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 27 package java.lang; 28 29 import sun.misc.FloatingDecimal; 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 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 @SuppressWarnings("unchecked") 138 public static final Class<Float> TYPE = (Class<Float>) float[].class.getComponentType(); 139 140 /** 141 * Returns a string representation of the {@code float} 142 * argument. All characters mentioned below are ASCII characters. 143 * <ul> 144 * <li>If the argument is NaN, the result is the string 145 * "{@code NaN}". 146 * <li>Otherwise, the result is a string that represents the sign and 147 * magnitude (absolute value) of the argument. If the sign is 148 * negative, the first character of the result is 149 * '{@code -}' ({@code '\u005Cu002D'}); if the sign is 150 * positive, no sign character appears in the result. As for 151 * the magnitude <i>m</i>: 152 * <ul> 153 * <li>If <i>m</i> is infinity, it is represented by the characters 154 * {@code "Infinity"}; thus, positive infinity produces 155 * the result {@code "Infinity"} and negative infinity 156 * produces the result {@code "-Infinity"}. 157 * <li>If <i>m</i> is zero, it is represented by the characters 158 * {@code "0.0"}; thus, negative zero produces the result 159 * {@code "-0.0"} and positive zero produces the result 160 * {@code "0.0"}. 161 * <li> If <i>m</i> is greater than or equal to 10<sup>-3</sup> but 162 * less than 10<sup>7</sup>, then it is represented as the 163 * integer part of <i>m</i>, in decimal form with no leading 164 * zeroes, followed by '{@code .}' 165 * ({@code '\u005Cu002E'}), followed by one or more 166 * decimal digits representing the fractional part of 167 * <i>m</i>. 168 * <li> If <i>m</i> is less than 10<sup>-3</sup> or greater than or 169 * equal to 10<sup>7</sup>, then it is represented in 170 * so-called "computerized scientific notation." Let <i>n</i> 171 * be the unique integer such that 10<sup><i>n</i> </sup>≤ 172 * <i>m</i> {@literal <} 10<sup><i>n</i>+1</sup>; then let <i>a</i> 173 * be the mathematically exact quotient of <i>m</i> and 174 * 10<sup><i>n</i></sup> so that 1 ≤ <i>a</i> {@literal <} 10. 175 * The magnitude is then represented as the integer part of 176 * <i>a</i>, as a single decimal digit, followed by 177 * '{@code .}' ({@code '\u005Cu002E'}), followed by 178 * decimal digits representing the fractional part of 179 * <i>a</i>, followed by the letter '{@code E}' 180 * ({@code '\u005Cu0045'}), followed by a representation 181 * of <i>n</i> as a decimal integer, as produced by the 182 * method {@link java.lang.Integer#toString(int)}. 183 * 184 * </ul> 185 * </ul> 186 * How many digits must be printed for the fractional part of 187 * <i>m</i> or <i>a</i>? There must be at least one digit 188 * to represent the fractional part, and beyond that as many, but 189 * only as many, more digits as are needed to uniquely distinguish 190 * the argument value from adjacent values of type 191 * {@code float}. That is, suppose that <i>x</i> is the 192 * exact mathematical value represented by the decimal 193 * representation produced by this method for a finite nonzero 194 * argument <i>f</i>. Then <i>f</i> must be the {@code float} 195 * value nearest to <i>x</i>; or, if two {@code float} values are 196 * equally close to <i>x</i>, then <i>f</i> must be one of 197 * them and the least significant bit of the significand of 198 * <i>f</i> must be {@code 0}. 199 * 200 * <p>To create localized string representations of a floating-point 201 * value, use subclasses of {@link java.text.NumberFormat}. 202 * 203 * @param f the float to be converted. 204 * @return a string representation of the argument. 205 */ toString(float f)206 public static String toString(float f) { 207 return FloatingDecimal.toJavaFormatString(f); 208 } 209 210 /** 211 * Returns a hexadecimal string representation of the 212 * {@code float} argument. All characters mentioned below are 213 * ASCII characters. 