libjava/java/lang/Double.java

   1 /* Double.java -- object wrapper for double
   2    Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2005, 2006
   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 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 native double parseDouble(String str);
 256
 257   /**
 258    * Return <code>true</code> if the <code>double</code> has the same
 259    * value as <code>NaN</code>, otherwise return <code>false</code>.
 260    *
 261    * @param v the <code>double</code> to compare
 262    * @return whether the argument is <code>NaN</code>.
 263    */
 264   public static boolean isNaN(double v)
 265   {
 266     // This works since NaN != NaN is the only reflexive inequality
 267     // comparison which returns true.
 268     return v != v;
 269   }
 270
 271   /**
 272    * Return <code>true</code> if the <code>double</code> has a value
 273    * equal to either <code>NEGATIVE_INFINITY</code> or
 274    * <code>POSITIVE_INFINITY</code>, otherwise return <code>false</code>.
 275    *
 276    * @param v the <code>double</code> to compare
 277    * @return whether the argument is (-/+) infinity.
 278    */
 279   public static boolean isInfinite(double v)
 280   {
 281     return v == POSITIVE_INFINITY || v == NEGATIVE_INFINITY;
 282   }
 283
 284   /**
 285    * Return <code>true</code> if the value of this <code>Double</code>
 286    * is the same as <code>NaN</code>, otherwise return <code>false</code>.
 287    *
 288    * @return whether this <code>Double</code> is <code>NaN</code>
 289    */
 290   public boolean isNaN()
 291   {
 292     return isNaN(value);
 293   }
 294
 295   /**
 296    * Return <code>true</code> if the value of this <code>Double</code>
 297    * is the same as <code>NEGATIVE_INFINITY</code> or
 298    * <code>POSITIVE_INFINITY</code>, otherwise return <code>false</code>.
 299    *
 300    * @return whether this <code>Double</code> is (-/+) infinity
 301    */
 302   public boolean isInfinite()
 303   {
 304     return isInfinite(value);
 305   }
 306
 307   /**
 308    * Convert the <code>double</code> value of this <code>Double</code>
 309    * to a <code>String</code>.  This method calls
 310    * <code>Double.toString(double)</code> to do its dirty work.
 311    *
 312    * @return the <code>String</code> representation
 313    * @see #toString(double)
 314    */
 315   public String toString()
 316   {
 317     return toString(value);
 318   }
 319
 320   /**
 321    * Return the value of this <code>Double</code> as a <code>byte</code>.
 322    *
 323    * @return the byte value
 324    * @since 1.1
 325    */
 326   public byte byteValue()
 327   {
 328     return (byte) value;
 329   }
 330
 331   /**
 332    * Return the value of this <code>Double</code> as a <code>short</code>.
 333    *
 334    * @return the short value
 335    * @since 1.1
 336    */
 337   public short shortValue()
 338   {
 339     return (short) value;
 340   }
 341
 342   /**
 343    * Return the value of this <code>Double</code> as an <code>int</code>.
 344    *
 345    * @return the int value
 346    */
 347   public int intValue()
 348   {
 349     return (int) value;
 350   }
 351
 352   /**
 353    * Return the value of this <code>Double</code> as a <code>long</code>.
 354    *
 355    * @return the long value
 356    */
 357   public long longValue()
 358   {
 359     return (long) value;
 360   }
 361
 362   /**
 363    * Return the value of this <code>Double</code> as a <code>float</code>.
 364    *
 365    * @return the float value
 366    */
 367   public float floatValue()
 368   {
 369     return (float) value;
 370   }
 371
 372   /**
 373    * Return the value of this <code>Double</code>.
 374    *
 375    * @return the double value
 376    */
 377   public double doubleValue()
 378   {
 379     return value;
 380   }
 381
 382   /**
 383    * Return a hashcode representing this Object. <code>Double</code>'s hash
 384    * code is calculated by:<br>
 385    * <code>long v = Double.doubleToLongBits(doubleValue());<br>
 386    *    int hash = (int)(v^(v&gt;&gt;32))</code>.
 387    *
 388    * @return this Object's hash code
 389    * @see #doubleToLongBits(double)
 390    */
 391   public int hashCode()
 392   {
 393     long v = doubleToLongBits(value);
 394     return (int) (v ^ (v >>> 32));
 395   }
 396
 397   /**
 398    * Returns <code>true</code> if <code>obj</code> is an instance of
 399    * <code>Double</code> and represents the same double value. Unlike comparing
 400    * two doubles with <code>==</code>, this treats two instances of
 401    * <code>Double.NaN</code> as equal, but treats <code>0.0</code> and
 402    * <code>-0.0</code> as unequal.
 403    *
 404    * <p>Note that <code>d1.equals(d2)</code> is identical to
 405    * <code>doubleToLongBits(d1.doubleValue()) ==
 406    *    doubleToLongBits(d2.doubleValue())</code>.
 407    *
 408    * @param obj the object to compare
 409    * @return whether the objects are semantically equal
 410    */
 411   public boolean equals(Object obj)
 412   {
 413     if (! (obj instanceof Double))
 414       return false;
 415
 416     double d = ((Double) obj).value;
 417
 418     // Avoid call to native method. However, some implementations, like gcj,
 419     // are better off using floatToIntBits(value) == floatToIntBits(f).
