libjava/java/lang/Double.java

   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., 59 Temple Place, Suite 330, Boston, MA
  20 02111-1307 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    * Load native routines necessary for this class.
 107    */
 108   static
 109   {
 110     if (Configuration.INIT_LOAD_LIBRARY)
 111       {
 112         System.loadLibrary("javalang");
 113         initIDs();
 114       }
 115   }
 116
 117   /**
 118    * Create a <code>Double</code> from the primitive <code>double</code>
 119    * specified.
 120    *
 121    * @param value the <code>double</code> argument
 122    */
 123   public Double(double value)
 124   {
 125     this.value = value;
 126   }
 127
 128   /**
 129    * Create a <code>Double</code> from the specified <code>String</code>.
 130    * This method calls <code>Double.parseDouble()</code>.
 131    *
 132    * @param s the <code>String</code> to convert
 133    * @throws NumberFormatException if <code>s</code> cannot be parsed as a
 134    *         <code>double</code>
 135    * @throws NullPointerException if <code>s</code> is null
 136    * @see #parseDouble(String)
 137    */
 138   public Double(String s)
 139   {
 140     value = parseDouble(s);
 141   }
 142
 143   /**
 144    * Convert the <code>double</code> to a <code>String</code>.
 145    * Floating-point string representation is fairly complex: here is a
 146    * rundown of the possible values.  "<code>[-]</code>" indicates that a
 147    * negative sign will be printed if the value (or exponent) is negative.
 148    * "<code>&lt;number&gt;</code>" means a string of digits ('0' to '9').
 149    * "<code>&lt;digit&gt;</code>" means a single digit ('0' to '9').<br>
 150    *
 151    * <table border=1>
 152    * <tr><th>Value of Double</th><th>String Representation</th></tr>
 153    * <tr><td>[+-] 0</td> <td><code>[-]0.0</code></td></tr>
 154    * <tr><td>Between [+-] 10<sup>-3</sup> and 10<sup>7</sup>, exclusive</td>
 155    *     <td><code>[-]number.number</code></td></tr>
 156    * <tr><td>Other numeric value</td>
 157    *     <td><code>[-]&lt;digit&gt;.&lt;number&gt;
 158    *          E[-]&lt;number&gt;</code></td></tr>
 159    * <tr><td>[+-] infinity</td> <td><code>[-]Infinity</code></td></tr>
 160    * <tr><td>NaN</td> <td><code>NaN</code></td></tr>
 161    * </table>
 162    *
 163    * Yes, negative zero <em>is</em> a possible value.  Note that there is
 164    * <em>always</em> a <code>.</code> and at least one digit printed after
 165    * it: even if the number is 3, it will be printed as <code>3.0</code>.
 166    * After the ".", all digits will be printed except trailing zeros. The
 167    * result is rounded to the shortest decimal number which will parse back
 168    * to the same double.
 169    *
 170    * <p>To create other output formats, use {@link java.text.NumberFormat}.
 171    *
 172    * @XXX specify where we are not in accord with the spec.
 173    *
 174    * @param d the <code>double</code> to convert
 175    * @return the <code>String</code> representing the <code>double</code>
 176    */
 177   public static String toString(double d)
 178   {
 179     return toString(d, false);
 180   }
 181
 182   /**
 183    * Create a new <code>Double</code> object using the <code>String</code>.
 184    *
 185    * @param s the <code>String</code> to convert
 186    * @return the new <code>Double</code>
 187    * @throws NumberFormatException if <code>s</code> cannot be parsed as a
 188    *         <code>double</code>
 189    * @throws NullPointerException if <code>s</code> is null.
