001    /* Double.java -- object wrapper for double
002       Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
003       Free Software Foundation, Inc.
004    
005    This file is part of GNU Classpath.
006    
007    GNU Classpath is free software; you can redistribute it and/or modify
008    it under the terms of the GNU General Public License as published by
009    the Free Software Foundation; either version 2, or (at your option)
010    any later version.
011    
012    GNU Classpath is distributed in the hope that it will be useful, but
013    WITHOUT ANY WARRANTY; without even the implied warranty of
014    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
015    General Public License for more details.
016    
017    You should have received a copy of the GNU General Public License
018    along with GNU Classpath; see the file COPYING.  If not, write to the
019    Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
020    02110-1301 USA.
021    
022    Linking this library statically or dynamically with other modules is
023    making a combined work based on this library.  Thus, the terms and
024    conditions of the GNU General Public License cover the whole
025    combination.
026    
027    As a special exception, the copyright holders of this library give you
028    permission to link this library with independent modules to produce an
029    executable, regardless of the license terms of these independent
030    modules, and to copy and distribute the resulting executable under
031    terms of your choice, provided that you also meet, for each linked
032    independent module, the terms and conditions of the license of that
033    module.  An independent module is a module which is not derived from
034    or based on this library.  If you modify this library, you may extend
035    this exception to your version of the library, but you are not
036    obligated to do so.  If you do not wish to do so, delete this
037    exception statement from your version. */
038    
039    package java.lang;
040    
041    import gnu.java.lang.CPStringBuilder;
042    
043    /**
044     * Instances of class <code>Double</code> represent primitive
045     * <code>double</code> values.
046     *
047     * Additionally, this class provides various helper functions and variables
048     * related to doubles.
049     *
050     * @author Paul Fisher
051     * @author Andrew Haley (aph@cygnus.com)
052     * @author Eric Blake (ebb9@email.byu.edu)
053     * @author Tom Tromey (tromey@redhat.com)
054     * @author Andrew John Hughes (gnu_andrew@member.fsf.org)
055     * @since 1.0
056     * @status partly updated to 1.5
057     */
058    public final class Double extends Number implements Comparable<Double>
059    {
060      /**
061       * Compatible with JDK 1.0+.
062       */
063      private static final long serialVersionUID = -9172774392245257468L;
064    
065      /**
066       * The maximum positive value a <code>double</code> may represent
067       * is 1.7976931348623157e+308.
068       */
069      public static final double MAX_VALUE = 1.7976931348623157e+308;
070    
071      /**
072       * The minimum positive value a <code>double</code> may represent
073       * is 5e-324.
074       */
075      public static final double MIN_VALUE = 5e-324;
076    
077      /**
078       * The value of a double representation -1.0/0.0, negative
079       * infinity.
080       */
081      public static final double NEGATIVE_INFINITY = -1.0 / 0.0;
082    
083      /**
084       * The value of a double representing 1.0/0.0, positive infinity.
085       */
086      public static final double POSITIVE_INFINITY = 1.0 / 0.0;
087    
088      /**
089       * All IEEE 754 values of NaN have the same value in Java.
090       */
091      public static final double NaN = 0.0 / 0.0;
092    
093      /**
094       * The number of bits needed to represent a <code>double</code>.
095       * @since 1.5
096       */
097      public static final int SIZE = 64;
098    
099     /**
100       * The primitive type <code>double</code> is represented by this
101       * <code>Class</code> object.
102       * @since 1.1
103       */
104      public static final Class<Double> TYPE = (Class<Double>) VMClassLoader.getPrimitiveClass('D');
105    
106      /**
107       * Cache representation of 0
108       */
109      private static final Double ZERO = new Double(0.0d);
110    
111      /**
112       * Cache representation of 1
113       */
114      private static final Double ONE = new Double(1.0d);
115    
116      /**
117       * The immutable value of this Double.
118       *
119       * @serial the wrapped double
120       */
121      private final double value;
122    
123      /**
124       * Create a <code>Double</code> from the primitive <code>double</code>
125       * specified.
126       *
127       * @param value the <code>double</code> argument
128       */
129      public Double(double value)
130      {
131        this.value = value;
132      }
133    
134      /**
135       * Create a <code>Double</code> from the specified <code>String</code>.
136       * This method calls <code>Double.parseDouble()</code>.
