1 /* Float.java -- object wrapper for float 2 Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005 3 Free Software Foundation, Inc. 4 5 This file is part of GNU Classpath. 6 7 GNU Classpath is free software; you can redistribute it and/or modify 8 it under the terms of the GNU General Public License as published by 9 the Free Software Foundation; either version 2, or (at your option) 10 any later version. 11 12 GNU Classpath is distributed in the hope that it will be useful, but 13 WITHOUT ANY WARRANTY; without even the implied warranty of 14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 15 General Public License for more details. 16 17 You should have received a copy of the GNU General Public License 18 along with GNU Classpath; see the file COPYING. If not, write to the 19 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 20 02110-1301 USA. 21 22 Linking this library statically or dynamically with other modules is 23 making a combined work based on this library. Thus, the terms and 24 conditions of the GNU General Public License cover the whole 25 combination. 26 27 As a special exception, the copyright holders of this library give you 28 permission to link this library with independent modules to produce an 29 executable, regardless of the license terms of these independent 30 modules, and to copy and distribute the resulting executable under 31 terms of your choice, provided that you also meet, for each linked 32 independent module, the terms and conditions of the license of that 33 module. An independent module is a module which is not derived from 34 or based on this library. If you modify this library, you may extend 35 this exception to your version of the library, but you are not 36 obligated to do so. If you do not wish to do so, delete this 37 exception statement from your version. */ 38 39 40 package java.lang; 41 42 import gnu.java.lang.CPStringBuilder; 43 44 /** 45 * Instances of class <code>Float</code> represent primitive 46 * <code>float</code> values. 47 * 48 * Additionally, this class provides various helper functions and variables 49 * related to floats. 50 * 51 * @author Paul Fisher 52 * @author Andrew Haley (aph@cygnus.com) 53 * @author Eric Blake (ebb9@email.byu.edu) 54 * @author Tom Tromey (tromey@redhat.com) 55 * @author Andrew John Hughes (gnu_andrew@member.fsf.org) 56 * @since 1.0 57 * @status partly updated to 1.5 58 */ 59 public final class Float extends Number implements Comparable<Float> 60 { 61 /** 62 * Compatible with JDK 1.0+. 63 */ 64 private static final long serialVersionUID = -2671257302660747028L; 65 66 /** 67 * The maximum positive value a <code>double</code> may represent 68 * is 3.4028235e+38f. 69 */ 70 public static final float MAX_VALUE = 3.4028235e+38f; 71 72 /** 73 * The minimum positive value a <code>float</code> may represent 74 * is 1.4e-45. 75 */ 76 public static final float MIN_VALUE = 1.4e-45f; 77 78 /** 79 * The value of a float representation -1.0/0.0, negative infinity. 80 */ 81 public static final float NEGATIVE_INFINITY = -1.0f / 0.0f; 82 83 /** 84 * The value of a float representation 1.0/0.0, positive infinity. 85 */ 86 public static final float POSITIVE_INFINITY = 1.0f / 0.0f; 87 88 /** 89 * All IEEE 754 values of NaN have the same value in Java. 90 */ 91 public static final float NaN = 0.0f / 0.0f; 92 93 /** 94 * The primitive type <code>float</code> is represented by this 95 * <code>Class</code> object. 96 * @since 1.1 97 */ 98 public static final Class<Float> TYPE = (Class<Float>) VMClassLoader.getPrimitiveClass('F'); 99 100 /** 101 * The number of bits needed to represent a <code>float</code>. 102 * @since 1.5 103 */ 104 public static final int SIZE = 32; 105 106 /** 107 * Cache representation of 0 108 */ 109 private static final Float ZERO = new Float(0.0f); 110 111 /** 112 * Cache representation of 1 113 */ 114 private static final Float ONE = new Float(1.0f); 115 116 /** 117 * The immutable value of this Float. 118 * 119 * @serial the wrapped float 120 */ 121 private final float value; 122 123 /** 124 * Create a <code>Float</code> from the primitive <code>float</code> 125 * specified. 