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