001 /* Double.java -- object wrapper for double 002 Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005 003 Free Software Foundation, Inc. 004 005 This file is part of GNU Classpath. 006 007 GNU Classpath is free software; you can redistribute it and/or modify 008 it under the terms of the GNU General Public License as published by 009 the Free Software Foundation; either version 2, or (at your option) 010 any later version. 011 012 GNU Classpath is distributed in the hope that it will be useful, but 013 WITHOUT ANY WARRANTY; without even the implied warranty of 014 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 015 General Public License for more details. 016 017 You should have received a copy of the GNU General Public License 018 along with GNU Classpath; see the file COPYING. If not, write to the 019 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 020 02110-1301 USA. 021 022 Linking this library statically or dynamically with other modules is 023 making a combined work based on this library. Thus, the terms and 024 conditions of the GNU General Public License cover the whole 025 combination. 026 027 As a special exception, the copyright holders of this library give you 028 permission to link this library with independent modules to produce an 029 executable, regardless of the license terms of these independent 030 modules, and to copy and distribute the resulting executable under 031 terms of your choice, provided that you also meet, for each linked 032 independent module, the terms and conditions of the license of that 033 module. An independent module is a module which is not derived from 034 or based on this library. If you modify this library, you may extend 035 this exception to your version of the library, but you are not 036 obligated to do so. If you do not wish to do so, delete this 037 exception statement from your version. */ 038 039 package java.lang; 040 041 042 /** 043 * Instances of class <code>Double</code> represent primitive 044 * <code>double</code> values. 045 * 046 * Additionally, this class provides various helper functions and variables 047 * related to doubles. 048 * 049 * @author Paul Fisher 050 * @author Andrew Haley (aph@cygnus.com) 051 * @author Eric Blake (ebb9@email.byu.edu) 052 * @author Tom Tromey (tromey@redhat.com) 053 * @author Andrew John Hughes (gnu_andrew@member.fsf.org) 054 * @since 1.0 055 * @status partly updated to 1.5 056 */ 057 public final class Double extends Number implements Comparable<Double> 058 { 059 /** 060 * Compatible with JDK 1.0+. 061 */ 062 private static final long serialVersionUID = -9172774392245257468L; 063 064 /** 065 * The maximum positive value a <code>double</code> may represent 066 * is 1.7976931348623157e+308. 067 */ 068 public static final double MAX_VALUE = 1.7976931348623157e+308; 069 070 /** 071 * The minimum positive value a <code>double</code> may represent 072 * is 5e-324. 073 */ 074 public static final double MIN_VALUE = 5e-324; 075 076 /** 077 * The value of a double representation -1.0/0.0, negative 078 * infinity. 079 */ 080 public static final double NEGATIVE_INFINITY = -1.0 / 0.0; 081 082 /** 083 * The value of a double representing 1.0/0.0, positive infinity. 084 */ 085 public static final double POSITIVE_INFINITY = 1.0 / 0.0; 086 087 /** 088 * All IEEE 754 values of NaN have the same value in Java. 089 */ 090 public static final double NaN = 0.0 / 0.0; 091 092 /** 093 * The number of bits needed to represent a <code>double</code>. 094 * @since 1.5 095 */ 096 public static final int SIZE = 64; 097 098 /** 099 * The primitive type <code>double</code> is represented by this 100 * <code>Class</code> object. 101 * @since 1.1 102 */ 103 public static final Class<Double> TYPE = (Class<Double>) VMClassLoader.getPrimitiveClass('D'); 104 105 /** 106 * The immutable value of this Double. 107 * 108 * @serial the wrapped double 109 */ 110 private final double value; 111 112 /** 113 * Create a <code>Double</code> from the primitive <code>double</code> 114 * specified. 