126 * 127 * @param value the <code>float</code> argument 128 */ Float(float value)129 public Float(float value) 130 { 131 this.value = value; 132 } 133 134 /** 135 * Create a <code>Float</code> from the primitive <code>double</code> 136 * specified. 137 * 138 * @param value the <code>double</code> argument 139 */ Float(double value)140 public Float(double value) 141 { 142 this.value = (float) value; 143 } 144 145 /** 146 * Create a <code>Float</code> from the specified <code>String</code>. 147 * This method calls <code>Float.parseFloat()</code>. 148 * 149 * @param s the <code>String</code> to convert 150 * @throws NumberFormatException if <code>s</code> cannot be parsed as a 151 * <code>float</code> 152 * @throws NullPointerException if <code>s</code> is null 153 * @see #parseFloat(String) 154 */ Float(String s)155 public Float(String s) 156 { 157 value = parseFloat(s); 158 } 159 160 /** 161 * Convert the <code>float</code> to a <code>String</code>. 162 * Floating-point string representation is fairly complex: here is a 163 * rundown of the possible values. "<code>[-]</code>" indicates that a 164 * negative sign will be printed if the value (or exponent) is negative. 165 * "<code><number></code>" means a string of digits ('0' to '9'). 166 * "<code><digit></code>" means a single digit ('0' to '9').<br> 167 * 168 * <table border=1> 169 * <tr><th>Value of Float</th><th>String Representation</th></tr> 170 * <tr><td>[+-] 0</td> <td><code>[-]0.0</code></td></tr> 171 * <tr><td>Between [+-] 10<sup>-3</sup> and 10<sup>7</sup>, exclusive</td> 172 * <td><code>[-]number.number</code></td></tr> 173 * <tr><td>Other numeric value</td> 174 * <td><code>[-]<digit>.<number> 175 * E[-]<number></code></td></tr> 176 * <tr><td>[+-] infinity</td> <td><code>[-]Infinity</code></td></tr> 177 * <tr><td>NaN</td> <td><code>NaN</code></td></tr> 178 * </table> 179 * 180 * Yes, negative zero <em>is</em> a possible value. Note that there is 181 * <em>always</em> a <code>.</code> and at least one digit printed after 182 * it: even if the number is 3, it will be printed as <code>3.0</code>. 183 * After the ".", all digits will be printed except trailing zeros. The 184 * result is rounded to the shortest decimal number which will parse back 185 * to the same float. 186 * 187 * <p>To create other output formats, use {@link java.text.NumberFormat}. 188 * 189 * @XXX specify where we are not in accord with the spec. 190 * 191 * @param f the <code>float</code> to convert 192 * @return the <code>String</code> representing the <code>float</code> 193 */ toString(float f)194 public static String toString(float f) 195 { 196 return VMFloat.toString(f); 197 } 198 199 /** 200 * Convert a float value to a hexadecimal string. This converts as 201 * follows: 202 * <ul> 203 * <li> A NaN value is converted to the string "NaN". 204 * <li> Positive infinity is converted to the string "Infinity". 205 * <li> Negative infinity is converted to the string "-Infinity". 206 * <li> For all other values, the first character of the result is '-' 207 * if the value is negative. This is followed by '0x1.' if the 208 * value is normal, and '0x0.' if the value is denormal. This is 209 * then followed by a (lower-case) hexadecimal representation of the 210 * mantissa, with leading zeros as required for denormal values. 211 * The next character is a 'p', and this is followed by a decimal 212 * representation of the unbiased exponent. 213 * </ul> 214 * @param f the float value 215 * @return the hexadecimal string representation 216 * @since 1.5 217 */ toHexString(float f)218 public static String toHexString(float f) 219 { 220 if (isNaN(f)) 221 return "NaN"; 222 if (isInfinite(f)) 223 return f < 0 ? "-Infinity" : "Infinity"; 224 225 int bits = floatToIntBits(f); 226 CPStringBuilder result = new CPStringBuilder(); 227 228 if (bits < 0) 229 result.append('-'); 230 result.append("0x"); 231 232 final int mantissaBits = 23; 233 final int exponentBits = 8; 234 int mantMask = (1 << mantissaBits) - 1; 235 int mantissa = bits & mantMask; 236 int expMask = (1 << exponentBits) - 1; 237 int exponent = (bits >>> mantissaBits) & expMask; 238 239 result.append(exponent == 0 ? '0' : '1'); 240 result.append('.'); 241 // For Float only, we have to adjust the mantissa. 