 190    * @see #parseDouble(String)
 191    */
 192   public static Double valueOf(String s)
 193   {
 194     return new Double(parseDouble(s));
 195   }
 196
 197   /**
 198    * Parse the specified <code>String</code> as a <code>double</code>. The
 199    * extended BNF grammar is as follows:<br>
 200    * <pre>
 201    * <em>DecodableString</em>:
 202    *      ( [ <code>-</code> | <code>+</code> ] <code>NaN</code> )
 203    *    | ( [ <code>-</code> | <code>+</code> ] <code>Infinity</code> )
 204    *    | ( [ <code>-</code> | <code>+</code> ] <em>FloatingPoint</em>
 205    *              [ <code>f</code> | <code>F</code> | <code>d</code>
 206    *                | <code>D</code>] )
 207    * <em>FloatingPoint</em>:
 208    *      ( { <em>Digit</em> }+ [ <code>.</code> { <em>Digit</em> } ]
 209    *              [ <em>Exponent</em> ] )
 210    *    | ( <code>.</code> { <em>Digit</em> }+ [ <em>Exponent</em> ] )
 211    * <em>Exponent</em>:
 212    *      ( ( <code>e</code> | <code>E</code> )
 213    *              [ <code>-</code> | <code>+</code> ] { <em>Digit</em> }+ )
 214    * <em>Digit</em>: <em><code>'0'</code> through <code>'9'</code></em>
 215    * </pre>
 216    *
 217    * <p>NaN and infinity are special cases, to allow parsing of the output
 218    * of toString.  Otherwise, the result is determined by calculating
 219    * <em>n * 10<sup>exponent</sup></em> to infinite precision, then rounding
 220    * to the nearest double. Remember that many numbers cannot be precisely
 221    * represented in floating point. In case of overflow, infinity is used,
 222    * and in case of underflow, signed zero is used. Unlike Integer.parseInt,
 223    * this does not accept Unicode digits outside the ASCII range.
 224    *
 225    * <p>If an unexpected character is found in the <code>String</code>, a
 226    * <code>NumberFormatException</code> will be thrown.  Leading and trailing
 227    * 'whitespace' is ignored via <code>String.trim()</code>, but spaces
 228    * internal to the actual number are not allowed.
 229    *
 230    * <p>To parse numbers according to another format, consider using
 231    * {@link java.text.NumberFormat}.
 232    *
 233    * @XXX specify where/how we are not in accord with the spec.
 234    *
 235    * @param str the <code>String</code> to convert
 236    * @return the <code>double</code> value of <code>s</code>
 237    * @throws NumberFormatException if <code>s</code> cannot be parsed as a
 238    *         <code>double</code>
 239    * @throws NullPointerException if <code>s</code> is null
 240    * @see #MIN_VALUE
 241    * @see #MAX_VALUE
 242    * @see #POSITIVE_INFINITY
 243    * @see #NEGATIVE_INFINITY
 244    * @since 1.2
 245    */
 246   public static native double parseDouble(String str);
 247
 248   /**
 249    * Return <code>true</code> if the <code>double</code> has the same
 250    * value as <code>NaN</code>, otherwise return <code>false</code>.
 251    *
 252    * @param v the <code>double</code> to compare
 253    * @return whether the argument is <code>NaN</code>.
 254    */
 255   public static boolean isNaN(double v)
 256   {
 257     // This works since NaN != NaN is the only reflexive inequality
 258     // comparison which returns true.
 259     return v != v;
 260   }
 261
 262   /**
 263    * Return <code>true</code> if the <code>double</code> has a value
 264    * equal to either <code>NEGATIVE_INFINITY</code> or
 265    * <code>POSITIVE_INFINITY</code>, otherwise return <code>false</code>.
 266    *
 267    * @param v the <code>double</code> to compare
 268    * @return whether the argument is (-/+) infinity.
 269    */
 270   public static boolean isInfinite(double v)
 271   {
 272     return v == POSITIVE_INFINITY || v == NEGATIVE_INFINITY;
 273   }
 274
 275   /**
 276    * Return <code>true</code> if the value of this <code>Double</code>
 277    * is the same as <code>NaN</code>, otherwise return <code>false</code>.
 278    *
 279    * @return whether this <code>Double</code> is <code>NaN</code>
 280    */
 281   public boolean isNaN()
 282   {
 283     return isNaN(value);
 284   }
 285
 286   /**
 287    * Return <code>true</code> if the value of this <code>Double</code>
 288    * is the same as <code>NEGATIVE_INFINITY</code> or
 289    * <code>POSITIVE_INFINITY</code>, otherwise return <code>false</code>.
 290    *
 291    * @return whether this <code>Double</code> is (-/+) infinity
 292    */
 293   public boolean isInfinite()
 294   {
 295     return isInfinite(value);
 296   }
 297
 298   /**
 299    * Convert the <code>double</code> value of this <code>Double</code>
 300    * to a <code>String</code>.  This method calls
 301    * <code>Double.toString(double)</code> to do its dirty work.
