Source for java.lang.Double

   1: /* Double.java -- object wrapper for double
   2:    Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 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: package java.lang;
  40: 
  41: 
  42: /**
  43:  * Instances of class <code>Double</code> represent primitive
  44:  * <code>double</code> values.
  45:  *
  46:  * Additionally, this class provides various helper functions and variables
  47:  * related to doubles.
  48:  *
  49:  * @author Paul Fisher
  50:  * @author Andrew Haley (aph@cygnus.com)
  51:  * @author Eric Blake (ebb9@email.byu.edu)
  52:  * @since 1.0
  53:  * @status updated to 1.4
  54:  */
  55: public final class Double extends Number implements Comparable
  56: {
  57:   /**
  58:    * Compatible with JDK 1.0+.
  59:    */
  60:   private static final long serialVersionUID = -9172774392245257468L;
  61: 
  62:   /**
  63:    * The maximum positive value a <code>double</code> may represent
  64:    * is 1.7976931348623157e+308.
  65:    */
  66:   public static final double MAX_VALUE = 1.7976931348623157e+308;
  67: 
  68:   /**
  69:    * The minimum positive value a <code>double</code> may represent
  70:    * is 5e-324.
  71:    */
  72:   public static final double MIN_VALUE = 5e-324;
  73: 
  74:   /**
  75:    * The value of a double representation -1.0/0.0, negative
  76:    * infinity.
  77:    */
  78:   public static final double NEGATIVE_INFINITY = -1.0 / 0.0;
  79: 
  80:   /**
  81:    * The value of a double representing 1.0/0.0, positive infinity.
  82:    */
  83:   public static final double POSITIVE_INFINITY = 1.0 / 0.0;
  84: 
  85:   /**
  86:    * All IEEE 754 values of NaN have the same value in Java.
  87:    */
  88:   public static final double NaN = 0.0 / 0.0;
  89: 
  90:   /**
  91:    * The number of bits needed to represent a <code>double</code>.
  92:    * @since 1.5
  93:    */
  94:   public static final int SIZE = 64;
  95: 
  96:  /**
  97:    * The primitive type <code>double</code> is represented by this
  98:    * <code>Class</code> object.
  99:    * @since 1.1
 100:    */
 101:   public static final Class TYPE = VMClassLoader.getPrimitiveClass('D');
 102: 
 103:   /**
 104:    * The immutable value of this Double.
 105:    *
 106:    * @serial the wrapped double
 107:    */
 108:   private final double value;
 109: 
 110:   /**
 111:    * Create a <code>Double</code> from the primitive <code>double</code>
 112:    * specified.
 113:    *
 114:    * @param value the <code>double</code> argument
 115:    */
 116:   public Double(double value)
 117:   {
 118:     this.value = value;
 119:   }
 120: 
 121:   /**
 122:    * Create a <code>Double</code> from the specified <code>String</code>.
 123:    * This method calls <code>Double.parseDouble()</code>.
 124:    *
 125:    * @param s the <code>String</code> to convert
 126:    * @throws NumberFormatException if <code>s</code> cannot be parsed as a
 127:    *         <code>double</code>
 128:    * @throws NullPointerException if <code>s</code> is null
 129:    * @see #parseDouble(String)
 130:    */
 131:   public Double(String s)
 132:   {
 133:     value = parseDouble(s);
 134:   }
 135: 
 136:   /**
 137:    * Convert the <code>double</code> to a <code>String</code>.
 138:    * Floating-point string representation is fairly complex: here is a
 139:    * rundown of the possible values.  "<code>[-]</code>" indicates that a
 140:    * negative sign will be printed if the value (or exponent) is negative.
 141:    * "<code>&lt;number&gt;</code>" means a string of digits ('0' to '9').