115 * 116 * @param value the <code>double</code> argument 117 */ 118 public Double(double value) 119 { 120 this.value = value; 121 } 122 123 /** 124 * Create a <code>Double</code> from the specified <code>String</code>. 125 * This method calls <code>Double.parseDouble()</code>. 126 * 127 * @param s the <code>String</code> to convert 128 * @throws NumberFormatException if <code>s</code> cannot be parsed as a 129 * <code>double</code> 130 * @throws NullPointerException if <code>s</code> is null 131 * @see #parseDouble(String) 132 */ 133 public Double(String s) 134 { 135 value = parseDouble(s); 136 } 137 138 /** 139 * Convert the <code>double</code> to a <code>String</code>. 140 * Floating-point string representation is fairly complex: here is a 141 * rundown of the possible values. "<code>[-]</code>" indicates that a 142 * negative sign will be printed if the value (or exponent) is negative. 143 * "<code><number></code>" means a string of digits ('0' to '9'). 144 * "<code><digit></code>" means a single digit ('0' to '9').<br> 145 * 146 * <table border=1> 147 * <tr><th>Value of Double</th><th>String Representation</th></tr> 148 * <tr><td>[+-] 0</td> <td><code>[-]0.0</code></td></tr> 149 * <tr><td>Between [+-] 10<sup>-3</sup> and 10<sup>7</sup>, exclusive</td> 150 * <td><code>[-]number.number</code></td></tr> 151 * <tr><td>Other numeric value</td> 152 * <td><code>[-]<digit>.<number> 153 * E[-]<number></code></td></tr> 154 * <tr><td>[+-] infinity</td> <td><code>[-]Infinity</code></td></tr> 155 * <tr><td>NaN</td> <td><code>NaN</code></td></tr> 156 * </table> 157 * 158 * Yes, negative zero <em>is</em> a possible value. Note that there is 159 * <em>always</em> a <code>.</code> and at least one digit printed after 160 * it: even if the number is 3, it will be printed as <code>3.0</code>. 161 * After the ".", all digits will be printed except trailing zeros. The 162 * result is rounded to the shortest decimal number which will parse back 163 * to the same double. 164 * 165 * <p>To create other output formats, use {@link java.text.NumberFormat}. 166 * 167 * @XXX specify where we are not in accord with the spec. 168 * 169 * @param d the <code>double</code> to convert 170 * @return the <code>String</code> representing the <code>double</code> 171 */ 172 public static String toString(double d) 173 { 174 return VMDouble.toString(d, false); 175 } 176 177 /** 178 * Convert a double value to a hexadecimal string. This converts as 179 * follows: 180 * <ul> 181 * <li> A NaN value is converted to the string "NaN". 182 * <li> Positive infinity is converted to the string "Infinity". 183 * <li> Negative infinity is converted to the string "-Infinity". 184 * <li> For all other values, the first character of the result is '-' 185 * if the value is negative. This is followed by '0x1.' if the 186 * value is normal, and '0x0.' if the value is denormal. This is 187 * then followed by a (lower-case) hexadecimal representation of the 188 * mantissa, with leading zeros as required for denormal values. 189 * The next character is a 'p', and this is followed by a decimal 190 * representation of the unbiased exponent. 191 * </ul> 192 * @param d the double value 193 * @return the hexadecimal string representation 194 * @since 1.5 195 */ 196 public static String toHexString(double d) 197 { 198 if (isNaN(d)) 199 return "NaN"; 200 if (isInfinite(d)) 201 return d < 0 ? "-Infinity" : "Infinity"; 202 203 long bits = doubleToLongBits(d); 204 StringBuilder result = new StringBuilder(); 205 206 if (bits < 0) 207 result.append('-'); 208 result.append("0x"); 209 210 final int mantissaBits = 52; 211 final int exponentBits = 11; 212 long mantMask = (1L << mantissaBits) - 1; 213 long mantissa = bits & mantMask; 214 long expMask = (1L << exponentBits) - 1; 215 long exponent = (bits >>> mantissaBits) & expMask; 216 217 result.append(exponent == 0 ? '0' : '1'); 218 result.append('.'); 219 result.append(Long.toHexString(mantissa)); 220 if (exponent == 0 && mantissa != 0) 221 { 222 // Treat denormal specially by inserting '0's to make 223 // the length come out right. The constants here are 224 // to account for things like the '0x'. 