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