001 /*
002 * Copyright 1994-2006 Sun Microsystems, Inc. All Rights Reserved.
003 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
004 *
005 * This code is free software; you can redistribute it and/or modify it
006 * under the terms of the GNU General Public License version 2 only, as
007 * published by the Free Software Foundation. Sun designates this
008 * particular file as subject to the "Classpath" exception as provided
009 * by Sun in the LICENSE file that accompanied this code.
010 *
011 * This code is distributed in the hope that it will be useful, but WITHOUT
012 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
013 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
014 * version 2 for more details (a copy is included in the LICENSE file that
015 * accompanied this code).
016 *
017 * You should have received a copy of the GNU General Public License version
018 * 2 along with this work; if not, write to the Free Software Foundation,
019 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
020 *
021 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
022 * CA 95054 USA or visit www.sun.com if you need additional information or
023 * have any questions.
024 */
025
026 package java.lang;
027
028 import sun.misc.FloatingDecimal;
029 import sun.misc.FpUtils;
030 import sun.misc.DoubleConsts;
031
032 /**
033 * The {@code Double} class wraps a value of the primitive type
034 * {@code double} in an object. An object of type
035 * {@code Double} contains a single field whose type is
036 * {@code double}.
037 *
038 * <p>In addition, this class provides several methods for converting a
039 * {@code double} to a {@code String} and a
040 * {@code String} to a {@code double}, as well as other
041 * constants and methods useful when dealing with a
042 * {@code double}.
043 *
044 * @author Lee Boynton
045 * @author Arthur van Hoff
046 * @author Joseph D. Darcy
047 * @version 1.108, 06/12/07
048 * @since JDK1.0
049 */
050 public final class Double extends Number implements Comparable<Double> {
051 /**
052 * A constant holding the positive infinity of type
053 * {@code double}. It is equal to the value returned by
054 * {@code Double.longBitsToDouble(0x7ff0000000000000L)}.
055 */
056 public static final double POSITIVE_INFINITY = 1.0 / 0.0;
057
058 /**
059 * A constant holding the negative infinity of type
060 * {@code double}. It is equal to the value returned by
061 * {@code Double.longBitsToDouble(0xfff0000000000000L)}.
062 */
063 public static final double NEGATIVE_INFINITY = -1.0 / 0.0;
064
065 /**
066 * A constant holding a Not-a-Number (NaN) value of type
067 * {@code double}. It is equivalent to the value returned by
068 * {@code Double.longBitsToDouble(0x7ff8000000000000L)}.
069 */
070 public static final double NaN = 0.0d / 0.0;
071
072 /**
073 * A constant holding the largest positive finite value of type
074 * {@code double},
075 * (2-2<sup>-52</sup>)·2<sup>1023</sup>. It is equal to
076 * the hexadecimal floating-point literal
077 * {@code 0x1.fffffffffffffP+1023} and also equal to
078 * {@code Double.longBitsToDouble(0x7fefffffffffffffL)}.
079 */
080 public static final double MAX_VALUE = 0x1.fffffffffffffP+1023; // 1.7976931348623157e+308
081
082 /**
083 * A constant holding the smallest positive normal value of type
084 * {@code double}, 2<sup>-1022</sup>. It is equal to the
085 * hexadecimal floating-point literal {@code 0x1.0p-1022} and also
086 * equal to {@code Double.longBitsToDouble(0x0010000000000000L)}.
087 *
088 * @since 1.6
089 */
090 public static final double MIN_NORMAL = 0x1.0p-1022; // 2.2250738585072014E-308
091
092 /**
093 * A constant holding the smallest positive nonzero value of type
094 * {@code double}, 2<sup>-1074</sup>. It is equal to the
095 * hexadecimal floating-point literal
096 * {@code 0x0.0000000000001P-1022} and also equal to
097 * {@code Double.longBitsToDouble(0x1L)}.
098 */
099 public static final double MIN_VALUE = 0x0.0000000000001P-1022; // 4.9e-324
100
101 /**
102 * Maximum exponent a finite {@code double} variable may have.
103 * It is equal to the value returned by
104 * {@code Math.getExponent(Double.MAX_VALUE)}.
105 *
106 * @since 1.6
107 */
108 public static final int MAX_EXPONENT = 1023;
109
110 /**
111 * Minimum exponent a normalized {@code double} variable may
112 * have. It is equal to the value returned by
113 * {@code Math.getExponent(Double.MIN_NORMAL)}.
