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:    * Returns a <code>Double</code> object wrapping the value.
 177:    * In contrast to the <code>Double</code> constructor, this method
 178:    * may cache some values.  It is used by boxing conversion.
 179:    *
 180:    * @param val the value to wrap
 181:    * @return the <code>Double</code>
 182:    * 
 183:    * @since 1.5
 184:    */
 185:   public static Double valueOf(double val)
 186:   {
 187:     // We don't actually cache, but we could.
 188:     return new Double(val);
 189:   }
 190: 
 191:  /**
 192:    * Create a new <code>Double</code> object using the <code>String</code>.
 193:    *
 194:    * @param s the <code>String</code> to convert
 195:    * @return the new <code>Double</code>
 196:    * @throws NumberFormatException if <code>s</code> cannot be parsed as a
 197:    *         <code>double</code>
 198:    * @throws NullPointerException if <code>s</code> is null.
 199:    * @see #parseDouble(String)
 200:    */
 201:   public static Double valueOf(String s)
 202:   {
 203:     return new Double(parseDouble(s));
 204:   }
 205: 
 206:   /**
 207:    * Parse the specified <code>String</code> as a <code>double</code>. The
 208:    * extended BNF grammar is as follows:<br>
 209:    * <pre>
 210:    * <em>DecodableString</em>:
 211:    *      ( [ <code>-</code> | <code>+</code> ] <code>NaN</code> )
 212:    *    | ( [ <code>-</code> | <code>+</code> ] <code>Infinity</code> )
 213:    *    | ( [ <code>-</code> | <code>+</code> ] <em>FloatingPoint</em>
 214:    *              [ <code>f</code> | <code>F</code> | <code>d</code>
 215:    *                | <code>D</code>] )
 216:    * <em>FloatingPoint</em>:
 217:    *      ( { <em>Digit</em> }+ [ <code>.</code> { <em>Digit</em> } ]
 218:    *              [ <em>Exponent</em> ] )
 219:    *    | ( <code>.</code> { <em>Digit</em> }+ [ <em>Exponent</em> ] )
 220:    * <em>Exponent</em>:
 221:    *      ( ( <code>e</code> | <code>E</code> )
 222:    *              [ <code>-</code> | <code>+</code> ] { <em>Digit</em> }+ )
 223:    * <em>Digit</em>: <em><code>'0'</code> through <code>'9'</code></em>
 224:    * </pre>
 225:    *
 226:    * <p>NaN and infinity are special cases, to allow parsing of the output
 227:    * of toString.  Otherwise, the result is determined by calculating
 228:    * <em>n * 10<sup>exponent</sup></em> to infinite precision, then rounding
 229:    * to the nearest double. Remember that many numbers cannot be precisely
 230:    * represented in floating point. In case of overflow, infinity is used,
 231:    * and in case of underflow, signed zero is used. Unlike Integer.parseInt,
 232:    * this does not accept Unicode digits outside the ASCII range.
 233:    *
 234:    * <p>If an unexpected character is found in the <code>String</code>, a
 235:    * <code>NumberFormatException</code> will be thrown.  Leading and trailing
 236:    * 'whitespace' is ignored via <code>String.trim()</code>, but spaces
 237:    * internal to the actual number are not allowed.
 238:    *
 239:    * <p>To parse numbers according to another format, consider using
 240:    * {@link java.text.NumberFormat}.
 241:    *
 242:    * @XXX specify where/how we are not in accord with the spec.
 243:    *
 244:    * @param str the <code>String</code> to convert
 245:    * @return the <code>double</code> value of <code>s</code>
 246:    * @throws NumberFormatException if <code>s</code> cannot be parsed as a
 247:    *         <code>double</code>
 248:    * @throws NullPointerException if <code>s</code> is null
 249:    * @see #MIN_VALUE
 250:    * @see #MAX_VALUE
 251:    * @see #POSITIVE_INFINITY
 252:    * @see #NEGATIVE_INFINITY
 253:    * @since 1.2
 254:    */
 255:   public static double parseDouble(String str)
 256:   {
 257:     return VMDouble.parseDouble(str);
 258:   }
 259: 
 260:   /**
 261:    * Return <code>true</code> if the <code>double</code> has the same
 262:    * value as <code>NaN</code>, otherwise return <code>false</code>.
 263:    *
 264:    * @param v the <code>double</code> to compare
 265:    * @return whether the argument is <code>NaN</code>.
 266:    */
 267:   public static boolean isNaN(double v)
 268:   {
 269:     // This works since NaN != NaN is the only reflexive inequality
 270:     // comparison which returns true.
 271:     return v != v;
 272:   }
 273: 
 274:   /**
 275:    * Return <code>true</code> if the <code>double</code> has a value
 276:    * equal to either <code>NEGATIVE_INFINITY</code> or
 277:    * <code>POSITIVE_INFINITY</code>, otherwise return <code>false</code>.