 142:    * "<code>&lt;digit&gt;</code>" means a single digit ('0' to '9').<br>
 143:    *
 144:    * <table border=1>
 145:    * <tr><th>Value of Double</th><th>String Representation</th></tr>
 146:    * <tr><td>[+-] 0</td> <td><code>[-]0.0</code></td></tr>
 147:    * <tr><td>Between [+-] 10<sup>-3</sup> and 10<sup>7</sup>, exclusive</td>
 148:    *     <td><code>[-]number.number</code></td></tr>
 149:    * <tr><td>Other numeric value</td>
 150:    *     <td><code>[-]&lt;digit&gt;.&lt;number&gt;
 151:    *          E[-]&lt;number&gt;</code></td></tr>
 152:    * <tr><td>[+-] infinity</td> <td><code>[-]Infinity</code></td></tr>
 153:    * <tr><td>NaN</td> <td><code>NaN</code></td></tr>
 154:    * </table>
 155:    *
 156:    * Yes, negative zero <em>is</em> a possible value.  Note that there is
 157:    * <em>always</em> a <code>.</code> and at least one digit printed after
 158:    * it: even if the number is 3, it will be printed as <code>3.0</code>.
 159:    * After the ".", all digits will be printed except trailing zeros. The
 160:    * result is rounded to the shortest decimal number which will parse back
 161:    * to the same double.
 162:    *
 163:    * <p>To create other output formats, use {@link java.text.NumberFormat}.
 164:    *
 165:    * @XXX specify where we are not in accord with the spec.
 166:    *
 167:    * @param d the <code>double</code> to convert
 168:    * @return the <code>String</code> representing the <code>double</code>
 169:    */
 170:   public static String toString(double d)
 171:   {
 172:     return VMDouble.toString(d, false);
 173:   }
 174: 
 175:   /**
 176:    * Convert a double value to a hexadecimal string.  This converts as
 177:    * follows:
 178:    * <ul>
 179:    * <li> A NaN value is converted to the string "NaN".
 180:    * <li> Positive infinity is converted to the string "Infinity".
 181:    * <li> Negative infinity is converted to the string "-Infinity".
 182:    * <li> For all other values, the first character of the result is '-'
 183:    * if the value is negative.  This is followed by '0x1.' if the
 184:    * value is normal, and '0x0.' if the value is denormal.  This is
 185:    * then followed by a (lower-case) hexadecimal representation of the
 186:    * mantissa, with leading zeros as required for denormal values.
 187:    * The next character is a 'p', and this is followed by a decimal
 188:    * representation of the unbiased exponent.
 189:    * </ul>
 190:    * @param d the double value
 191:    * @return the hexadecimal string representation
 192:    * @since 1.5
 193:    */
 194:   public static String toHexString(double d)
 195:   {
 196:     if (isNaN(d))
 197:       return "NaN";
 198:     if (isInfinite(d))
 199:       return d < 0 ? "-Infinity" : "Infinity";
 200: 
 201:     long bits = doubleToLongBits(d);
 202:     StringBuilder result = new StringBuilder();
 203:     
 204:     if (bits < 0)
 205:       result.append('-');
 206:     result.append("0x");
 207: 
 208:     final int mantissaBits = 52;
 209:     final int exponentBits = 11;
 210:     long mantMask = (1L << mantissaBits) - 1;
 211:     long mantissa = bits & mantMask;
 212:     long expMask = (1L << exponentBits) - 1;
 213:     long exponent = (bits >>> mantissaBits) & expMask;
 214: 
 215:     result.append(exponent == 0 ? '0' : '1');
 216:     result.append('.');
 217:     result.append(Long.toHexString(mantissa));
 218:     if (exponent == 0 && mantissa != 0)
 219:       {
 220:         // Treat denormal specially by inserting '0's to make
 221:         // the length come out right.  The constants here are
 222:         // to account for things like the '0x'.
 223:         int offset = 4 + ((bits < 0) ? 1 : 0);
 224:         // The silly +3 is here to keep the code the same between
 225:         // the Float and Double cases.  In Float the value is
 226:         // not a multiple of 4.