137       *
138       * @param s the <code>String</code> to convert
139       * @throws NumberFormatException if <code>s</code> cannot be parsed as a
140       *         <code>double</code>
141       * @throws NullPointerException if <code>s</code> is null
142       * @see #parseDouble(String)
143       */
144      public Double(String s)
145      {
146        value = parseDouble(s);
147      }
148    
149      /**
150       * Convert the <code>double</code> to a <code>String</code>.
151       * Floating-point string representation is fairly complex: here is a
152       * rundown of the possible values.  "<code>[-]</code>" indicates that a
153       * negative sign will be printed if the value (or exponent) is negative.
154       * "<code>&lt;number&gt;</code>" means a string of digits ('0' to '9').
155       * "<code>&lt;digit&gt;</code>" means a single digit ('0' to '9').<br>
156       *
157       * <table border=1>
158       * <tr><th>Value of Double</th><th>String Representation</th></tr>
159       * <tr><td>[+-] 0</td> <td><code>[-]0.0</code></td></tr>
160       * <tr><td>Between [+-] 10<sup>-3</sup> and 10<sup>7</sup>, exclusive</td>
161       *     <td><code>[-]number.number</code></td></tr>
162       * <tr><td>Other numeric value</td>
163       *     <td><code>[-]&lt;digit&gt;.&lt;number&gt;
164       *          E[-]&lt;number&gt;</code></td></tr>
165       * <tr><td>[+-] infinity</td> <td><code>[-]Infinity</code></td></tr>
166       * <tr><td>NaN</td> <td><code>NaN</code></td></tr>
167       * </table>
168       *
169       * Yes, negative zero <em>is</em> a possible value.  Note that there is
170       * <em>always</em> a <code>.</code> and at least one digit printed after
171       * it: even if the number is 3, it will be printed as <code>3.0</code>.
172       * After the ".", all digits will be printed except trailing zeros. The
173       * result is rounded to the shortest decimal number which will parse back
174       * to the same double.
175       *
176       * <p>To create other output formats, use {@link java.text.NumberFormat}.
177       *
178       * @XXX specify where we are not in accord with the spec.
179       *
180       * @param d the <code>double</code> to convert
181       * @return the <code>String</code> representing the <code>double</code>
182       */
183      public static String toString(double d)
184      {
185        return VMDouble.toString(d, false);
186      }
187    
188      /**
189       * Convert a double value to a hexadecimal string.  This converts as
190       * follows:
191       * <ul>
192       * <li> A NaN value is converted to the string "NaN".
193       * <li> Positive infinity is converted to the string "Infinity".
194       * <li> Negative infinity is converted to the string "-Infinity".
195       * <li> For all other values, the first character of the result is '-'
196       * if the value is negative.  This is followed by '0x1.' if the
197       * value is normal, and '0x0.' if the value is denormal.  This is
198       * then followed by a (lower-case) hexadecimal representation of the
199       * mantissa, with leading zeros as required for denormal values.
200       * The next character is a 'p', and this is followed by a decimal
201       * representation of the unbiased exponent.
202       * </ul>
203       * @param d the double value
204       * @return the hexadecimal string representation
205       * @since 1.5
206       */
207      public static String toHexString(double d)
208      {
209        if (isNaN(d))
210          return "NaN";
211        if (isInfinite(d))
212          return d < 0 ? "-Infinity" : "Infinity";
213    
214        long bits = doubleToLongBits(d);
215        CPStringBuilder result = new CPStringBuilder();
216        
217        if (bits < 0)
218          result.append('-');
219        result.append("0x");
220    
221        final int mantissaBits = 52;
222        final int exponentBits = 11;
223        long mantMask = (1L << mantissaBits) - 1;
224        long mantissa = bits & mantMask;
225        long expMask = (1L << exponentBits) - 1;
226        long exponent = (bits >>> mantissaBits) & expMask;
227    
228        result.append(exponent == 0 ? '0' : '1');
229        result.append('.');
230        result.append(Long.toHexString(mantissa));
231        if (exponent == 0 && mantissa != 0)
232          {
233            // Treat denormal specially by inserting '0's to make
234            // the length come out right.  The constants here are
235            // to account for things like the '0x'.
236            int offset = 4 + ((bits < 0) ? 1 : 0);
237            // The silly +3 is here to keep the code the same between
238            // the Float and Double cases.  In Float the value is
239            // not a multiple of 4.
