Double.valueOf} lists a regular 414 * expression which can be used to screen the input. 415 * 416 * @param s the string to be parsed. 417 * @return a {@code Float} object holding the value 418 * represented by the {@code String} argument. 419 * @throws NumberFormatException if the string does not contain a 420 * parsable number. 421 */ 422 public static Float valueOf(String s) throws NumberFormatException { 423 return new Float(FloatingDecimal.readJavaFormatString(s).floatValue()); 424 } 425 426 /** 427 * Returns a {@code Float} instance representing the specified 428 * {@code float} value. 429 * If a new {@code Float} instance is not required, this method 430 * should generally be used in preference to the constructor 431 * {@link #Float(float)}, as this method is likely to yield 432 * significantly better space and time performance by caching 433 * frequently requested values. 434 * 435 * @param f a float value. 436 * @return a {@code Float} instance representing {@code f}. 437 * @since 1.5 438 */ 439 public static Float valueOf(float f) { 440 return new Float(f); 441 } 442 443 /** 444 * Returns a new {@code float} initialized to the value 445 * represented by the specified {@code String}, as performed 446 * by the {@code valueOf} method of class {@code Float}. 447 * 448 * @param s the string to be parsed. 449 * @return the {@code float} value represented by the string 450 * argument. 451 * @throws NullPointerException if the string is null 452 * @throws NumberFormatException if the string does not contain a 453 * parsable {@code float}. 454 * @see java.lang.Float#valueOf(String) 455 * @since 1.2 456 */ 457 public static float parseFloat(String s) throws NumberFormatException { 458 return FloatingDecimal.readJavaFormatString(s).floatValue(); 459 } 460 461 /** 462 * Returns {@code true} if the specified number is a 463 * Not-a-Number (NaN) value, {@code false} otherwise. 464 * 465 * @param v the value to be tested. 466 * @return {@code true} if the argument is NaN; 467 * {@code false} otherwise. 468 */ 469 static public boolean isNaN(float v) { 470 return (v != v); 471 } 472 473 /** 474 * Returns {@code true} if the specified number is infinitely 475 * large in magnitude, {@code false} otherwise. 476 * 477 * @param v the value to be tested. 478 * @return {@code true} if the argument is positive infinity or 479 * negative infinity; {@code false} otherwise. 480 */ 481 static public boolean isInfinite(float v) { 482 return (v == POSITIVE_INFINITY) || (v == NEGATIVE_INFINITY); 483 } 484 485 /** 486 * The value of the Float. 487 * 488 * @serial 489 */ 490 private final float value; 491 492 /** 493 * Constructs a newly allocated {@code Float} object that 494 * represents the primitive {@code float} argument. 495 * 496 * @param value the value to be represented by the {@code Float}. 497 */ 498 public Float(float value) { 499 this.value = value; 500 } 501 502 /** 503 * Constructs a newly allocated {@code Float} object that 504 * represents the argument converted to type {@code float}. 505 * 506 * @param value the value to be represented by the {@code Float}. 507 */ 508 public Float(double value) { 509 this.value = (float)value; 510 } 511 512 /** 513 * Constructs a newly allocated {@code Float} object that 514 * represents the floating-point value of type {@code float} 515 * represented by the string. The string is converted to a 516 * {@code float} value as if by the {@code valueOf} method. 517 * 518 * @param s a string to be converted to a {@code Float}. 519 * @throws NumberFormatException if the string does not contain a 520 * parsable number. 521 * @see java.lang.Float#valueOf(java.lang.String) 522 */ 523 public Float(String s) throws NumberFormatException { 524 // REMIND: this is inefficient 525 this(valueOf(s).floatValue()); 526 } 527 528 /** 529 * Returns {@code true} if this {@code Float} value is a 530 * Not-a-Number (NaN), {@code false} otherwise. 531 * 532 * @return {@code true} if the value represented by this object is 533 * NaN; {@code false} otherwise. 534 */ 535 public boolean isNaN() { 536 return isNaN(value); 537 } 538 539 /** 540 * Returns {@code true} if this {@code Float} value is 541 * infinitely large in magnitude, {@code false} otherwise. 542 * 543 * @return {@code true} if the value represented by this object is 544 * positive infinity or negative infinity; 545 * {@code false} otherwise. 546 */ 547 public boolean isInfinite() { 548 return isInfinite(value); 549 } 550 551 /** 552 * Returns a string representation of this {@code Float} object. 