 227:         int desiredLength = offset + (mantissaBits + 3) / 4;
 228:         while (result.length() < desiredLength)
 229:           result.insert(offset, '0');
 230:       }
 231:     result.append('p');
 232:     if (exponent == 0 && mantissa == 0)
 233:       {
 234:         // Zero, so do nothing special.
 235:       }
 236:     else
 237:       {
 238:         // Apply bias.
 239:         boolean denormal = exponent == 0;
 240:         exponent -= (1 << (exponentBits - 1)) - 1;
 241:         // Handle denormal.
 242:         if (denormal)
 243:           ++exponent;
 244:       }
 245: 
 246:     result.append(Long.toString(exponent));
 247:     return result.toString();
 248:   }
 249: 
 250:   /**
 251:    * Returns a <code>Double</code> object wrapping the value.
 252:    * In contrast to the <code>Double</code> constructor, this method
 253:    * may cache some values.  It is used by boxing conversion.
 254:    *
 255:    * @param val the value to wrap
 256:    * @return the <code>Double</code>
 257:    * 
 258:    * @since 1.5
 259:    */
 260:   public static Double valueOf(double val)
 261:   {
 262:     // We don't actually cache, but we could.
 263:     return new Double(val);
 264:   }
 265: 
 266:  /**
 267:    * Create a new <code>Double</code> object using the <code>String</code>.
 268:    *
 269:    * @param s the <code>String</code> to convert
 270:    * @return the new <code>Double</code>
 271:    * @throws NumberFormatException if <code>s</code> cannot be parsed as a
 272:    *         <code>double</code>
 273:    * @throws NullPointerException if <code>s</code> is null.
 274:    * @see #parseDouble(String)
 275:    */
 276:   public static Double valueOf(String s)
 277:   {
 278:     return new Double(parseDouble(s));
 279:   }
 280: 
 281:   /**
 282:    * Parse the specified <code>String</code> as a <code>double</code>. The
 283:    * extended BNF grammar is as follows:<br>
 284:    * <pre>
 285:    * <em>DecodableString</em>:
 286:    *      ( [ <code>-</code> | <code>+</code> ] <code>NaN</code> )
 287:    *    | ( [ <code>-</code> | <code>+</code> ] <code>Infinity</code> )
 288:    *    | ( [ <code>-</code> | <code>+</code> ] <em>FloatingPoint</em>
 289:    *              [ <code>f</code> | <code>F</code> | <code>d</code>
 290:    *                | <code>D</code>] )
 291:    * <em>FloatingPoint</em>:
 292:    *      ( { <em>Digit</em> }+ [ <code>.</code> { <em>Digit</em> } ]
 293:    *              [ <em>Exponent</em> ] )
 294:    *    | ( <code>.</code> { <em>Digit</em> }+ [ <em>Exponent</em> ] )
 295:    * <em>Exponent</em>:
 296:    *      ( ( <code>e</code> | <code>E</code> )
 297:    *              [ <code>-</code> | <code>+</code> ] { <em>Digit</em> }+ )
 298:    * <em>Digit</em>: <em><code>'0'</code> through <code>'9'</code></em>
 299:    * </pre>
 300:    *
 301:    * <p>NaN and infinity are special cases, to allow parsing of the output
 302:    * of toString.  Otherwise, the result is determined by calculating
 303:    * <em>n * 10<sup>exponent</sup></em> to infinite precision, then rounding
 304:    * to the nearest double. Remember that many numbers cannot be precisely
 305:    * represented in floating point. In case of overflow, infinity is used,
 306:    * and in case of underflow, signed zero is used. Unlike Integer.parseInt,
 307:    * this does not accept Unicode digits outside the ASCII range.
 308:    *
 309:    * <p>If an unexpected character is found in the <code>String</code>, a
 310:    * <code>NumberFormatException</code> will be thrown.  Leading and trailing
 311:    * 'whitespace' is ignored via <code>String.trim()</code>, but spaces
 312:    * internal to the actual number are not allowed.