 302    *
 303    * @return the <code>String</code> representation
 304    * @see #toString(double)
 305    */
 306   public String toString()
 307   {
 308     return toString(value);
 309   }
 310
 311   /**
 312    * Return the value of this <code>Double</code> as a <code>byte</code>.
 313    *
 314    * @return the byte value
 315    * @since 1.1
 316    */
 317   public byte byteValue()
 318   {
 319     return (byte) value;
 320   }
 321
 322   /**
 323    * Return the value of this <code>Double</code> as a <code>short</code>.
 324    *
 325    * @return the short value
 326    * @since 1.1
 327    */
 328   public short shortValue()
 329   {
 330     return (short) value;
 331   }
 332
 333   /**
 334    * Return the value of this <code>Double</code> as an <code>int</code>.
 335    *
 336    * @return the int value
 337    */
 338   public int intValue()
 339   {
 340     return (int) value;
 341   }
 342
 343   /**
 344    * Return the value of this <code>Double</code> as a <code>long</code>.
 345    *
 346    * @return the long value
 347    */
 348   public long longValue()
 349   {
 350     return (long) value;
 351   }
 352
 353   /**
 354    * Return the value of this <code>Double</code> as a <code>float</code>.
 355    *
 356    * @return the float value
 357    */
 358   public float floatValue()
 359   {
 360     return (float) value;
 361   }
 362
 363   /**
 364    * Return the value of this <code>Double</code>.
 365    *
 366    * @return the double value
 367    */
 368   public double doubleValue()
 369   {
 370     return value;
 371   }
 372
 373   /**
 374    * Return a hashcode representing this Object. <code>Double</code>'s hash
 375    * code is calculated by:<br>
 376    * <code>long v = Double.doubleToLongBits(doubleValue());<br>
 377    *    int hash = (int)(v^(v&gt;&gt;32))</code>.
 378    *
 379    * @return this Object's hash code
 380    * @see #doubleToLongBits(double)
 381    */
 382   public int hashCode()
 383   {
 384     long v = doubleToLongBits(value);
 385     return (int) (v ^ (v >>> 32));
 386   }
 387
 388   /**
 389    * Returns <code>true</code> if <code>obj</code> is an instance of
 390    * <code>Double</code> and represents the same double value. Unlike comparing
 391    * two doubles with <code>==</code>, this treats two instances of
 392    * <code>Double.NaN</code> as equal, but treats <code>0.0</code> and
 393    * <code>-0.0</code> as unequal.
 394    *
 395    * <p>Note that <code>d1.equals(d2)</code> is identical to
 396    * <code>doubleToLongBits(d1.doubleValue()) ==
 397    *    doubleToLongBits(d2.doubleValue())</code>.
 398    *
 399    * @param obj the object to compare
 400    * @return whether the objects are semantically equal
 401    */
 402   public boolean equals(Object obj)
 403   {
 404     if (! (obj instanceof Double))
 405       return false;
 406
 407     double d = ((Double) obj).value;
 408
 409     // Avoid call to native method. However, some implementations, like gcj,
 410     // are better off using floatToIntBits(value) == floatToIntBits(f).
 411     // Check common case first, then check NaN and 0.
 412     if (value == d)
 413       return (value != 0) || (1 / value == 1 / d);
 414     return isNaN(value) && isNaN(d);
 415   }
 416
 417   /**
 418    * Convert the double to the IEEE 754 floating-point "double format" bit
 419    * layout. Bit 63 (the most significant) is the sign bit, bits 62-52
 420    * (masked by 0x7ff0000000000000L) represent the exponent, and bits 51-0
 421    * (masked by 0x000fffffffffffffL) are the mantissa. This function
 422    * collapses all versions of NaN to 0x7ff8000000000000L. The result of this
 423    * function can be used as the argument to
 424    * <code>Double.longBitsToDouble(long)</code> to obtain the original
 425    * <code>double</code> value.
 426    *
 427    * @param value the <code>double</code> to convert
 428    * @return the bits of the <code>double</code>
 429    * @see #longBitsToDouble(long)
 430    */
 431   // GCJ LOCAL: We diverge from Classpath for efficiency.