242 mantissa <<= 1; 243 result.append(Integer.toHexString(mantissa)); 244 if (exponent == 0 && mantissa != 0) 245 { 246 // Treat denormal specially by inserting '0's to make 247 // the length come out right. The constants here are 248 // to account for things like the '0x'. 249 int offset = 4 + ((bits < 0) ? 1 : 0); 250 // The silly +3 is here to keep the code the same between 251 // the Float and Double cases. In Float the value is 252 // not a multiple of 4. 253 int desiredLength = offset + (mantissaBits + 3) / 4; 254 while (result.length() < desiredLength) 255 result.insert(offset, '0'); 256 } 257 result.append('p'); 258 if (exponent == 0 && mantissa == 0) 259 { 260 // Zero, so do nothing special. 261 } 262 else 263 { 264 // Apply bias. 265 boolean denormal = exponent == 0; 266 exponent -= (1 << (exponentBits - 1)) - 1; 267 // Handle denormal. 268 if (denormal) 269 ++exponent; 270 } 271 272 result.append(Integer.toString(exponent)); 273 return result.toString(); 274 } 275 276 /** 277 * Creates a new <code>Float</code> object using the <code>String</code>. 278 * 279 * @param s the <code>String</code> to convert 280 * @return the new <code>Float</code> 281 * @throws NumberFormatException if <code>s</code> cannot be parsed as a 282 * <code>float</code> 283 * @throws NullPointerException if <code>s</code> is null 284 * @see #parseFloat(String) 285 */ valueOf(String s)286 public static Float valueOf(String s) 287 { 288 return valueOf(parseFloat(s)); 289 } 290 291 /** 292 * Returns a <code>Float</code> object wrapping the value. 293 * In contrast to the <code>Float</code> constructor, this method 294 * may cache some values. It is used by boxing conversion. 295 * 296 * @param val the value to wrap 297 * @return the <code>Float</code> 298 * @since 1.5 299 */ valueOf(float val)300 public static Float valueOf(float val) 301 { 302 if ((val == 0.0) && (floatToRawIntBits(val) == 0)) 303 return ZERO; 304 else if (val == 1.0) 305 return ONE; 306 else 307 return new Float(val); 308 } 309 310 /** 311 * Parse the specified <code>String</code> as a <code>float</code>. The 312 * extended BNF grammar is as follows:<br> 313 * <pre> 314 * <em>DecodableString</em>: 315 * ( [ <code>-</code> | <code>+</code> ] <code>NaN</code> ) 316 * | ( [ <code>-</code> | <code>+</code> ] <code>Infinity</code> ) 317 * | ( [ <code>-</code> | <code>+</code> ] <em>FloatingPoint</em> 318 * [ <code>f</code> | <code>F</code> | <code>d</code> 319 * | <code>D</code>] ) 320 * <em>FloatingPoint</em>: 321 * ( { <em>Digit</em> }+ [ <code>.</code> { <em>Digit</em> } ] 322 * [ <em>Exponent</em> ] ) 323 * | ( <code>.</code> { <em>Digit</em> }+ [ <em>Exponent</em> ] ) 324 * <em>Exponent</em>: 325 * ( ( <code>e</code> | <code>E</code> ) 326 * [ <code>-</code> | <code>+</code> ] { <em>Digit</em> }+ ) 327 * <em>Digit</em>: <em><code>'0'</code> through <code>'9'</code></em> 328 * </pre> 329 * 330 * <p>NaN and infinity are special cases, to allow parsing of the output 331 * of toString. Otherwise, the result is determined by calculating 332 * <em>n * 10<sup>exponent</sup></em> to infinite precision, then rounding 333 * to the nearest float. Remember that many numbers cannot be precisely 334 * represented in floating point. In case of overflow, infinity is used, 335 * and in case of underflow, signed zero is used. Unlike Integer.parseInt, 336 * this does not accept Unicode digits outside the ASCII range. 337 * 338 * <p>If an unexpected character is found in the <code>String</code>, a 339 * <code>NumberFormatException</code> will be thrown. Leading and trailing 340 * 'whitespace' is ignored via <code>String.trim()</code>, but spaces 341 * internal to the actual number are not allowed. 342 * 343 * <p>To parse numbers according to another format, consider using 344 * {@link java.text.NumberFormat}. 345 * 346 * @XXX specify where/how we are not in accord with the spec. 347 * 348 * @param str the <code>String</code> to convert 349 * @return the <code>float</code> value of <code>s</code> 350 * @throws NumberFormatException if <code>str</code> cannot be parsed as a 351 * <code>float</code> 352 * @throws NullPointerException if <code>str</code> is null 353 * @see #MIN_VALUE 354 * @see #MAX_VALUE 355 * @see #POSITIVE_INFINITY 356 * @see #NEGATIVE_INFINITY 357 * @since 1.2 358 */ parseFloat(String str)359 public static float parseFloat(String str) 360 { 361 return VMFloat.parseFloat(str); 362 } 363 364 /** 365 * Return <code>true</code> if the <code>float</code> has the same 366 * value as <code>NaN</code>, otherwise return <code>false</code>. 