 313:    *
 314:    * <p>To parse numbers according to another format, consider using
 315:    * {@link java.text.NumberFormat}.
 316:    *
 317:    * @XXX specify where/how we are not in accord with the spec.
 318:    *
 319:    * @param str the <code>String</code> to convert
 320:    * @return the <code>double</code> value of <code>s</code>
 321:    * @throws NumberFormatException if <code>s</code> cannot be parsed as a
 322:    *         <code>double</code>
 323:    * @throws NullPointerException if <code>s</code> is null
 324:    * @see #MIN_VALUE
 325:    * @see #MAX_VALUE
 326:    * @see #POSITIVE_INFINITY
 327:    * @see #NEGATIVE_INFINITY
 328:    * @since 1.2
 329:    */
 330:   public static double parseDouble(String str)
 331:   {
 332:     return VMDouble.parseDouble(str);
 333:   }
 334: 
 335:   /**
 336:    * Return <code>true</code> if the <code>double</code> has the same
 337:    * value as <code>NaN</code>, otherwise return <code>false</code>.
 338:    *
 339:    * @param v the <code>double</code> to compare
 340:    * @return whether the argument is <code>NaN</code>.
 341:    */
 342:   public static boolean isNaN(double v)
 343:   {
 344:     // This works since NaN != NaN is the only reflexive inequality
 345:     // comparison which returns true.
 346:     return v != v;
 347:   }
 348: 
 349:   /**
 350:    * Return <code>true</code> if the <code>double</code> has a value
 351:    * equal to either <code>NEGATIVE_INFINITY</code> or
 352:    * <code>POSITIVE_INFINITY</code>, otherwise return <code>false</code>.
 353:    *
 354:    * @param v the <code>double</code> to compare
 355:    * @return whether the argument is (-/+) infinity.
 356:    */
 357:   public static boolean isInfinite(double v)
 358:   {
 359:     return v == POSITIVE_INFINITY || v == NEGATIVE_INFINITY;
 360:   }
 361: 
 362:   /**
 363:    * Return <code>true</code> if the value of this <code>Double</code>
 364:    * is the same as <code>NaN</code>, otherwise return <code>false</code>.
 365:    *
 366:    * @return whether this <code>Double</code> is <code>NaN</code>
 367:    */
 368:   public boolean isNaN()
 369:   {
 370:     return isNaN(value);
 371:   }
 372: 
 373:   /**
 374:    * Return <code>true</code> if the value of this <code>Double</code>
 375:    * is the same as <code>NEGATIVE_INFINITY</code> or
 376:    * <code>POSITIVE_INFINITY</code>, otherwise return <code>false</code>.
 377:    *
 378:    * @return whether this <code>Double</code> is (-/+) infinity
 379:    */
 380:   public boolean isInfinite()
 381:   {
 382:     return isInfinite(value);
 383:   }
 384: 
 385:   /**
 386:    * Convert the <code>double</code> value of this <code>Double</code>
 387:    * to a <code>String</code>.  This method calls
 388:    * <code>Double.toString(double)</code> to do its dirty work.
 389:    *
 390:    * @return the <code>String</code> representation
 391:    * @see #toString(double)
 392:    */
 393:   public String toString()
 394:   {
 395:     return toString(value);
 396:   }
 397: 
 398:   /**
 399:    * Return the value of this <code>Double</code> as a <code>byte</code>.
 400:    *
 401:    * @return the byte value
 402:    * @since 1.1
 403:    */
 404:   public byte byteValue()
 405:   {
 406:     return (byte) value;
 407:   }
 408: 
 409:   /**
 410:    * Return the value of this <code>Double</code> as a <code>short</code>.