240            int desiredLength = offset + (mantissaBits + 3) / 4;
241            while (result.length() < desiredLength)
242              result.insert(offset, '0');
243          }
244        result.append('p');
245        if (exponent == 0 && mantissa == 0)
246          {
247            // Zero, so do nothing special.
248          }
249        else
250          {
251            // Apply bias.
252            boolean denormal = exponent == 0;
253            exponent -= (1 << (exponentBits - 1)) - 1;
254            // Handle denormal.
255            if (denormal)
256              ++exponent;
257          }
258    
259        result.append(Long.toString(exponent));
260        return result.toString();
261      }
262    
263      /**
264       * Returns a <code>Double</code> object wrapping the value.
265       * In contrast to the <code>Double</code> constructor, this method
266       * may cache some values.  It is used by boxing conversion.
267       *
268       * @param val the value to wrap
269       * @return the <code>Double</code>
270       * @since 1.5
271       */
272      public static Double valueOf(double val)
273      {
274        if ((val == 0.0) && (doubleToRawLongBits(val) == 0L))
275          return ZERO;
276        else if (val == 1.0)
277          return ONE;
278        else
279          return new Double(val);
280      }
281    
282     /**
283       * Create a new <code>Double</code> object using the <code>String</code>.
284       *
285       * @param s the <code>String</code> to convert
286       * @return the new <code>Double</code>
287       * @throws NumberFormatException if <code>s</code> cannot be parsed as a
288       *         <code>double</code>
289       * @throws NullPointerException if <code>s</code> is null.
290       * @see #parseDouble(String)
291       */
292      public static Double valueOf(String s)
293      {
294        return valueOf(parseDouble(s));
295      }
296    
297      /**
298       * Parse the specified <code>String</code> as a <code>double</code>. The
299       * extended BNF grammar is as follows:<br>
300       * <pre>
301       * <em>DecodableString</em>:
302       *      ( [ <code>-</code> | <code>+</code> ] <code>NaN</code> )
303       *    | ( [ <code>-</code> | <code>+</code> ] <code>Infinity</code> )
304       *    | ( [ <code>-</code> | <code>+</code> ] <em>FloatingPoint</em>
305       *              [ <code>f</code> | <code>F</code> | <code>d</code>
306       *                | <code>D</code>] )
307       * <em>FloatingPoint</em>:
308       *      ( { <em>Digit</em> }+ [ <code>.</code> { <em>Digit</em> } ]
309       *              [ <em>Exponent</em> ] )
310       *    | ( <code>.</code> { <em>Digit</em> }+ [ <em>Exponent</em> ] )
311       * <em>Exponent</em>:
312       *      ( ( <code>e</code> | <code>E</code> )
313       *              [ <code>-</code> | <code>+</code> ] { <em>Digit</em> }+ )
314       * <em>Digit</em>: <em><code>'0'</code> through <code>'9'</code></em>
315       * </pre>
316       *
317       * <p>NaN and infinity are special cases, to allow parsing of the output
318       * of toString.  Otherwise, the result is determined by calculating
319       * <em>n * 10<sup>exponent</sup></em> to infinite precision, then rounding
320       * to the nearest double. Remember that many numbers cannot be precisely
321       * represented in floating point. In case of overflow, infinity is used,
322       * and in case of underflow, signed zero is used. Unlike Integer.parseInt,
323       * this does not accept Unicode digits outside the ASCII range.
324       *
325       * <p>If an unexpected character is found in the <code>String</code>, a
326       * <code>NumberFormatException</code> will be thrown.  Leading and trailing
327       * 'whitespace' is ignored via <code>String.trim()</code>, but spaces
328       * internal to the actual number are not allowed.
329       *
330       * <p>To parse numbers according to another format, consider using
331       * {@link java.text.NumberFormat}.
332       *
333       * @XXX specify where/how we are not in accord with the spec.
334       *
335       * @param str the <code>String</code> to convert
336       * @return the <code>double</code> value of <code>s</code>
337       * @throws NumberFormatException if <code>s</code> cannot be parsed as a
338       *         <code>double</code>
339       * @throws NullPointerException if <code>s</code> is null
340       * @see #MIN_VALUE
341       * @see #MAX_VALUE
342       * @see #POSITIVE_INFINITY
343       * @see #NEGATIVE_INFINITY
344       * @since 1.2
345       */
346      public static double parseDouble(String str)
347      {
348        return VMDouble.parseDouble(str);
349      }
350    
351      /**
352       * Return <code>true</code> if the <code>double</code> has the same
353       * value as <code>NaN</code>, otherwise return <code>false</code>.