553 * The primitive {@code float} value represented by this object 554 * is converted to a {@code String} exactly as if by the method 555 * {@code toString} of one argument. 556 * 557 * @return a {@code String} representation of this object. 558 * @see java.lang.Float#toString(float) 559 */ 560 public String toString() { 561 return Float.toString(value); 562 } 563 564 /** 565 * Returns the value of this {@code Float} as a {@code byte} after 566 * a narrowing primitive conversion. 567 * 568 * @return the {@code float} value represented by this object 569 * converted to type {@code byte} 570 * @jls 5.1.3 Narrowing Primitive Conversions 571 */ 572 public byte byteValue() { 573 return (byte)value; 574 } 575 576 /** 577 * Returns the value of this {@code Float} as a {@code short} 578 * after a narrowing primitive conversion. 579 * 580 * @return the {@code float} value represented by this object 581 * converted to type {@code short} 582 * @jls 5.1.3 Narrowing Primitive Conversions 583 * @since JDK1.1 584 */ 585 public short shortValue() { 586 return (short)value; 587 } 588 589 /** 590 * Returns the value of this {@code Float} as an {@code int} after 591 * a narrowing primitive conversion. 592 * 593 * @return the {@code float} value represented by this object 594 * converted to type {@code int} 595 * @jls 5.1.3 Narrowing Primitive Conversions 596 */ 597 public int intValue() { 598 return (int)value; 599 } 600 601 /** 602 * Returns value of this {@code Float} as a {@code long} after a 603 * narrowing primitive conversion. 604 * 605 * @return the {@code float} value represented by this object 606 * converted to type {@code long} 607 * @jls 5.1.3 Narrowing Primitive Conversions 608 */ 609 public long longValue() { 610 return (long)value; 611 } 612 613 /** 614 * Returns the {@code float} value of this {@code Float} object. 615 * 616 * @return the {@code float} value represented by this object 617 */ 618 public float floatValue() { 619 return value; 620 } 621 622 /** 623 * Returns the value of this {@code Float} as a {@code double} 624 * after a widening primitive conversion. 625 * 626 * @return the {@code float} value represented by this 627 * object converted to type {@code double} 628 * @jls 5.1.2 Widening Primitive Conversions 629 */ 630 public double doubleValue() { 631 return (double)value; 632 } 633 634 /** 635 * Returns a hash code for this {@code Float} object. The 636 * result is the integer bit representation, exactly as produced 637 * by the method {@link #floatToIntBits(float)}, of the primitive 638 * {@code float} value represented by this {@code Float} 639 * object. 640 * 641 * @return a hash code value for this object. 642 */ 643 public int hashCode() { 644 return floatToIntBits(value); 645 } 646 647 /** 648 * Returns a hash code for a {@code float} value; compatible with 649 * {@code Float.hashCode()}. 650 * 651 * @since 1.8 652 * 653 * @return a hash code value for a {@code float} value. 654 */ 655 public static int hashCode(float value) { 656 return floatToIntBits(value); 657 } 658 659 /** 660 661 * Compares this object against the specified object. The result 662 * is {@code true} if and only if the argument is not 663 * {@code null} and is a {@code Float} object that 664 * represents a {@code float} with the same value as the 665 * {@code float} represented by this object. For this 666 * purpose, two {@code float} values are considered to be the 667 * same if and only if the method {@link #floatToIntBits(float)} 668 * returns the identical {@code int} value when applied to 669 * each. 670 * 671 * <p>Note that in most cases, for two instances of class 672 * {@code Float}, {@code f1} and {@code f2}, the value 673 * of {@code f1.equals(f2)} is {@code true} if and only if 674 * 675 * <blockquote><pre> 676 * f1.floatValue() == f2.floatValue() 677 * </pre></blockquote> 678 * 679 * <p>also has the value {@code true}. However, there are two exceptions: 680 * <ul> 681 * <li>If {@code f1} and {@code f2} both represent 682 * {@code Float.NaN}, then the {@code equals} method returns 683 * {@code true}, even though {@code Float.NaN==Float.NaN} 684 * has the value {@code false}. 685 * <li>If {@code f1} represents {@code +0.0f} while 686 * {@code f2} represents {@code -0.0f}, or vice 687 * versa, the {@code equal} test has the value 688 * {@code false}, even though {@code 0.0f==-0.0f} 689 * has the value {@code true}. 690 * </ul> 691 * 692 * This definition allows hash tables to operate properly. 