 278:    *
 279:    * @param v the <code>double</code> to compare
 280:    * @return whether the argument is (-/+) infinity.
 281:    */
 282:   public static boolean isInfinite(double v)
 283:   {
 284:     return v == POSITIVE_INFINITY || v == NEGATIVE_INFINITY;
 285:   }
 286: 
 287:   /**
 288:    * Return <code>true</code> if the value of this <code>Double</code>
 289:    * is the same as <code>NaN</code>, otherwise return <code>false</code>.
 290:    *
 291:    * @return whether this <code>Double</code> is <code>NaN</code>
 292:    */
 293:   public boolean isNaN()
 294:   {
 295:     return isNaN(value);
 296:   }
 297: 
 298:   /**
 299:    * Return <code>true</code> if the value of this <code>Double</code>
 300:    * is the same as <code>NEGATIVE_INFINITY</code> or
 301:    * <code>POSITIVE_INFINITY</code>, otherwise return <code>false</code>.
 302:    *
 303:    * @return whether this <code>Double</code> is (-/+) infinity
 304:    */
 305:   public boolean isInfinite()
 306:   {
 307:     return isInfinite(value);
 308:   }
 309: 
 310:   /**
 311:    * Convert the <code>double</code> value of this <code>Double</code>
 312:    * to a <code>String</code>.  This method calls
 313:    * <code>Double.toString(double)</code> to do its dirty work.
 314:    *
 315:    * @return the <code>String</code> representation
 316:    * @see #toString(double)
 317:    */
 318:   public String toString()
 319:   {
 320:     return toString(value);
 321:   }
 322: 
 323:   /**
 324:    * Return the value of this <code>Double</code> as a <code>byte</code>.
 325:    *
 326:    * @return the byte value
 327:    * @since 1.1
 328:    */
 329:   public byte byteValue()
 330:   {
 331:     return (byte) value;
 332:   }
 333: 
 334:   /**
 335:    * Return the value of this <code>Double</code> as a <code>short</code>.
 336:    *
 337:    * @return the short value
 338:    * @since 1.1
 339:    */
 340:   public short shortValue()
 341:   {
 342:     return (short) value;
 343:   }
 344: 
 345:   /**
 346:    * Return the value of this <code>Double</code> as an <code>int</code>.
 347:    *
 348:    * @return the int value
 349:    */
 350:   public int intValue()
 351:   {
 352:     return (int) value;
 353:   }
 354: 
 355:   /**
 356:    * Return the value of this <code>Double</code> as a <code>long</code>.
 357:    *
 358:    * @return the long value
 359:    */
 360:   public long longValue()
 361:   {
 362:     return (long) value;
 363:   }
 364: 
 365:   /**
 366:    * Return the value of this <code>Double</code> as a <code>float</code>.
 367:    *
 368:    * @return the float value
 369:    */
 370:   public float floatValue()
 371:   {
 372:     return (float) value;
 373:   }
 374: 
 375:   /**
 376:    * Return the value of this <code>Double</code>.
 377:    *
 378:    * @return the double value
 379:    */
 380:   public double doubleValue()
 381:   {
 382:     return value;
 383:   }
 384: 
 385:   /**
 386:    * Return a hashcode representing this Object. <code>Double</code>'s hash
 387:    * code is calculated by:<br>
 388:    * <code>long v = Double.doubleToLongBits(doubleValue());<br>
 389:    *    int hash = (int)(v^(v&gt;&gt;32))</code>.
 390:    *
 391:    * @return this Object's hash code
 392:    * @see #doubleToLongBits(double)
 393:    */
 394:   public int hashCode()
 395:   {
 396:     long v = doubleToLongBits(value);
 397:     return (int) (v ^ (v >>> 32));
 398:   }
 399: 
 400:   /**
 401:    * Returns <code>true</code> if <code>obj</code> is an instance of
 402:    * <code>Double</code> and represents the same double value. Unlike comparing
 403:    * two doubles with <code>==</code>, this treats two instances of
 404:    * <code>Double.NaN</code> as equal, but treats <code>0.0</code> and
 405:    * <code>-0.0</code> as unequal.
 406:    *
 407:    * <p>Note that <code>d1.equals(d2)</code> is identical to
 408:    * <code>doubleToLongBits(d1.doubleValue()) ==
 409:    *    doubleToLongBits(d2.doubleValue())</code>.
 410:    *
 411:    * @param obj the object to compare
 412:    * @return whether the objects are semantically equal
 413:    */
 414:   public boolean equals(Object obj)
 415:   {
 416:     if (! (obj instanceof Double))
 417:       return false;
 418: 
 419:     double d = ((Double) obj).value;
 420: 
 421:     // Avoid call to native method. However, some implementations, like gcj,
 422:     // are better off using floatToIntBits(value) == floatToIntBits(f).
 423:     // Check common case first, then check NaN and 0.