214 * 215 * <ul> 216 * <li>If the argument is NaN, the result is the string 217 * "{@code NaN}". 218 * <li>Otherwise, the result is a string that represents the sign and 219 * magnitude (absolute value) of the argument. If the sign is negative, 220 * the first character of the result is '{@code -}' 221 * ({@code '\u005Cu002D'}); if the sign is positive, no sign character 222 * appears in the result. As for the magnitude <i>m</i>: 223 * 224 * <ul> 225 * <li>If <i>m</i> is infinity, it is represented by the string 226 * {@code "Infinity"}; thus, positive infinity produces the 227 * result {@code "Infinity"} and negative infinity produces 228 * the result {@code "-Infinity"}. 229 * 230 * <li>If <i>m</i> is zero, it is represented by the string 231 * {@code "0x0.0p0"}; thus, negative zero produces the result 232 * {@code "-0x0.0p0"} and positive zero produces the result 233 * {@code "0x0.0p0"}. 234 * 235 * <li>If <i>m</i> is a {@code float} value with a 236 * normalized representation, substrings are used to represent the 237 * significand and exponent fields. The significand is 238 * represented by the characters {@code "0x1."} 239 * followed by a lowercase hexadecimal representation of the rest 240 * of the significand as a fraction. Trailing zeros in the 241 * hexadecimal representation are removed unless all the digits 242 * are zero, in which case a single zero is used. Next, the 243 * exponent is represented by {@code "p"} followed 244 * by a decimal string of the unbiased exponent as if produced by 245 * a call to {@link Integer#toString(int) Integer.toString} on the 246 * exponent value. 247 * 248 * <li>If <i>m</i> is a {@code float} value with a subnormal 249 * representation, the significand is represented by the 250 * characters {@code "0x0."} followed by a 251 * hexadecimal representation of the rest of the significand as a 252 * fraction. Trailing zeros in the hexadecimal representation are 253 * removed. Next, the exponent is represented by 254 * {@code "p-126"}. Note that there must be at 255 * least one nonzero digit in a subnormal significand. 256 * 257 * </ul> 258 * 259 * </ul> 260 * 261 * <table border> 262 * <caption>Examples</caption> 263 * <tr><th>Floating-point Value</th><th>Hexadecimal String</th> 264 * <tr><td>{@code 1.0}</td> <td>{@code 0x1.0p0}</td> 265 * <tr><td>{@code -1.0}</td> <td>{@code -0x1.0p0}</td> 266 * <tr><td>{@code 2.0}</td> <td>{@code 0x1.0p1}</td> 267 * <tr><td>{@code 3.0}</td> <td>{@code 0x1.8p1}</td> 268 * <tr><td>{@code 0.5}</td> <td>{@code 0x1.0p-1}</td> 269 * <tr><td>{@code 0.25}</td> <td>{@code 0x1.0p-2}</td> 270 * <tr><td>{@code Float.MAX_VALUE}</td> 271 * <td>{@code 0x1.fffffep127}</td> 272 * <tr><td>{@code Minimum Normal Value}</td> 273 * <td>{@code 0x1.0p-126}</td> 274 * <tr><td>{@code Maximum Subnormal Value}</td> 275 * <td>{@code 0x0.fffffep-126}</td> 276 * <tr><td>{@code Float.MIN_VALUE}</td> 277 * <td>{@code 0x0.000002p-126}</td> 278 * </table> 279 * @param f the {@code float} to be converted. 280 * @return a hex string representation of the argument. 281 * @since 1.5 282 * @author Joseph D. Darcy 283 */ toHexString(float f)284 public static String toHexString(float f) { 285 if (Math.abs(f) < FloatConsts.MIN_NORMAL 286 && f != 0.0f ) {// float subnormal 287 // Adjust exponent to create subnormal double, then 288 // replace subnormal double exponent with subnormal float 289 // exponent 290 String s = Double.toHexString(Math.scalb((double)f, 291 /* -1022+126 */ 292 DoubleConsts.MIN_EXPONENT- 293 FloatConsts.MIN_EXPONENT)); 294 return s.replaceFirst("p-1022$", "p-126"); 295 } 296 else // double string will be the same as float string 297 return Double.toHexString(f); 298 } 299 300 /** 301 * Returns a {@code Float} object holding the 302 * {@code float} value represented by the argument string 303 * {@code s}. 304 * 305 * <p>If {@code s} is {@code null}, then a 306 * {@code NullPointerException} is thrown. 