693 * 694 * @param obj the object to be compared 695 * @return {@code true} if the objects are the same; 696 * {@code false} otherwise. 697 * @see java.lang.Float#floatToIntBits(float) 698 */ 699 public boolean equals(Object obj) { 700 return (obj instanceof Float) 701 && (floatToIntBits(((Float)obj).value) == floatToIntBits(value)); 702 } 703 704 /** 705 * Returns a representation of the specified floating-point value 706 * according to the IEEE 754 floating-point "single format" bit 707 * layout. 708 * 709 * <p>Bit 31 (the bit that is selected by the mask 710 * {@code 0x80000000}) represents the sign of the floating-point 711 * number. 712 * Bits 30-23 (the bits that are selected by the mask 713 * {@code 0x7f800000}) represent the exponent. 714 * Bits 22-0 (the bits that are selected by the mask 715 * {@code 0x007fffff}) represent the significand (sometimes called 716 * the mantissa) of the floating-point number. 717 * 718 * <p>If the argument is positive infinity, the result is 719 * {@code 0x7f800000}. 720 * 721 * <p>If the argument is negative infinity, the result is 722 * {@code 0xff800000}. 723 * 724 * <p>If the argument is NaN, the result is {@code 0x7fc00000}. 725 * 726 * <p>In all cases, the result is an integer that, when given to the 727 * {@link #intBitsToFloat(int)} method, will produce a floating-point 728 * value the same as the argument to {@code floatToIntBits} 729 * (except all NaN values are collapsed to a single 730 * "canonical" NaN value). 731 * 732 * @param value a floating-point number. 733 * @return the bits that represent the floating-point number. 734 */ 735 public static int floatToIntBits(float value) { 736 int result = floatToRawIntBits(value); 737 // Check for NaN based on values of bit fields, maximum 738 // exponent and nonzero significand. 739 if ( ((result & FloatConsts.EXP_BIT_MASK) == 740 FloatConsts.EXP_BIT_MASK) && 741 (result & FloatConsts.SIGNIF_BIT_MASK) != 0) 742 result = 0x7fc00000; 743 return result; 744 } 745 746 /** 747 * Returns a representation of the specified floating-point value 748 * according to the IEEE 754 floating-point "single format" bit 749 * layout, preserving Not-a-Number (NaN) values. 750 * 751 * <p>Bit 31 (the bit that is selected by the mask 752 * {@code 0x80000000}) represents the sign of the floating-point 753 * number. 754 * Bits 30-23 (the bits that are selected by the mask 755 * {@code 0x7f800000}) represent the exponent. 756 * Bits 22-0 (the bits that are selected by the mask 757 * {@code 0x007fffff}) represent the significand (sometimes called 758 * the mantissa) of the floating-point number. 759 * 760 * <p>If the argument is positive infinity, the result is 761 * {@code 0x7f800000}. 762 * 763 * <p>If the argument is negative infinity, the result is 764 * {@code 0xff800000}. 765 * 766 * <p>If the argument is NaN, the result is the integer representing 767 * the actual NaN value. Unlike the {@code floatToIntBits} 768 * method, {@code floatToRawIntBits} does not collapse all the 769 * bit patterns encoding a NaN to a single "canonical" 770 * NaN value. 771 * 772 * <p>In all cases, the result is an integer that, when given to the 773 * {@link #intBitsToFloat(int)} method, will produce a 774 * floating-point value the same as the argument to 775 * {@code floatToRawIntBits}. 776 * 777 * @param value a floating-point number. 778 * @return the bits that represent the floating-point number. 779 * @since 1.3 780 */ 781 public static native int floatToRawIntBits(float value); 782 783 /** 784 * Returns the {@code float} value corresponding to a given 785 * bit representation. 786 * The argument is considered to be a representation of a 787 * floating-point value according to the IEEE 754 floating-point 788 * "single format" bit layout. 789 * 790 * <p>If the argument is {@code 0x7f800000}, the result is positive 791 * infinity. 792 * 793 * <p>If the argument is {@code 0xff800000}, the result is negative 794 * infinity. 795 * 796 * <p>If the argument is any value in the range 797 * {@code 0x7f800001} through {@code 0x7fffffff} or in 798 * the range {@code 0xff800001} through 799 * {@code 0xffffffff}, the result is a NaN. No IEEE 754 800 * floating-point operation provided by Java can distinguish 801 * between two NaN values of the same type with different bit 802 * patterns. Distinct values of NaN are only distinguishable by 803 * use of the {@code Float.floatToRawIntBits} method. 