 432   public static native long doubleToLongBits(double value);
 433   // END GCJ LOCAL
 434
 435   /**
 436    * Convert the double to the IEEE 754 floating-point "double format" bit
 437    * layout. Bit 63 (the most significant) is the sign bit, bits 62-52
 438    * (masked by 0x7ff0000000000000L) represent the exponent, and bits 51-0
 439    * (masked by 0x000fffffffffffffL) are the mantissa. This function
 440    * leaves NaN alone, rather than collapsing to a canonical value. The
 441    * result of this function can be used as the argument to
 442    * <code>Double.longBitsToDouble(long)</code> to obtain the original
 443    * <code>double</code> value.
 444    *
 445    * @param value the <code>double</code> to convert
 446    * @return the bits of the <code>double</code>
 447    * @see #longBitsToDouble(long)
 448    */
 449   // GCJ LOCAL: We diverge from Classpath for efficiency.
 450   public static native long doubleToRawLongBits(double value);
 451   // END GCJ LOCAL
 452
 453   /**
 454    * Convert the argument in IEEE 754 floating-point "double format" bit
 455    * layout to the corresponding float. Bit 63 (the most significant) is the
 456    * sign bit, bits 62-52 (masked by 0x7ff0000000000000L) represent the
 457    * exponent, and bits 51-0 (masked by 0x000fffffffffffffL) are the mantissa.
 458    * This function leaves NaN alone, so that you can recover the bit pattern
 459    * with <code>Double.doubleToRawLongBits(double)</code>.
 460    *
 461    * @param bits the bits to convert
 462    * @return the <code>double</code> represented by the bits
 463    * @see #doubleToLongBits(double)
 464    * @see #doubleToRawLongBits(double)
 465    */
 466   // GCJ LOCAL: We diverge from Classpath for efficiency.
 467   public static native double longBitsToDouble(long bits);
 468   // END GCJ LOCAL
 469
 470   /**
 471    * Compare two Doubles numerically by comparing their <code>double</code>
 472    * values. The result is positive if the first is greater, negative if the
 473    * second is greater, and 0 if the two are equal. However, this special
 474    * cases NaN and signed zero as follows: NaN is considered greater than
 475    * all other doubles, including <code>POSITIVE_INFINITY</code>, and positive
 476    * zero is considered greater than negative zero.
 477    *
 478    * @param d the Double to compare
 479    * @return the comparison
 480    * @since 1.2
 481    */
 482   public int compareTo(Double d)
 483   {
 484     return compare(value, d.value);
 485   }
 486
 487   /**
 488    * Behaves like <code>compareTo(Double)</code> unless the Object
 489    * is not an <code>Double</code>.
 490    *
 491    * @param o the object to compare
 492    * @return the comparison
 493    * @throws ClassCastException if the argument is not a <code>Double</code>
 494    * @see #compareTo(Double)
 495    * @see Comparable
 496    * @since 1.2
 497    */
 498   public int compareTo(Object o)
 499   {
 500     return compare(value, ((Double) o).value);
 501   }
 502
 503   /**
 504    * Behaves like <code>new Double(x).compareTo(new Double(y))</code>; in
 505    * other words this compares two doubles, special casing NaN and zero,
 506    * without the overhead of objects.
 507    *
 508    * @param x the first double to compare
 509    * @param y the second double to compare
 510    * @return the comparison
 511    * @since 1.4
 512    */
 513   public static int compare(double x, double y)
 514   {
 515     if (isNaN(x))
 516       return isNaN(y) ? 0 : 1;
 517     if (isNaN(y))
 518       return -1;
 519     // recall that 0.0 == -0.0, so we convert to infinites and try again
 520     if (x == 0 && y == 0)
 521       return (int) (1 / x - 1 / y);
 522     if (x == y)
 523       return 0;
 524
 525     return x > y ? 1 : -1;
 526   }
 527
 528   /**
 529    * Helper method to convert to string.
 530    *
 531    * @param d the double to convert
 532    * @param isFloat true if the conversion is requested by Float (results in
 533    *        fewer digits)
 534    */
 535   // Package visible for use by Float.
 536   static native String toString(double d, boolean isFloat);
 537
 538   /**
 539    * Initialize JNI cache.  This method is called only by the
 540    * static initializer when using JNI.
 541    */
 542   private static native void initIDs();
 543 }