307 * 308 * <p>Leading and trailing whitespace characters in {@code s} 309 * are ignored. Whitespace is removed as if by the {@link 310 * String#trim} method; that is, both ASCII space and control 311 * characters are removed. The rest of {@code s} should 312 * constitute a <i>FloatValue</i> as described by the lexical 313 * syntax rules: 314 * 315 * <blockquote> 316 * <dl> 317 * <dt><i>FloatValue:</i> 318 * <dd><i>Sign<sub>opt</sub></i> {@code NaN} 319 * <dd><i>Sign<sub>opt</sub></i> {@code Infinity} 320 * <dd><i>Sign<sub>opt</sub> FloatingPointLiteral</i> 321 * <dd><i>Sign<sub>opt</sub> HexFloatingPointLiteral</i> 322 * <dd><i>SignedInteger</i> 323 * </dl> 324 * 325 * <dl> 326 * <dt><i>HexFloatingPointLiteral</i>: 327 * <dd> <i>HexSignificand BinaryExponent FloatTypeSuffix<sub>opt</sub></i> 328 * </dl> 329 * 330 * <dl> 331 * <dt><i>HexSignificand:</i> 332 * <dd><i>HexNumeral</i> 333 * <dd><i>HexNumeral</i> {@code .} 334 * <dd>{@code 0x} <i>HexDigits<sub>opt</sub> 335 * </i>{@code .}<i> HexDigits</i> 336 * <dd>{@code 0X}<i> HexDigits<sub>opt</sub> 337 * </i>{@code .} <i>HexDigits</i> 338 * </dl> 339 * 340 * <dl> 341 * <dt><i>BinaryExponent:</i> 342 * <dd><i>BinaryExponentIndicator SignedInteger</i> 343 * </dl> 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 357 * <cite>The Java™ Language Specification</cite>, 358 * except that underscores are not accepted between digits. 359 * If {@code s} does not have the form of 360 * a <i>FloatValue</i>, then a {@code NumberFormatException} 361 * is thrown. Otherwise, {@code s} is regarded as 362 * representing an exact decimal value in the usual 363 * "computerized scientific notation" or as an exact 364 * hexadecimal value; this exact numerical value is then 365 * conceptually converted to an "infinitely precise" 366 * binary value that is then rounded to type {@code float} 367 * by the usual round-to-nearest rule of IEEE 754 floating-point 368 * arithmetic, which includes preserving the sign of a zero 369 * value. 370 * 371 * Note that the round-to-nearest rule also implies overflow and 372 * underflow behaviour; if the exact value of {@code s} is large 373 * enough in magnitude (greater than or equal to ({@link 374 * #MAX_VALUE} + {@link Math#ulp(float) ulp(MAX_VALUE)}/2), 375 * rounding to {@code float} will result in an infinity and if the 376 * exact value of {@code s} is small enough in magnitude (less 377 * than or equal to {@link #MIN_VALUE}/2), rounding to float will 378 * result in a zero. 379 * 380 * Finally, after rounding a {@code Float} object representing 381 * this {@code float} value is returned. 382 * 383 * <p>To interpret localized string representations of a 384 * floating-point value, use subclasses of {@link 385 * java.text.NumberFormat}. 386 * 387 * <p>Note that trailing format specifiers, specifiers that 388 * determine the type of a floating-point literal 389 * ({@code 1.0f} is a {@code float} value; 390 * {@code 1.0d} is a {@code double} value), do 391 * <em>not</em> influence the results of this method. In other 392 * words, the numerical value of the input string is converted 393 * directly to the target floating-point type. In general, the 394 * two-step sequence of conversions, string to {@code double} 395 * followed by {@code double} to {@code float}, is 396 * <em>not</em> equivalent to converting a string directly to 397 * {@code float}. For example, if first converted to an 398 * intermediate {@code double} and then to 399 * {@code float}, the string<br> 400 * {@code "1.00000017881393421514957253748434595763683319091796875001d"}<br> 401 * results in the {@code float} value 402 * {@code 1.0000002f}; if the string is converted directly to 403 * {@code float}, <code>1.000000<b>1</b>f</code> results. 404 * 405 * <p>To avoid calling this method on an invalid string and having 406 * a {@code NumberFormatException} be thrown, the documentation 407 * for {@link Double#valueOf Double.valueOf} lists a regular 408 * expression which can be used to screen the input. 409 * 410 * @param s the string to be parsed. 