 411:    *
 412:    * @return the short value
 413:    * @since 1.1
 414:    */
 415:   public short shortValue()
 416:   {
 417:     return (short) value;
 418:   }
 419: 
 420:   /**
 421:    * Return the value of this <code>Double</code> as an <code>int</code>.
 422:    *
 423:    * @return the int value
 424:    */
 425:   public int intValue()
 426:   {
 427:     return (int) value;
 428:   }
 429: 
 430:   /**
 431:    * Return the value of this <code>Double</code> as a <code>long</code>.
 432:    *
 433:    * @return the long value
 434:    */
 435:   public long longValue()
 436:   {
 437:     return (long) value;
 438:   }
 439: 
 440:   /**
 441:    * Return the value of this <code>Double</code> as a <code>float</code>.
 442:    *
 443:    * @return the float value
 444:    */
 445:   public float floatValue()
 446:   {
 447:     return (float) value;
 448:   }
 449: 
 450:   /**
 451:    * Return the value of this <code>Double</code>.
 452:    *
 453:    * @return the double value
 454:    */
 455:   public double doubleValue()
 456:   {
 457:     return value;
 458:   }
 459: 
 460:   /**
 461:    * Return a hashcode representing this Object. <code>Double</code>'s hash
 462:    * code is calculated by:<br>
 463:    * <code>long v = Double.doubleToLongBits(doubleValue());<br>
 464:    *    int hash = (int)(v^(v&gt;&gt;32))</code>.
 465:    *
 466:    * @return this Object's hash code
 467:    * @see #doubleToLongBits(double)
 468:    */
 469:   public int hashCode()
 470:   {
 471:     long v = doubleToLongBits(value);
 472:     return (int) (v ^ (v >>> 32));
 473:   }
 474: 
 475:   /**
 476:    * Returns <code>true</code> if <code>obj</code> is an instance of
 477:    * <code>Double</code> and represents the same double value. Unlike comparing
 478:    * two doubles with <code>==</code>, this treats two instances of
 479:    * <code>Double.NaN</code> as equal, but treats <code>0.0</code> and
 480:    * <code>-0.0</code> as unequal.
 481:    *
 482:    * <p>Note that <code>d1.equals(d2)</code> is identical to
 483:    * <code>doubleToLongBits(d1.doubleValue()) ==
 484:    *    doubleToLongBits(d2.doubleValue())</code>.
 485:    *
 486:    * @param obj the object to compare
 487:    * @return whether the objects are semantically equal
 488:    */
 489:   public boolean equals(Object obj)
 490:   {
 491:     if (! (obj instanceof Double))
 492:       return false;
 493: 
 494:     double d = ((Double) obj).value;
 495: 
 496:     // Avoid call to native method. However, some implementations, like gcj,
 497:     // are better off using floatToIntBits(value) == floatToIntBits(f).
 498:     // Check common case first, then check NaN and 0.
 499:     if (value == d)
 500:       return (value != 0) || (1 / value == 1 / d);
 501:     return isNaN(value) && isNaN(d);
 502:   }
 503: 
 504:   /**
 505:    * Convert the double to the IEEE 754 floating-point "double format" bit
 506:    * layout. Bit 63 (the most significant) is the sign bit, bits 62-52
 507:    * (masked by 0x7ff0000000000000L) represent the exponent, and bits 51-0
 508:    * (masked by 0x000fffffffffffffL) are the mantissa. This function
 509:    * collapses all versions of NaN to 0x7ff8000000000000L. The result of this
 510:    * function can be used as the argument to
 511:    * <code>Double.longBitsToDouble(long)</code> to obtain the original
 512:    * <code>double</code> value.