367 * 368 * @param v the <code>float</code> to compare 369 * @return whether the argument is <code>NaN</code> 370 */ isNaN(float v)371 public static boolean isNaN(float v) 372 { 373 // This works since NaN != NaN is the only reflexive inequality 374 // comparison which returns true. 375 return v != v; 376 } 377 378 /** 379 * Return <code>true</code> if the <code>float</code> has a value 380 * equal to either <code>NEGATIVE_INFINITY</code> or 381 * <code>POSITIVE_INFINITY</code>, otherwise return <code>false</code>. 382 * 383 * @param v the <code>float</code> to compare 384 * @return whether the argument is (-/+) infinity 385 */ isInfinite(float v)386 public static boolean isInfinite(float v) 387 { 388 return v == POSITIVE_INFINITY || v == NEGATIVE_INFINITY; 389 } 390 391 /** 392 * Return <code>true</code> if the value of this <code>Float</code> 393 * is the same as <code>NaN</code>, otherwise return <code>false</code>. 394 * 395 * @return whether this <code>Float</code> is <code>NaN</code> 396 */ isNaN()397 public boolean isNaN() 398 { 399 return isNaN(value); 400 } 401 402 /** 403 * Return <code>true</code> if the value of this <code>Float</code> 404 * is the same as <code>NEGATIVE_INFINITY</code> or 405 * <code>POSITIVE_INFINITY</code>, otherwise return <code>false</code>. 406 * 407 * @return whether this <code>Float</code> is (-/+) infinity 408 */ isInfinite()409 public boolean isInfinite() 410 { 411 return isInfinite(value); 412 } 413 414 /** 415 * Convert the <code>float</code> value of this <code>Float</code> 416 * to a <code>String</code>. This method calls 417 * <code>Float.toString(float)</code> to do its dirty work. 418 * 419 * @return the <code>String</code> representation 420 * @see #toString(float) 421 */ toString()422 public String toString() 423 { 424 return toString(value); 425 } 426 427 /** 428 * Return the value of this <code>Float</code> as a <code>byte</code>. 429 * 430 * @return the byte value 431 * @since 1.1 432 */ byteValue()433 public byte byteValue() 434 { 435 return (byte) value; 436 } 437 438 /** 439 * Return the value of this <code>Float</code> as a <code>short</code>. 440 * 441 * @return the short value 442 * @since 1.1 443 */ shortValue()444 public short shortValue() 445 { 446 return (short) value; 447 } 448 449 /** 450 * Return the value of this <code>Integer</code> as an <code>int</code>. 451 * 452 * @return the int value 453 */ intValue()454 public int intValue() 455 { 456 return (int) value; 457 } 458 459 /** 460 * Return the value of this <code>Integer</code> as a <code>long</code>. 461 * 462 * @return the long value 463 */ longValue()464 public long longValue() 465 { 466 return (long) value; 467 } 468 469 /** 470 * Return the value of this <code>Float</code>. 471 * 472 * @return the float value 473 */ floatValue()474 public float floatValue() 475 { 476 return value; 477 } 478 479 /** 480 * Return the value of this <code>Float</code> as a <code>double</code> 481 * 482 * @return the double value 483 */ doubleValue()484 public double doubleValue() 485 { 486 return value; 487 } 488 489 /** 490 * Return a hashcode representing this Object. <code>Float</code>'s hash 491 * code is calculated by calling <code>floatToIntBits(floatValue())</code>. 492 * 493 * @return this Object's hash code 494 * @see #floatToIntBits(float) 495 */ hashCode()496 public int hashCode() 497 { 498 return floatToIntBits(value); 499 } 500 501 /** 502 * Returns <code>true</code> if <code>obj</code> is an instance of 503 * <code>Float</code> and represents the same float value. Unlike comparing 504 * two floats with <code>==</code>, this treats two instances of 505 * <code>Float.NaN</code> as equal, but treats <code>0.0</code> and 506 * <code>-0.0</code> as unequal. 507 * 508 * <p>Note that <code>f1.equals(f2)</code> is identical to 509 * <code>floatToIntBits(f1.floatValue()) == 510 * floatToIntBits(f2.floatValue())</code>. 