 420     // Check common case first, then check NaN and 0.
 421     if (value == d)
 422       return (value != 0) || (1 / value == 1 / d);
 423     return isNaN(value) && isNaN(d);
 424   }
 425
 426   /**
 427    * Convert the double to the IEEE 754 floating-point "double format" bit
 428    * layout. Bit 63 (the most significant) is the sign bit, bits 62-52
 429    * (masked by 0x7ff0000000000000L) represent the exponent, and bits 51-0
 430    * (masked by 0x000fffffffffffffL) are the mantissa. This function
 431    * collapses all versions of NaN to 0x7ff8000000000000L. The result of this
 432    * function can be used as the argument to
 433    * <code>Double.longBitsToDouble(long)</code> to obtain the original
 434    * <code>double</code> value.
 435    *
 436    * @param value the <code>double</code> to convert
 437    * @return the bits of the <code>double</code>
 438    * @see #longBitsToDouble(long)
 439    */
 440   // GCJ LOCAL: We diverge from Classpath for efficiency.
 441   public static native long doubleToLongBits(double value);
 442   // END GCJ LOCAL
 443
 444   /**
 445    * Convert the double to the IEEE 754 floating-point "double format" bit
 446    * layout. Bit 63 (the most significant) is the sign bit, bits 62-52
 447    * (masked by 0x7ff0000000000000L) represent the exponent, and bits 51-0
 448    * (masked by 0x000fffffffffffffL) are the mantissa. This function
 449    * leaves NaN alone, rather than collapsing to a canonical value. The
 450    * result of this function can be used as the argument to
 451    * <code>Double.longBitsToDouble(long)</code> to obtain the original
 452    * <code>double</code> value.
 453    *
 454    * @param value the <code>double</code> to convert
 455    * @return the bits of the <code>double</code>
 456    * @see #longBitsToDouble(long)
 457    */
 458   // GCJ LOCAL: We diverge from Classpath for efficiency.
 459   public static native long doubleToRawLongBits(double value);
 460   // END GCJ LOCAL
 461
 462   /**
 463    * Convert the argument in IEEE 754 floating-point "double format" bit
 464    * layout to the corresponding float. Bit 63 (the most significant) is the
 465    * sign bit, bits 62-52 (masked by 0x7ff0000000000000L) represent the
 466    * exponent, and bits 51-0 (masked by 0x000fffffffffffffL) are the mantissa.
 467    * This function leaves NaN alone, so that you can recover the bit pattern
 468    * with <code>Double.doubleToRawLongBits(double)</code>.
 469    *
 470    * @param bits the bits to convert
 471    * @return the <code>double</code> represented by the bits
 472    * @see #doubleToLongBits(double)
 473    * @see #doubleToRawLongBits(double)
 474    */
 475   // GCJ LOCAL: We diverge from Classpath for efficiency.
 476   public static native double longBitsToDouble(long bits);
 477   // END GCJ LOCAL
 478
 479   /**
 480    * Compare two Doubles numerically by comparing their <code>double</code>
 481    * values. The result is positive if the first is greater, negative if the
 482    * second is greater, and 0 if the two are equal. However, this special
 483    * cases NaN and signed zero as follows: NaN is considered greater than
 484    * all other doubles, including <code>POSITIVE_INFINITY</code>, and positive
 485    * zero is considered greater than negative zero.
 486    *
 487    * @param d the Double to compare
 488    * @return the comparison
 489    * @since 1.2
 490    */
 491   public int compareTo(Double d)
 492   {
 493     return compare(value, d.value);
 494   }
 495
 496   /**
 497    * Behaves like <code>compareTo(Double)</code> unless the Object
 498    * is not an <code>Double</code>.
 499    *
 500    * @param o the object to compare
 501    * @return the comparison
 502    * @throws ClassCastException if the argument is not a <code>Double</code>
 503    * @see #compareTo(Double)
 504    * @see Comparable
 505    * @since 1.2
 506    */
 507   public int compareTo(Object o)
 508   {
 509     return compare(value, ((Double) o).value);
 510   }
 511
 512   /**
 513    * Behaves like <code>new Double(x).compareTo(new Double(y))</code>; in
 514    * other words this compares two doubles, special casing NaN and zero,
 515    * without the overhead of objects.
 516    *
 517    * @param x the first double to compare
 518    * @param y the second double to compare
 519    * @return the comparison
 520    * @since 1.4
 521    */
 522   public static int compare(double x, double y)
 523   {
 524     if (isNaN(x))
 525       return isNaN(y) ? 0 : 1;
 526     if (isNaN(y))
 527       return -1;
 528     // recall that 0.0 == -0.0, so we convert to infinites and try again
 529     if (x == 0 && y == 0)
 530       return (int) (1 / x - 1 / y);
 531     if (x == y)
 532       return 0;
 533
 534     return x > y ? 1 : -1;
 535   }
 536
 537   /**
 538    * Helper method to convert to string.
 539    *
 540    * @param d the double to convert
 541    * @param isFloat true if the conversion is requested by Float (results in
 542    *        fewer digits)
 543    */
 544   // Package visible for use by Float.
 545   static native String toString(double d, boolean isFloat);
 546 }