411 * @return a {@code Float} object holding the value 412 * represented by the {@code String} argument. 413 * @throws NumberFormatException if the string does not contain a 414 * parsable number. 415 */ valueOf(String s)416 public static Float valueOf(String s) throws NumberFormatException { 417 return new Float(parseFloat(s)); 418 } 419 420 /** 421 * Returns a {@code Float} instance representing the specified 422 * {@code float} value. 423 * If a new {@code Float} instance is not required, this method 424 * should generally be used in preference to the constructor 425 * {@link #Float(float)}, as this method is likely to yield 426 * significantly better space and time performance by caching 427 * frequently requested values. 428 * 429 * @param f a float value. 430 * @return a {@code Float} instance representing {@code f}. 431 * @since 1.5 432 */ valueOf(float f)433 public static Float valueOf(float f) { 434 return new Float(f); 435 } 436 437 /** 438 * Returns a new {@code float} initialized to the value 439 * represented by the specified {@code String}, as performed 440 * by the {@code valueOf} method of class {@code Float}. 441 * 442 * @param s the string to be parsed. 443 * @return the {@code float} value represented by the string 444 * argument. 445 * @throws NullPointerException if the string is null 446 * @throws NumberFormatException if the string does not contain a 447 * parsable {@code float}. 448 * @see java.lang.Float#valueOf(String) 449 * @since 1.2 450 */ parseFloat(String s)451 public static float parseFloat(String s) throws NumberFormatException { 452 return FloatingDecimal.parseFloat(s); 453 } 454 455 /** 456 * Returns {@code true} if the specified number is a 457 * Not-a-Number (NaN) value, {@code false} otherwise. 458 * 459 * @param v the value to be tested. 460 * @return {@code true} if the argument is NaN; 461 * {@code false} otherwise. 462 */ isNaN(float v)463 public static boolean isNaN(float v) { 464 return (v != v); 465 } 466 467 /** 468 * Returns {@code true} if the specified number is infinitely 469 * large in magnitude, {@code false} otherwise. 470 * 471 * @param v the value to be tested. 472 * @return {@code true} if the argument is positive infinity or 473 * negative infinity; {@code false} otherwise. 474 */ isInfinite(float v)475 public static boolean isInfinite(float v) { 476 return (v == POSITIVE_INFINITY) || (v == NEGATIVE_INFINITY); 477 } 478 479 480 /** 481 * Returns {@code true} if the argument is a finite floating-point 482 * value; returns {@code false} otherwise (for NaN and infinity 483 * arguments). 484 * 485 * @param f the {@code float} value to be tested 486 * @return {@code true} if the argument is a finite 487 * floating-point value, {@code false} otherwise. 488 * @since 1.8 489 */ isFinite(float f)490 public static boolean isFinite(float f) { 491 return Math.abs(f) <= FloatConsts.MAX_VALUE; 492 } 493 494 /** 495 * The value of the Float. 496 * 497 * @serial 498 */ 499 private final float value; 500 501 /** 502 * Constructs a newly allocated {@code Float} object that 503 * represents the primitive {@code float} argument. 504 * 505 * @param value the value to be represented by the {@code Float}. 506 */ Float(float value)507 public Float(float value) { 508 this.value = value; 509 } 510 511 /** 512 * Constructs a newly allocated {@code Float} object that 513 * represents the argument converted to type {@code float}. 514 * 515 * @param value the value to be represented by the {@code Float}. 516 */ Float(double value)517 public Float(double value) { 518 this.value = (float)value; 519 } 520 521 /** 522 * Constructs a newly allocated {@code Float} object that 523 * represents the floating-point value of type {@code float} 524 * represented by the string. The string is converted to a 525 * {@code float} value as if by the {@code valueOf} method. 526 * 527 * @param s a string to be converted to a {@code Float}. 528 * @throws NumberFormatException if the string does not contain a 529 * parsable number. 