 424:     if (value == d)
 425:       return (value != 0) || (1 / value == 1 / d);
 426:     return isNaN(value) && isNaN(d);
 427:   }
 428: 
 429:   /**
 430:    * Convert the double to the IEEE 754 floating-point "double format" bit
 431:    * layout. Bit 63 (the most significant) is the sign bit, bits 62-52
 432:    * (masked by 0x7ff0000000000000L) represent the exponent, and bits 51-0
 433:    * (masked by 0x000fffffffffffffL) are the mantissa. This function
 434:    * collapses all versions of NaN to 0x7ff8000000000000L. The result of this
 435:    * function can be used as the argument to
 436:    * <code>Double.longBitsToDouble(long)</code> to obtain the original
 437:    * <code>double</code> value.
 438:    *
 439:    * @param value the <code>double</code> to convert
 440:    * @return the bits of the <code>double</code>
 441:    * @see #longBitsToDouble(long)
 442:    */
 443:   public static long doubleToLongBits(double value)
 444:   {
 445:     return VMDouble.doubleToLongBits(value);
 446:   }
 447: 
 448:   /**
 449:    * Convert the double to the IEEE 754 floating-point "double format" bit
 450:    * layout. Bit 63 (the most significant) is the sign bit, bits 62-52
 451:    * (masked by 0x7ff0000000000000L) represent the exponent, and bits 51-0
 452:    * (masked by 0x000fffffffffffffL) are the mantissa. This function
 453:    * leaves NaN alone, rather than collapsing to a canonical value. The
 454:    * result of this function can be used as the argument to
 455:    * <code>Double.longBitsToDouble(long)</code> to obtain the original
 456:    * <code>double</code> value.
 457:    *
 458:    * @param value the <code>double</code> to convert
 459:    * @return the bits of the <code>double</code>
 460:    * @see #longBitsToDouble(long)
 461:    */
 462:   public static long doubleToRawLongBits(double value)
 463:   {
 464:     return VMDouble.doubleToRawLongBits(value);
 465:   }
 466: 
 467:   /**
 468:    * Convert the argument in IEEE 754 floating-point "double format" bit
 469:    * layout to the corresponding float. Bit 63 (the most significant) is the
 470:    * sign bit, bits 62-52 (masked by 0x7ff0000000000000L) represent the
 471:    * exponent, and bits 51-0 (masked by 0x000fffffffffffffL) are the mantissa.
 472:    * This function leaves NaN alone, so that you can recover the bit pattern
 473:    * with <code>Double.doubleToRawLongBits(double)</code>.
 474:    *
 475:    * @param bits the bits to convert
 476:    * @return the <code>double</code> represented by the bits
 477:    * @see #doubleToLongBits(double)
 478:    * @see #doubleToRawLongBits(double)
 479:    */
 480:   public static double longBitsToDouble(long bits)
 481:   {
 482:     return VMDouble.longBitsToDouble(bits);
 483:   }
 484: 
 485:   /**
 486:    * Compare two Doubles numerically by comparing their <code>double</code>
 487:    * values. The result is positive if the first is greater, negative if the
 488:    * second is greater, and 0 if the two are equal. However, this special
 489:    * cases NaN and signed zero as follows: NaN is considered greater than
 490:    * all other doubles, including <code>POSITIVE_INFINITY</code>, and positive
 491:    * zero is considered greater than negative zero.
 492:    *
 493:    * @param d the Double to compare
 494:    * @return the comparison
 495:    * @since 1.2
 496:    */
 497:   public int compareTo(Double d)
 498:   {
 499:     return compare(value, d.value);
 500:   }
 501: 
 502:   /**
 503:    * Behaves like <code>compareTo(Double)</code> unless the Object
 504:    * is not an <code>Double</code>.
 505:    *
 506:    * @param o the object to compare
 507:    * @return the comparison
 508:    * @throws ClassCastException if the argument is not a <code>Double</code>
 509:    * @see #compareTo(Double)
 510:    * @see Comparable
 511:    * @since 1.2
 512:    */
 513:   public int compareTo(Object o)
 514:   {
 515:     return compare(value, ((Double) o).value);
 516:   }
 517: 
 518:   /**
 519:    * Behaves like <code>new Double(x).compareTo(new Double(y))</code>; in
 520:    * other words this compares two doubles, special casing NaN and zero,
 521:    * without the overhead of objects.
 522:    *
 523:    * @param x the first double to compare
 524:    * @param y the second double to compare
 525:    * @return the comparison
 526:    * @since 1.4
 527:    */
 528:   public static int compare(double x, double y)
 529:   {
 530:     if (isNaN(x))
 531:       return isNaN(y) ? 0 : 1;
 532:     if (isNaN(y))
 533:       return -1;
 534:     // recall that 0.0 == -0.0, so we convert to infinites and try again
 535:     if (x == 0 && y == 0)
 536:       return (int) (1 / x - 1 / y);
 537:     if (x == y)
 538:       return 0;
 539: 
 540:     return x > y ? 1 : -1;
 541:   }
 542: }