225 int offset = 4 + ((bits < 0) ? 1 : 0); 226 // The silly +3 is here to keep the code the same between 227 // the Float and Double cases. In Float the value is 228 // not a multiple of 4. 229 int desiredLength = offset + (mantissaBits + 3) / 4; 230 while (result.length() < desiredLength) 231 result.insert(offset, '0'); 232 } 233 result.append('p'); 234 if (exponent == 0 && mantissa == 0) 235 { 236 // Zero, so do nothing special. 237 } 238 else 239 { 240 // Apply bias. 241 boolean denormal = exponent == 0; 242 exponent -= (1 << (exponentBits - 1)) - 1; 243 // Handle denormal. 244 if (denormal) 245 ++exponent; 246 } 247 248 result.append(Long.toString(exponent)); 249 return result.toString(); 250 } 251 252 /** 253 * Returns a <code>Double</code> object wrapping the value. 254 * In contrast to the <code>Double</code> constructor, this method 255 * may cache some values. It is used by boxing conversion. 256 * 257 * @param val the value to wrap 258 * @return the <code>Double</code> 259 * @since 1.5 260 */ 261 public static Double valueOf(double val) 262 { 263 // We don't actually cache, but we could. 264 return new Double(val); 265 } 266 267 /** 268 * Create a new <code>Double</code> object using the <code>String</code>. 269 * 270 * @param s the <code>String</code> to convert 271 * @return the new <code>Double</code> 272 * @throws NumberFormatException if <code>s</code> cannot be parsed as a 273 * <code>double</code> 274 * @throws NullPointerException if <code>s</code> is null. 275 * @see #parseDouble(String) 276 */ 277 public static Double valueOf(String s) 278 { 279 return new Double(parseDouble(s)); 280 } 281 282 /** 283 * Parse the specified <code>String</code> as a <code>double</code>. The 284 * extended BNF grammar is as follows:<br> 285 * <pre> 286 * <em>DecodableString</em>: 287 * ( [ <code>-</code> | <code>+</code> ] <code>NaN</code> ) 288 * | ( [ <code>-</code> | <code>+</code> ] <code>Infinity</code> ) 289 * | ( [ <code>-</code> | <code>+</code> ] <em>FloatingPoint</em> 290 * [ <code>f</code> | <code>F</code> | <code>d</code> 291 * | <code>D</code>] ) 292 * <em>FloatingPoint</em>: 293 * ( { <em>Digit</em> }+ [ <code>.</code> { <em>Digit</em> } ] 294 * [ <em>Exponent</em> ] ) 295 * | ( <code>.</code> { <em>Digit</em> }+ [ <em>Exponent</em> ] ) 296 * <em>Exponent</em>: 297 * ( ( <code>e</code> | <code>E</code> ) 298 * [ <code>-</code> | <code>+</code> ] { <em>Digit</em> }+ ) 299 * <em>Digit</em>: <em><code>'0'</code> through <code>'9'</code></em> 300 * </pre> 301 * 302 * <p>NaN and infinity are special cases, to allow parsing of the output 303 * of toString. Otherwise, the result is determined by calculating 304 * <em>n * 10<sup>exponent</sup></em> to infinite precision, then rounding 305 * to the nearest double. Remember that many numbers cannot be precisely 306 * represented in floating point. In case of overflow, infinity is used, 307 * and in case of underflow, signed zero is used. Unlike Integer.parseInt, 308 * this does not accept Unicode digits outside the ASCII range. 309 * 310 * <p>If an unexpected character is found in the <code>String</code>, a 311 * <code>NumberFormatException</code> will be thrown. Leading and trailing 312 * 'whitespace' is ignored via <code>String.trim()</code>, but spaces 313 * internal to the actual number are not allowed. 314 * 315 * <p>To parse numbers according to another format, consider using 316 * {@link java.text.NumberFormat}. 317 * 318 * @XXX specify where/how we are not in accord with the spec. 319 * 320 * @param str the <code>String</code> to convert 321 * @return the <code>double</code> value of <code>s</code> 322 * @throws NumberFormatException if <code>s</code> cannot be parsed as a 323 * <code>double</code> 324 * @throws NullPointerException if <code>s</code> is null 325 * @see #MIN_VALUE 326 * @see #MAX_VALUE 327 * @see #POSITIVE_INFINITY 328 * @see #NEGATIVE_INFINITY 329 * @since 1.2 330 */ 331 public static double parseDouble(String str) 332 { 333 return VMDouble.parseDouble(str); 334 } 335 336 /** 337 * Return <code>true</code> if the <code>double</code> has the same 338 * value as <code>NaN</code>, otherwise return <code>false</code>. 