530 * @see java.lang.Float#valueOf(java.lang.String) 531 */ Float(String s)532 public Float(String s) throws NumberFormatException { 533 value = parseFloat(s); 534 } 535 536 /** 537 * Returns {@code true} if this {@code Float} value is a 538 * Not-a-Number (NaN), {@code false} otherwise. 539 * 540 * @return {@code true} if the value represented by this object is 541 * NaN; {@code false} otherwise. 542 */ isNaN()543 public boolean isNaN() { 544 return isNaN(value); 545 } 546 547 /** 548 * Returns {@code true} if this {@code Float} value is 549 * infinitely large in magnitude, {@code false} otherwise. 550 * 551 * @return {@code true} if the value represented by this object is 552 * positive infinity or negative infinity; 553 * {@code false} otherwise. 554 */ isInfinite()555 public boolean isInfinite() { 556 return isInfinite(value); 557 } 558 559 /** 560 * Returns a string representation of this {@code Float} object. 561 * The primitive {@code float} value represented by this object 562 * is converted to a {@code String} exactly as if by the method 563 * {@code toString} of one argument. 564 * 565 * @return a {@code String} representation of this object. 566 * @see java.lang.Float#toString(float) 567 */ toString()568 public String toString() { 569 return Float.toString(value); 570 } 571 572 /** 573 * Returns the value of this {@code Float} as a {@code byte} after 574 * a narrowing primitive conversion. 575 * 576 * @return the {@code float} value represented by this object 577 * converted to type {@code byte} 578 * @jls 5.1.3 Narrowing Primitive Conversions 579 */ byteValue()580 public byte byteValue() { 581 return (byte)value; 582 } 583 584 /** 585 * Returns the value of this {@code Float} as a {@code short} 586 * after a narrowing primitive conversion. 587 * 588 * @return the {@code float} value represented by this object 589 * converted to type {@code short} 590 * @jls 5.1.3 Narrowing Primitive Conversions 591 * @since JDK1.1 592 */ shortValue()593 public short shortValue() { 594 return (short)value; 595 } 596 597 /** 598 * Returns the value of this {@code Float} as an {@code int} after 599 * a narrowing primitive conversion. 600 * 601 * @return the {@code float} value represented by this object 602 * converted to type {@code int} 603 * @jls 5.1.3 Narrowing Primitive Conversions 604 */ intValue()605 public int intValue() { 606 return (int)value; 607 } 608 609 /** 610 * Returns value of this {@code Float} as a {@code long} after a 611 * narrowing primitive conversion. 612 * 613 * @return the {@code float} value represented by this object 614 * converted to type {@code long} 615 * @jls 5.1.3 Narrowing Primitive Conversions 616 */ longValue()617 public long longValue() { 618 return (long)value; 619 } 620 621 /** 622 * Returns the {@code float} value of this {@code Float} object. 623 * 624 * @return the {@code float} value represented by this object 625 */ floatValue()626 public float floatValue() { 627 return value; 628 } 629 630 /** 631 * Returns the value of this {@code Float} as a {@code double} 632 * after a widening primitive conversion. 633 * 634 * @return the {@code float} value represented by this 635 * object converted to type {@code double} 636 * @jls 5.1.2 Widening Primitive Conversions 637 */ doubleValue()638 public double doubleValue() { 639 return (double)value; 640 } 641 642 /** 643 * Returns a hash code for this {@code Float} object. The 644 * result is the integer bit representation, exactly as produced 645 * by the method {@link #floatToIntBits(float)}, of the primitive 646 * {@code float} value represented by this {@code Float} 647 * object. 648 * 649 * @return a hash code value for this object. 650 */ 651 @Override hashCode()652 public int hashCode() { 653 return Float.hashCode(value); 654 } 655 656 /** 657 * Returns a hash code for a {@code float} value; compatible with 658 * {@code Float.hashCode()}. 659 * 660 * @param value the value to hash 661 * @return a hash code value for a {@code float} value. 