511 * 512 * @param obj the object to compare 513 * @return whether the objects are semantically equal 514 */ equals(Object obj)515 public boolean equals(Object obj) 516 { 517 if (obj instanceof Float) 518 { 519 float f = ((Float) obj).value; 520 return (floatToRawIntBits(value) == floatToRawIntBits(f)) || 521 (isNaN(value) && isNaN(f)); 522 } 523 return false; 524 } 525 526 /** 527 * Convert the float to the IEEE 754 floating-point "single format" bit 528 * layout. Bit 31 (the most significant) is the sign bit, bits 30-23 529 * (masked by 0x7f800000) represent the exponent, and bits 22-0 530 * (masked by 0x007fffff) are the mantissa. This function collapses all 531 * versions of NaN to 0x7fc00000. The result of this function can be used 532 * as the argument to <code>Float.intBitsToFloat(int)</code> to obtain the 533 * original <code>float</code> value. 534 * 535 * @param value the <code>float</code> to convert 536 * @return the bits of the <code>float</code> 537 * @see #intBitsToFloat(int) 538 */ floatToIntBits(float value)539 public static int floatToIntBits(float value) 540 { 541 if (isNaN(value)) 542 return 0x7fc00000; 543 else 544 return VMFloat.floatToRawIntBits(value); 545 } 546 547 /** 548 * Convert the float to the IEEE 754 floating-point "single format" bit 549 * layout. Bit 31 (the most significant) is the sign bit, bits 30-23 550 * (masked by 0x7f800000) represent the exponent, and bits 22-0 551 * (masked by 0x007fffff) are the mantissa. This function leaves NaN alone, 552 * rather than collapsing to a canonical value. The result of this function 553 * can be used as the argument to <code>Float.intBitsToFloat(int)</code> to 554 * obtain the original <code>float</code> value. 555 * 556 * @param value the <code>float</code> to convert 557 * @return the bits of the <code>float</code> 558 * @see #intBitsToFloat(int) 559 */ floatToRawIntBits(float value)560 public static int floatToRawIntBits(float value) 561 { 562 return VMFloat.floatToRawIntBits(value); 563 } 564 565 /** 566 * Convert the argument in IEEE 754 floating-point "single format" bit 567 * layout to the corresponding float. Bit 31 (the most significant) is the 568 * sign bit, bits 30-23 (masked by 0x7f800000) represent the exponent, and 569 * bits 22-0 (masked by 0x007fffff) are the mantissa. This function leaves 570 * NaN alone, so that you can recover the bit pattern with 571 * <code>Float.floatToRawIntBits(float)</code>. 572 * 573 * @param bits the bits to convert 574 * @return the <code>float</code> represented by the bits 575 * @see #floatToIntBits(float) 576 * @see #floatToRawIntBits(float) 577 */ intBitsToFloat(int bits)578 public static float intBitsToFloat(int bits) 579 { 580 return VMFloat.intBitsToFloat(bits); 581 } 582 583 /** 584 * Compare two Floats numerically by comparing their <code>float</code> 585 * values. The result is positive if the first is greater, negative if the 586 * second is greater, and 0 if the two are equal. However, this special 587 * cases NaN and signed zero as follows: NaN is considered greater than 588 * all other floats, including <code>POSITIVE_INFINITY</code>, and positive 589 * zero is considered greater than negative zero. 590 * 591 * @param f the Float to compare 592 * @return the comparison 593 * @since 1.2 594 */ compareTo(Float f)595 public int compareTo(Float f) 596 { 597 return compare(value, f.value); 598 } 599 600 /** 601 * Behaves like <code>new Float(x).compareTo(new Float(y))</code>; in 602 * other words this compares two floats, special casing NaN and zero, 603 * without the overhead of objects. 604 * 605 * @param x the first float to compare 606 * @param y the second float to compare 607 * @return the comparison 608 * @since 1.4 609 */ compare(float x, float y)610 public static int compare(float x, float y) 611 { 612 // handle the easy cases: 613 if (x < y) 614 return -1; 615 if (x > y) 616 return 1; 617 618 // handle equality respecting that 0.0 != -0.0 (hence not using x == y): 619 int ix = floatToRawIntBits(x); 620 int iy = floatToRawIntBits(y); 621 if (ix == iy) 622 return 0; 623 624 // handle NaNs: 625 if (x != x) 626 return (y != y) ? 0 : 1; 627 else if (y != y) 628 return -1; 629 630 // handle +/- 0.0 631 return (ix < iy) ? -1 : 1; 632 } 633 } 634