804 * 805 * <p>In all other cases, let <i>s</i>, <i>e</i>, and <i>m</i> be three 806 * values that can be computed from the argument: 807 * 808 * <blockquote><pre> 809 * int s = ((bits >> 31) == 0) ? 1 : -1; 810 * int e = ((bits >> 23) & 0xff); 811 * int m = (e == 0) ? 812 * (bits & 0x7fffff) << 1 : 813 * (bits & 0x7fffff) | 0x800000; 814 * </pre></blockquote> 815 * 816 * Then the floating-point result equals the value of the mathematical 817 * expression <i>s</i>·<i>m</i>·2<sup><i>e</i>-150</sup>. 818 * 819 * <p>Note that this method may not be able to return a 820 * {@code float} NaN with exactly same bit pattern as the 821 * {@code int} argument. IEEE 754 distinguishes between two 822 * kinds of NaNs, quiet NaNs and <i>signaling NaNs</i>. The 823 * differences between the two kinds of NaN are generally not 824 * visible in Java. Arithmetic operations on signaling NaNs turn 825 * them into quiet NaNs with a different, but often similar, bit 826 * pattern. However, on some processors merely copying a 827 * signaling NaN also performs that conversion. In particular, 828 * copying a signaling NaN to return it to the calling method may 829 * perform this conversion. So {@code intBitsToFloat} may 830 * not be able to return a {@code float} with a signaling NaN 831 * bit pattern. Consequently, for some {@code int} values, 832 * {@code floatToRawIntBits(intBitsToFloat(start))} may 833 * <i>not</i> equal {@code start}. Moreover, which 834 * particular bit patterns represent signaling NaNs is platform 835 * dependent; although all NaN bit patterns, quiet or signaling, 836 * must be in the NaN range identified above. 837 * 838 * @param bits an integer. 839 * @return the {@code float} floating-point value with the same bit 840 * pattern. 841 */ 842 public static native float intBitsToFloat(int bits); 843 844 /** 845 * Compares two {@code Float} objects numerically. There are 846 * two ways in which comparisons performed by this method differ 847 * from those performed by the Java language numerical comparison 848 * operators ({@code <, <=, ==, >=, >}) when 849 * applied to primitive {@code float} values: 850 * 851 * <ul><li> 852 * {@code Float.NaN} is considered by this method to 853 * be equal to itself and greater than all other 854 * {@code float} values 855 * (including {@code Float.POSITIVE_INFINITY}). 856 * <li> 857 * {@code 0.0f} is considered by this method to be greater 858 * than {@code -0.0f}. 859 * </ul> 860 * 861 * This ensures that the <i>natural ordering</i> of {@code Float} 862 * objects imposed by this method is <i>consistent with equals</i>. 863 * 864 * @param anotherFloat the {@code Float} to be compared. 865 * @return the value {@code 0} if {@code anotherFloat} is 866 * numerically equal to this {@code Float}; a value 867 * less than {@code 0} if this {@code Float} 868 * is numerically less than {@code anotherFloat}; 869 * and a value greater than {@code 0} if this 870 * {@code Float} is numerically greater than 871 * {@code anotherFloat}. 872 * 873 * @since 1.2 874 * @see Comparable#compareTo(Object) 875 */ 876 public int compareTo(Float anotherFloat) { 877 return Float.compare(value, anotherFloat.value); 878 } 879 880 /** 881 * Compares the two specified {@code float} values. The sign 882 * of the integer value returned is the same as that of the 883 * integer that would be returned by the call: 884 * <pre> 885 * new Float(f1).compareTo(new Float(f2)) 886 * </pre> 887 * 888 * @param f1 the first {@code float} to compare. 889 * @param f2 the second {@code float} to compare. 890 * @return the value {@code 0} if {@code f1} is 891 * numerically equal to {@code f2}; a value less than 892 * {@code 0} if {@code f1} is numerically less than 893 * {@code f2}; and a value greater than {@code 0} 894 * if {@code f1} is numerically greater than 895 * {@code f2}. 896 * @since 1.4 897 */ 898 public static int compare(float f1, float f2) { 899 if (f1 < f2) 900 return -1; // Neither val is NaN, thisVal is smaller 901 if (f1 > f2) 902 return 1; // Neither val is NaN, thisVal is larger 903 904 // Cannot use floatToRawIntBits because of possibility of NaNs. 905 int thisBits = Float.floatToIntBits(f1); 906 int anotherBits = Float.floatToIntBits(f2); 907 908 return (thisBits == anotherBits ? 0 : // Values are equal 909 (thisBits < anotherBits ? -1 : // (-0.0, 0.0) or (!NaN, NaN) 910 1)); // (0.0, -0.0) or (NaN, !NaN) 911 } 912 913 /** use serialVersionUID from JDK 1.0.2 for interoperability */ 914 private static final long serialVersionUID = -2671257302660747028L; 915 }