662 * @since 1.8 663 */ hashCode(float value)664 public static int hashCode(float value) { 665 return floatToIntBits(value); 666 } 667 668 /** 669 670 * Compares this object against the specified object. The result 671 * is {@code true} if and only if the argument is not 672 * {@code null} and is a {@code Float} object that 673 * represents a {@code float} with the same value as the 674 * {@code float} represented by this object. For this 675 * purpose, two {@code float} values are considered to be the 676 * same if and only if the method {@link #floatToIntBits(float)} 677 * returns the identical {@code int} value when applied to 678 * each. 679 * 680 * <p>Note that in most cases, for two instances of class 681 * {@code Float}, {@code f1} and {@code f2}, the value 682 * of {@code f1.equals(f2)} is {@code true} if and only if 683 * 684 * <blockquote><pre> 685 * f1.floatValue() == f2.floatValue() 686 * </pre></blockquote> 687 * 688 * <p>also has the value {@code true}. However, there are two exceptions: 689 * <ul> 690 * <li>If {@code f1} and {@code f2} both represent 691 * {@code Float.NaN}, then the {@code equals} method returns 692 * {@code true}, even though {@code Float.NaN==Float.NaN} 693 * has the value {@code false}. 694 * <li>If {@code f1} represents {@code +0.0f} while 695 * {@code f2} represents {@code -0.0f}, or vice 696 * versa, the {@code equal} test has the value 697 * {@code false}, even though {@code 0.0f==-0.0f} 698 * has the value {@code true}. 699 * </ul> 700 * 701 * This definition allows hash tables to operate properly. 702 * 703 * @param obj the object to be compared 704 * @return {@code true} if the objects are the same; 705 * {@code false} otherwise. 706 * @see java.lang.Float#floatToIntBits(float) 707 */ equals(Object obj)708 public boolean equals(Object obj) { 709 return (obj instanceof Float) 710 && (floatToIntBits(((Float)obj).value) == floatToIntBits(value)); 711 } 712 713 /** 714 * Returns a representation of the specified floating-point value 715 * according to the IEEE 754 floating-point "single format" bit 716 * layout. 717 * 718 * <p>Bit 31 (the bit that is selected by the mask 719 * {@code 0x80000000}) represents the sign of the floating-point 720 * number. 721 * Bits 30-23 (the bits that are selected by the mask 722 * {@code 0x7f800000}) represent the exponent. 723 * Bits 22-0 (the bits that are selected by the mask 724 * {@code 0x007fffff}) represent the significand (sometimes called 725 * the mantissa) of the floating-point number. 726 * 727 * <p>If the argument is positive infinity, the result is 728 * {@code 0x7f800000}. 729 * 730 * <p>If the argument is negative infinity, the result is 731 * {@code 0xff800000}. 732 * 733 * <p>If the argument is NaN, the result is {@code 0x7fc00000}. 734 * 735 * <p>In all cases, the result is an integer that, when given to the 736 * {@link #intBitsToFloat(int)} method, will produce a floating-point 737 * value the same as the argument to {@code floatToIntBits} 738 * (except all NaN values are collapsed to a single 739 * "canonical" NaN value). 740 * 741 * @param value a floating-point number. 742 * @return the bits that represent the floating-point number. 743 */ floatToIntBits(float value)744 public static int floatToIntBits(float value) { 745 int result = floatToRawIntBits(value); 746 // Check for NaN based on values of bit fields, maximum 747 // exponent and nonzero significand. 748 if ( ((result & FloatConsts.EXP_BIT_MASK) == 749 FloatConsts.EXP_BIT_MASK) && 750 (result & FloatConsts.SIGNIF_BIT_MASK) != 0) 751 result = 0x7fc00000; 752 return result; 753 } 754 755 /** 756 * Returns a representation of the specified floating-point value 757 * according to the IEEE 754 floating-point "single format" bit 758 * layout, preserving Not-a-Number (NaN) values. 759 * 760 * <p>Bit 31 (the bit that is selected by the mask 761 * {@code 0x80000000}) represents the sign of the floating-point 762 * number. 