 513:    *
 514:    * @param value the <code>double</code> to convert
 515:    * @return the bits of the <code>double</code>
 516:    * @see #longBitsToDouble(long)
 517:    */
 518:   public static long doubleToLongBits(double value)
 519:   {
 520:     return VMDouble.doubleToLongBits(value);
 521:   }
 522: 
 523:   /**
 524:    * Convert the double to the IEEE 754 floating-point "double format" bit
 525:    * layout. Bit 63 (the most significant) is the sign bit, bits 62-52
 526:    * (masked by 0x7ff0000000000000L) represent the exponent, and bits 51-0
 527:    * (masked by 0x000fffffffffffffL) are the mantissa. This function
 528:    * leaves NaN alone, rather than collapsing to a canonical value. The
 529:    * result of this function can be used as the argument to
 530:    * <code>Double.longBitsToDouble(long)</code> to obtain the original
 531:    * <code>double</code> value.
 532:    *
 533:    * @param value the <code>double</code> to convert
 534:    * @return the bits of the <code>double</code>
 535:    * @see #longBitsToDouble(long)
 536:    */
 537:   public static long doubleToRawLongBits(double value)
 538:   {
 539:     return VMDouble.doubleToRawLongBits(value);
 540:   }
 541: 
 542:   /**
 543:    * Convert the argument in IEEE 754 floating-point "double format" bit
 544:    * layout to the corresponding float. Bit 63 (the most significant) is the
 545:    * sign bit, bits 62-52 (masked by 0x7ff0000000000000L) represent the
 546:    * exponent, and bits 51-0 (masked by 0x000fffffffffffffL) are the mantissa.
 547:    * This function leaves NaN alone, so that you can recover the bit pattern
 548:    * with <code>Double.doubleToRawLongBits(double)</code>.
 549:    *
 550:    * @param bits the bits to convert
 551:    * @return the <code>double</code> represented by the bits
 552:    * @see #doubleToLongBits(double)
 553:    * @see #doubleToRawLongBits(double)
 554:    */
 555:   public static double longBitsToDouble(long bits)
 556:   {
 557:     return VMDouble.longBitsToDouble(bits);
 558:   }
 559: 
 560:   /**
 561:    * Compare two Doubles numerically by comparing their <code>double</code>
 562:    * values. The result is positive if the first is greater, negative if the
 563:    * second is greater, and 0 if the two are equal. However, this special
 564:    * cases NaN and signed zero as follows: NaN is considered greater than
 565:    * all other doubles, including <code>POSITIVE_INFINITY</code>, and positive
 566:    * zero is considered greater than negative zero.
 567:    *
 568:    * @param d the Double to compare
 569:    * @return the comparison
 570:    * @since 1.2
 571:    */
 572:   public int compareTo(Double d)
 573:   {
 574:     return compare(value, d.value);
 575:   }
 576: 
 577:   /**
 578:    * Behaves like <code>compareTo(Double)</code> unless the Object
 579:    * is not an <code>Double</code>.
 580:    *
 581:    * @param o the object to compare
 582:    * @return the comparison
 583:    * @throws ClassCastException if the argument is not a <code>Double</code>
 584:    * @see #compareTo(Double)
 585:    * @see Comparable
 586:    * @since 1.2
 587:    */
 588:   public int compareTo(Object o)
 589:   {
 590:     return compare(value, ((Double) o).value);
 591:   }
 592: 
 593:   /**
 594:    * Behaves like <code>new Double(x).compareTo(new Double(y))</code>; in
 595:    * other words this compares two doubles, special casing NaN and zero,
 596:    * without the overhead of objects.
 597:    *
 598:    * @param x the first double to compare
 599:    * @param y the second double to compare
 600:    * @return the comparison
 601:    * @since 1.4
 602:    */
 603:   public static int compare(double x, double y)
 604:   {
 605:     if (isNaN(x))
 606:       return isNaN(y) ? 0 : 1;
 607:     if (isNaN(y))
 608:       return -1;
 609:     // recall that 0.0 == -0.0, so we convert to infinites and try again
 610:     if (x == 0 && y == 0)
 611:       return (int) (1 / x - 1 / y);
 612:     if (x == y)
 613:       return 0;
 614: 
 615:     return x > y ? 1 : -1;
 616:   }
 617: }