339 * 340 * @param v the <code>double</code> to compare 341 * @return whether the argument is <code>NaN</code>. 342 */ 343 public static boolean isNaN(double v) 344 { 345 // This works since NaN != NaN is the only reflexive inequality 346 // comparison which returns true. 347 return v != v; 348 } 349 350 /** 351 * Return <code>true</code> if the <code>double</code> has a value 352 * equal to either <code>NEGATIVE_INFINITY</code> or 353 * <code>POSITIVE_INFINITY</code>, otherwise return <code>false</code>. 354 * 355 * @param v the <code>double</code> to compare 356 * @return whether the argument is (-/+) infinity. 357 */ 358 public static boolean isInfinite(double v) 359 { 360 return v == POSITIVE_INFINITY || v == NEGATIVE_INFINITY; 361 } 362 363 /** 364 * Return <code>true</code> if the value of this <code>Double</code> 365 * is the same as <code>NaN</code>, otherwise return <code>false</code>. 366 * 367 * @return whether this <code>Double</code> is <code>NaN</code> 368 */ 369 public boolean isNaN() 370 { 371 return isNaN(value); 372 } 373 374 /** 375 * Return <code>true</code> if the value of this <code>Double</code> 376 * is the same as <code>NEGATIVE_INFINITY</code> or 377 * <code>POSITIVE_INFINITY</code>, otherwise return <code>false</code>. 378 * 379 * @return whether this <code>Double</code> is (-/+) infinity 380 */ 381 public boolean isInfinite() 382 { 383 return isInfinite(value); 384 } 385 386 /** 387 * Convert the <code>double</code> value of this <code>Double</code> 388 * to a <code>String</code>. This method calls 389 * <code>Double.toString(double)</code> to do its dirty work. 390 * 391 * @return the <code>String</code> representation 392 * @see #toString(double) 393 */ 394 public String toString() 395 { 396 return toString(value); 397 } 398 399 /** 400 * Return the value of this <code>Double</code> as a <code>byte</code>. 401 * 402 * @return the byte value 403 * @since 1.1 404 */ 405 public byte byteValue() 406 { 407 return (byte) value; 408 } 409 410 /** 411 * Return the value of this <code>Double</code> as a <code>short</code>. 412 * 413 * @return the short value 414 * @since 1.1 415 */ 416 public short shortValue() 417 { 418 return (short) value; 419 } 420 421 /** 422 * Return the value of this <code>Double</code> as an <code>int</code>. 423 * 424 * @return the int value 425 */ 426 public int intValue() 427 { 428 return (int) value; 429 } 430 431 /** 432 * Return the value of this <code>Double</code> as a <code>long</code>. 433 * 434 * @return the long value 435 */ 436 public long longValue() 437 { 438 return (long) value; 439 } 440 441 /** 442 * Return the value of this <code>Double</code> as a <code>float</code>. 443 * 444 * @return the float value 445 */ 446 public float floatValue() 447 { 448 return (float) value; 449 } 450 451 /** 452 * Return the value of this <code>Double</code>. 453 * 454 * @return the double value 455 */ 456 public double doubleValue() 457 { 458 return value; 459 } 460 461 /** 462 * Return a hashcode representing this Object. <code>Double</code>'s hash 463 * code is calculated by:<br> 464 * <code>long v = Double.doubleToLongBits(doubleValue());<br> 465 * int hash = (int)(v^(v>>32))</code>. 466 * 467 * @return this Object's hash code 468 * @see #doubleToLongBits(double) 469 */ 470 public int hashCode() 471 { 472 long v = doubleToLongBits(value); 473 return (int) (v ^ (v >>> 32)); 474 } 475 476 /** 477 * Returns <code>true</code> if <code>obj</code> is an instance of 478 * <code>Double</code> and represents the same double value. Unlike comparing 479 * two doubles with <code>==</code>, this treats two instances of 480 * <code>Double.NaN</code> as equal, but treats <code>0.0</code> and 481 * <code>-0.0</code> as unequal. 482 * 483 * <p>Note that <code>d1.equals(d2)</code> is identical to 484 * <code>doubleToLongBits(d1.doubleValue()) == 485 * doubleToLongBits(d2.doubleValue())</code>. 