763 * Bits 30-23 (the bits that are selected by the mask 764 * {@code 0x7f800000}) represent the exponent. 765 * Bits 22-0 (the bits that are selected by the mask 766 * {@code 0x007fffff}) represent the significand (sometimes called 767 * the mantissa) of the floating-point number. 768 * 769 * <p>If the argument is positive infinity, the result is 770 * {@code 0x7f800000}. 771 * 772 * <p>If the argument is negative infinity, the result is 773 * {@code 0xff800000}. 774 * 775 * <p>If the argument is NaN, the result is the integer representing 776 * the actual NaN value. Unlike the {@code floatToIntBits} 777 * method, {@code floatToRawIntBits} does not collapse all the 778 * bit patterns encoding a NaN to a single "canonical" 779 * NaN value. 780 * 781 * <p>In all cases, the result is an integer that, when given to the 782 * {@link #intBitsToFloat(int)} method, will produce a 783 * floating-point value the same as the argument to 784 * {@code floatToRawIntBits}. 785 * 786 * @param value a floating-point number. 787 * @return the bits that represent the floating-point number. 788 * @since 1.3 789 */ floatToRawIntBits(float value)790 public static native int floatToRawIntBits(float value); 791 792 /** 793 * Returns the {@code float} value corresponding to a given 794 * bit representation. 795 * The argument is considered to be a representation of a 796 * floating-point value according to the IEEE 754 floating-point 797 * "single format" bit layout. 798 * 799 * <p>If the argument is {@code 0x7f800000}, the result is positive 800 * infinity. 801 * 802 * <p>If the argument is {@code 0xff800000}, the result is negative 803 * infinity. 804 * 805 * <p>If the argument is any value in the range 806 * {@code 0x7f800001} through {@code 0x7fffffff} or in 807 * the range {@code 0xff800001} through 808 * {@code 0xffffffff}, the result is a NaN. No IEEE 754 809 * floating-point operation provided by Java can distinguish 810 * between two NaN values of the same type with different bit 811 * patterns. Distinct values of NaN are only distinguishable by 812 * use of the {@code Float.floatToRawIntBits} method. 813 * 814 * <p>In all other cases, let <i>s</i>, <i>e</i>, and <i>m</i> be three 815 * values that can be computed from the argument: 816 * 817 * <blockquote><pre>{@code 818 * int s = ((bits >> 31) == 0) ? 1 : -1; 819 * int e = ((bits >> 23) & 0xff); 820 * int m = (e == 0) ? 821 * (bits & 0x7fffff) << 1 : 822 * (bits & 0x7fffff) | 0x800000; 823 * }</pre></blockquote> 824 * 825 * Then the floating-point result equals the value of the mathematical 826 * expression <i>s</i>·<i>m</i>·2<sup><i>e</i>-150</sup>. 827 * 828 * <p>Note that this method may not be able to return a 829 * {@code float} NaN with exactly same bit pattern as the 830 * {@code int} argument. IEEE 754 distinguishes between two 831 * kinds of NaNs, quiet NaNs and <i>signaling NaNs</i>. The 832 * differences between the two kinds of NaN are generally not 833 * visible in Java. Arithmetic operations on signaling NaNs turn 834 * them into quiet NaNs with a different, but often similar, bit 835 * pattern. However, on some processors merely copying a 836 * signaling NaN also performs that conversion. In particular, 837 * copying a signaling NaN to return it to the calling method may 838 * perform this conversion. So {@code intBitsToFloat} may 839 * not be able to return a {@code float} with a signaling NaN 840 * bit pattern. Consequently, for some {@code int} values, 841 * {@code floatToRawIntBits(intBitsToFloat(start))} may 842 * <i>not</i> equal {@code start}. Moreover, which 843 * particular bit patterns represent signaling NaNs is platform 844 * dependent; although all NaN bit patterns, quiet or signaling, 845 * must be in the NaN range identified above. 846 * 847 * @param bits an integer. 848 * @return the {@code float} floating-point value with the same bit 849 * pattern. 