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><number></code>" means a string of digits ('0' to '9').
144 * "<code><digit></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>[-]<digit>.<number>
153 * E[-]<number></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>>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 }