486 * 487 * @param obj the object to compare 488 * @return whether the objects are semantically equal 489 */ 490 public boolean equals(Object obj) 491 { 492 if (! (obj instanceof Double)) 493 return false; 494 495 double d = ((Double) obj).value; 496 497 // Avoid call to native method. However, some implementations, like gcj, 498 // are better off using floatToIntBits(value) == floatToIntBits(f). 499 // Check common case first, then check NaN and 0. 500 if (value == d) 501 return (value != 0) || (1 / value == 1 / d); 502 return isNaN(value) && isNaN(d); 503 } 504 505 /** 506 * Convert the double to the IEEE 754 floating-point "double format" bit 507 * layout. Bit 63 (the most significant) is the sign bit, bits 62-52 508 * (masked by 0x7ff0000000000000L) represent the exponent, and bits 51-0 509 * (masked by 0x000fffffffffffffL) are the mantissa. This function 510 * collapses all versions of NaN to 0x7ff8000000000000L. The result of this 511 * function can be used as the argument to 512 * <code>Double.longBitsToDouble(long)</code> to obtain the original 513 * <code>double</code> value. 514 * 515 * @param value the <code>double</code> to convert 516 * @return the bits of the <code>double</code> 517 * @see #longBitsToDouble(long) 518 */ 519 public static long doubleToLongBits(double value) 520 { 521 return VMDouble.doubleToLongBits(value); 522 } 523 524 /** 525 * Convert the double to the IEEE 754 floating-point "double format" bit 526 * layout. Bit 63 (the most significant) is the sign bit, bits 62-52 527 * (masked by 0x7ff0000000000000L) represent the exponent, and bits 51-0 528 * (masked by 0x000fffffffffffffL) are the mantissa. This function 529 * leaves NaN alone, rather than collapsing to a canonical value. The 530 * result of this function can be used as the argument to 531 * <code>Double.longBitsToDouble(long)</code> to obtain the original 532 * <code>double</code> value. 533 * 534 * @param value the <code>double</code> to convert 535 * @return the bits of the <code>double</code> 536 * @see #longBitsToDouble(long) 537 */ 538 public static long doubleToRawLongBits(double value) 539 { 540 return VMDouble.doubleToRawLongBits(value); 541 } 542 543 /** 544 * Convert the argument in IEEE 754 floating-point "double format" bit 545 * layout to the corresponding float. Bit 63 (the most significant) is the 546 * sign bit, bits 62-52 (masked by 0x7ff0000000000000L) represent the 547 * exponent, and bits 51-0 (masked by 0x000fffffffffffffL) are the mantissa. 548 * This function leaves NaN alone, so that you can recover the bit pattern 549 * with <code>Double.doubleToRawLongBits(double)</code>. 550 * 551 * @param bits the bits to convert 552 * @return the <code>double</code> represented by the bits 553 * @see #doubleToLongBits(double) 554 * @see #doubleToRawLongBits(double) 555 */ 556 public static double longBitsToDouble(long bits) 557 { 558 return VMDouble.longBitsToDouble(bits); 559 } 560 561 /** 562 * Compare two Doubles numerically by comparing their <code>double</code> 563 * values. The result is positive if the first is greater, negative if the 564 * second is greater, and 0 if the two are equal. However, this special 565 * cases NaN and signed zero as follows: NaN is considered greater than 566 * all other doubles, including <code>POSITIVE_INFINITY</code>, and positive 567 * zero is considered greater than negative zero. 568 * 569 * @param d the Double to compare 570 * @return the comparison 571 * @since 1.2 572 */ 573 public int compareTo(Double d) 574 { 575 return compare(value, d.value); 576 } 577 578 /** 579 * Behaves like <code>new Double(x).compareTo(new Double(y))</code>; in 580 * other words this compares two doubles, special casing NaN and zero, 581 * without the overhead of objects. 582 * 583 * @param x the first double to compare 584 * @param y the second double to compare 585 * @return the comparison 586 * @since 1.4 587 */ 588 public static int compare(double x, double y) 589 { 590 if (isNaN(x)) 591 return isNaN(y) ? 0 : 1; 592 if (isNaN(y)) 593 return -1; 594 // recall that 0.0 == -0.0, so we convert to infinites and try again 595 if (x == 0 && y == 0) 596 return (int) (1 / x - 1 / y); 597 if (x == y) 598 return 0; 599 600 return x > y ? 1 : -1; 601 } 602 }