850 */ intBitsToFloat(int bits)851 public static native float intBitsToFloat(int bits); 852 853 /** 854 * Compares two {@code Float} objects numerically. There are 855 * two ways in which comparisons performed by this method differ 856 * from those performed by the Java language numerical comparison 857 * operators ({@code <, <=, ==, >=, >}) when 858 * applied to primitive {@code float} values: 859 * 860 * <ul><li> 861 * {@code Float.NaN} is considered by this method to 862 * be equal to itself and greater than all other 863 * {@code float} values 864 * (including {@code Float.POSITIVE_INFINITY}). 865 * <li> 866 * {@code 0.0f} is considered by this method to be greater 867 * than {@code -0.0f}. 868 * </ul> 869 * 870 * This ensures that the <i>natural ordering</i> of {@code Float} 871 * objects imposed by this method is <i>consistent with equals</i>. 872 * 873 * @param anotherFloat the {@code Float} to be compared. 874 * @return the value {@code 0} if {@code anotherFloat} is 875 * numerically equal to this {@code Float}; a value 876 * less than {@code 0} if this {@code Float} 877 * is numerically less than {@code anotherFloat}; 878 * and a value greater than {@code 0} if this 879 * {@code Float} is numerically greater than 880 * {@code anotherFloat}. 881 * 882 * @since 1.2 883 * @see Comparable#compareTo(Object) 884 */ compareTo(Float anotherFloat)885 public int compareTo(Float anotherFloat) { 886 return Float.compare(value, anotherFloat.value); 887 } 888 889 /** 890 * Compares the two specified {@code float} values. The sign 891 * of the integer value returned is the same as that of the 892 * integer that would be returned by the call: 893 * <pre> 894 * new Float(f1).compareTo(new Float(f2)) 895 * </pre> 896 * 897 * @param f1 the first {@code float} to compare. 898 * @param f2 the second {@code float} to compare. 899 * @return the value {@code 0} if {@code f1} is 900 * numerically equal to {@code f2}; a value less than 901 * {@code 0} if {@code f1} is numerically less than 902 * {@code f2}; and a value greater than {@code 0} 903 * if {@code f1} is numerically greater than 904 * {@code f2}. 905 * @since 1.4 906 */ compare(float f1, float f2)907 public static int compare(float f1, float f2) { 908 if (f1 < f2) 909 return -1; // Neither val is NaN, thisVal is smaller 910 if (f1 > f2) 911 return 1; // Neither val is NaN, thisVal is larger 912 913 // Cannot use floatToRawIntBits because of possibility of NaNs. 914 int thisBits = Float.floatToIntBits(f1); 915 int anotherBits = Float.floatToIntBits(f2); 916 917 return (thisBits == anotherBits ? 0 : // Values are equal 918 (thisBits < anotherBits ? -1 : // (-0.0, 0.0) or (!NaN, NaN) 919 1)); // (0.0, -0.0) or (NaN, !NaN) 920 } 921 922 /** 923 * Adds two {@code float} values together as per the + operator. 924 * 925 * @param a the first operand 926 * @param b the second operand 927 * @return the sum of {@code a} and {@code b} 928 * @jls 4.2.4 Floating-Point Operations 929 * @see java.util.function.BinaryOperator 930 * @since 1.8 931 */ sum(float a, float b)932 public static float sum(float a, float b) { 933 return a + b; 934 } 935 936 /** 937 * Returns the greater of two {@code float} values 938 * as if by calling {@link Math#max(float, float) Math.max}. 939 * 940 * @param a the first operand 941 * @param b the second operand 942 * @return the greater of {@code a} and {@code b} 943 * @see java.util.function.BinaryOperator 944 * @since 1.8 945 */ max(float a, float b)946 public static float max(float a, float b) { 947 return Math.max(a, b); 948 } 949 950 /** 951 * Returns the smaller of two {@code float} values 952 * as if by calling {@link Math#min(float, float) Math.min}. 953 * 954 * @param a the first operand 955 * @param b the second operand 956 * @return the smaller of {@code a} and {@code b} 957 * @see java.util.function.BinaryOperator 958 * @since 1.8 959 */ min(float a, float b)960 public static float min(float a, float b) { 961 return Math.min(a, b); 962 } 963 964 /** use serialVersionUID from JDK 1.0.2 for interoperability */ 965 private static final long serialVersionUID = -2671257302660747028L; 966 } 967