354       *
355       * @param v the <code>double</code> to compare
356       * @return whether the argument is <code>NaN</code>.
357       */
358      public static boolean isNaN(double v)
359      {
360        // This works since NaN != NaN is the only reflexive inequality
361        // comparison which returns true.
362        return v != v;
363      }
364    
365      /**
366       * Return <code>true</code> if the <code>double</code> has a value
367       * equal to either <code>NEGATIVE_INFINITY</code> or
368       * <code>POSITIVE_INFINITY</code>, otherwise return <code>false</code>.
369       *
370       * @param v the <code>double</code> to compare
371       * @return whether the argument is (-/+) infinity.
372       */
373      public static boolean isInfinite(double v)
374      {
375        return v == POSITIVE_INFINITY || v == NEGATIVE_INFINITY;
376      }
377    
378      /**
379       * Return <code>true</code> if the value of this <code>Double</code>
380       * is the same as <code>NaN</code>, otherwise return <code>false</code>.
381       *
382       * @return whether this <code>Double</code> is <code>NaN</code>
383       */
384      public boolean isNaN()
385      {
386        return isNaN(value);
387      }
388    
389      /**
390       * Return <code>true</code> if the value of this <code>Double</code>
391       * is the same as <code>NEGATIVE_INFINITY</code> or
392       * <code>POSITIVE_INFINITY</code>, otherwise return <code>false</code>.
393       *
394       * @return whether this <code>Double</code> is (-/+) infinity
395       */
396      public boolean isInfinite()
397      {
398        return isInfinite(value);
399      }
400    
401      /**
402       * Convert the <code>double</code> value of this <code>Double</code>
403       * to a <code>String</code>.  This method calls
404       * <code>Double.toString(double)</code> to do its dirty work.
405       *
406       * @return the <code>String</code> representation
407       * @see #toString(double)
408       */
409      public String toString()
410      {
411        return toString(value);
412      }
413    
414      /**
415       * Return the value of this <code>Double</code> as a <code>byte</code>.
416       *
417       * @return the byte value
418       * @since 1.1
419       */
420      public byte byteValue()
421      {
422        return (byte) value;
423      }
424    
425      /**
426       * Return the value of this <code>Double</code> as a <code>short</code>.
427       *
428       * @return the short value
429       * @since 1.1
430       */
431      public short shortValue()
432      {
433        return (short) value;
434      }
435    
436      /**
437       * Return the value of this <code>Double</code> as an <code>int</code>.
438       *
439       * @return the int value
440       */
441      public int intValue()
442      {
443        return (int) value;
444      }
445    
446      /**
447       * Return the value of this <code>Double</code> as a <code>long</code>.
448       *
449       * @return the long value
450       */
451      public long longValue()
452      {
453        return (long) value;
454      }
455    
456      /**
457       * Return the value of this <code>Double</code> as a <code>float</code>.
458       *
459       * @return the float value
460       */
461      public float floatValue()
462      {
463        return (float) value;
464      }
465    
466      /**
467       * Return the value of this <code>Double</code>.
468       *
469       * @return the double value
470       */
471      public double doubleValue()
472      {
473        return value;
474      }
475    
476      /**
477       * Return a hashcode representing this Object. <code>Double</code>'s hash
478       * code is calculated by:<br>
479       * <code>long v = Double.doubleToLongBits(doubleValue());<br>
480       *    int hash = (int)(v^(v&gt;&gt;32))</code>.
481       *
482       * @return this Object's hash code
483       * @see #doubleToLongBits(double)
484       */
485      public int hashCode()
486      {
487        long v = doubleToLongBits(value);
488        return (int) (v ^ (v >>> 32));
489      }
490    
491      /**
492       * Returns <code>true</code> if <code>obj</code> is an instance of
493       * <code>Double</code> and represents the same double value. Unlike comparing
494       * two doubles with <code>==</code>, this treats two instances of
495       * <code>Double.NaN</code> as equal, but treats <code>0.0</code> and
496       * <code>-0.0</code> as unequal.
497       *
498       * <p>Note that <code>d1.equals(d2)</code> is identical to
499       * <code>doubleToLongBits(d1.doubleValue()) ==
500       *    doubleToLongBits(d2.doubleValue())</code>.
501       *
502       * @param obj the object to compare
503       * @return whether the objects are semantically equal
504       */
505      public boolean equals(Object obj)
506      {
507        if (obj instanceof Double)
508          {
509            double d = ((Double) obj).value;
510            return (doubleToRawLongBits(value) == doubleToRawLongBits(d)) ||
511              (isNaN(value) && isNaN(d));
512          }
513        return false;
514      }
515    
516      /**
517       * Convert the double to the IEEE 754 floating-point "double format" bit
518       * layout. Bit 63 (the most significant) is the sign bit, bits 62-52
519       * (masked by 0x7ff0000000000000L) represent the exponent, and bits 51-0
520       * (masked by 0x000fffffffffffffL) are the mantissa. This function
521       * collapses all versions of NaN to 0x7ff8000000000000L. The result of this
522       * function can be used as the argument to
523       * <code>Double.longBitsToDouble(long)</code> to obtain the original
524       * <code>double</code> value.
525       *
526       * @param value the <code>double</code> to convert
527       * @return the bits of the <code>double</code>
528       * @see #longBitsToDouble(long)
529       */
530      public static long doubleToLongBits(double value)
531      {
532        if (isNaN(value))
533          return 0x7ff8000000000000L;
534        else
535          return VMDouble.doubleToRawLongBits(value);
536      }
537    
538      /**
539       * Convert the double to the IEEE 754 floating-point "double format" bit
540       * layout. Bit 63 (the most significant) is the sign bit, bits 62-52
541       * (masked by 0x7ff0000000000000L) represent the exponent, and bits 51-0
542       * (masked by 0x000fffffffffffffL) are the mantissa. This function
543       * leaves NaN alone, rather than collapsing to a canonical value. The
544       * result of this function can be used as the argument to
545       * <code>Double.longBitsToDouble(long)</code> to obtain the original
546       * <code>double</code> value.
547       *
548       * @param value the <code>double</code> to convert
549       * @return the bits of the <code>double</code>
550       * @see #longBitsToDouble(long)
551       */
552      public static long doubleToRawLongBits(double value)
553      {
554        return VMDouble.doubleToRawLongBits(value);
555      }
556    
557      /**
558       * Convert the argument in IEEE 754 floating-point "double format" bit
559       * layout to the corresponding float. Bit 63 (the most significant) is the
560       * sign bit, bits 62-52 (masked by 0x7ff0000000000000L) represent the
561       * exponent, and bits 51-0 (masked by 0x000fffffffffffffL) are the mantissa.
562       * This function leaves NaN alone, so that you can recover the bit pattern
563       * with <code>Double.doubleToRawLongBits(double)</code>.
564       *
565       * @param bits the bits to convert
566       * @return the <code>double</code> represented by the bits
567       * @see #doubleToLongBits(double)
568       * @see #doubleToRawLongBits(double)
569       */
570      public static double longBitsToDouble(long bits)
571      {
572        return VMDouble.longBitsToDouble(bits);
573      }
574    
575      /**
576       * Compare two Doubles numerically by comparing their <code>double</code>
577       * values. The result is positive if the first is greater, negative if the
578       * second is greater, and 0 if the two are equal. However, this special
579       * cases NaN and signed zero as follows: NaN is considered greater than
580       * all other doubles, including <code>POSITIVE_INFINITY</code>, and positive
581       * zero is considered greater than negative zero.
582       *
583       * @param d the Double to compare
584       * @return the comparison
585       * @since 1.2
586       */
587      public int compareTo(Double d)
588      {
589        return compare(value, d.value);
590      }
591    
592      /**
593       * Behaves like <code>new Double(x).compareTo(new Double(y))</code>; in
594       * other words this compares two doubles, special casing NaN and zero,
595       * without the overhead of objects.
596       *
597       * @param x the first double to compare
598       * @param y the second double to compare
599       * @return the comparison
600       * @since 1.4
601       */
602      public static int compare(double x, double y)
603      {
604          // handle the easy cases:
605          if (x < y)
606              return -1;
607          if (x > y)
608              return 1;
609    
610          // handle equality respecting that 0.0 != -0.0 (hence not using x == y):
611          long lx = doubleToRawLongBits(x);
612          long ly = doubleToRawLongBits(y);
613          if (lx == ly)
614              return 0;
615    
616          // handle NaNs:
617          if (x != x)
618              return (y != y) ? 0 : 1;
619          else if (y != y)
620              return -1;
621    
622          // handle +/- 0.0
623          return (lx < ly) ? -1 : 1;
624      }
625    }