114 *
115 * @since 1.6
116 */
117 public static final int MIN_EXPONENT = -1022;
118
119 /**
120 * The number of bits used to represent a {@code double} value.
121 *
122 * @since 1.5
123 */
124 public static final int SIZE = 64;
125
126 /**
127 * The {@code Class} instance representing the primitive type
128 * {@code double}.
129 *
130 * @since JDK1.1
131 */
132 public static final Class<Double> TYPE = (Class<Double>) Class
133 .getPrimitiveClass("double");
134
135 /**
136 * Returns a string representation of the {@code double}
137 * argument. All characters mentioned below are ASCII characters.
138 * <ul>
139 * <li>If the argument is NaN, the result is the string
140 * "{@code NaN}".
141 * <li>Otherwise, the result is a string that represents the sign and
142 * magnitude (absolute value) of the argument. If the sign is negative,
143 * the first character of the result is '{@code -}'
144 * (<code>'\u002D'</code>); if the sign is positive, no sign character
145 * appears in the result. As for the magnitude <i>m</i>:
146 * <ul>
147 * <li>If <i>m</i> is infinity, it is represented by the characters
148 * {@code "Infinity"}; thus, positive infinity produces the result
149 * {@code "Infinity"} and negative infinity produces the result
150 * {@code "-Infinity"}.
151 *
152 * <li>If <i>m</i> is zero, it is represented by the characters
153 * {@code "0.0"}; thus, negative zero produces the result
154 * {@code "-0.0"} and positive zero produces the result
155 * {@code "0.0"}.
156 *
157 * <li>If <i>m</i> is greater than or equal to 10<sup>-3</sup> but less
158 * than 10<sup>7</sup>, then it is represented as the integer part of
159 * <i>m</i>, in decimal form with no leading zeroes, followed by
160 * '{@code .}' (<code>'\u002E'</code>), followed by one or
161 * more decimal digits representing the fractional part of <i>m</i>.
162 *
163 * <li>If <i>m</i> is less than 10<sup>-3</sup> or greater than or
164 * equal to 10<sup>7</sup>, then it is represented in so-called
165 * "computerized scientific notation." Let <i>n</i> be the unique
166 * integer such that 10<sup><i>n</i></sup> ≤ <i>m</i> {@literal <}
167 * 10<sup><i>n</i>+1</sup>; then let <i>a</i> be the
168 * mathematically exact quotient of <i>m</i> and
169 * 10<sup><i>n</i></sup> so that 1 ≤ <i>a</i> {@literal <} 10. The
170 * magnitude is then represented as the integer part of <i>a</i>,
171 * as a single decimal digit, followed by '{@code .}'
172 * (<code>'\u002E'</code>), followed by decimal digits
173 * representing the fractional part of <i>a</i>, followed by the
174 * letter '{@code E}' (<code>'\u0045'</code>), followed
175 * by a representation of <i>n</i> as a decimal integer, as
176 * produced by the method {@link Integer#toString(int)}.
177 * </ul>
178 * </ul>
179 * How many digits must be printed for the fractional part of
180 * <i>m</i> or <i>a</i>? There must be at least one digit to represent
181 * the fractional part, and beyond that as many, but only as many, more
182 * digits as are needed to uniquely distinguish the argument value from
183 * adjacent values of type {@code double}. That is, suppose that
184 * <i>x</i> is the exact mathematical value represented by the decimal
185 * representation produced by this method for a finite nonzero argument
186 * <i>d</i>. Then <i>d</i> must be the {@code double} value nearest
187 * to <i>x</i>; or if two {@code double} values are equally close
188 * to <i>x</i>, then <i>d</i> must be one of them and the least
189 * significant bit of the significand of <i>d</i> must be {@code 0}.
190 *
191 * <p>To create localized string representations of a floating-point
192 * value, use subclasses of {@link java.text.NumberFormat}.
193 *
194 * @param d the {@code double} to be converted.
195 * @return a string representation of the argument.
196 */
197 public static String toString(double d) {
198 return new FloatingDecimal(d).toJavaFormatString();
199 }
200
201 /**
202 * Returns a hexadecimal string representation of the
203 * {@code double} argument. All characters mentioned below
204 * are ASCII characters.
205 *
206 * <ul>
207 * <li>If the argument is NaN, the result is the string
208 * "{@code NaN}".
209 * <li>Otherwise, the result is a string that represents the sign
210 * and magnitude of the argument. If the sign is negative, the
211 * first character of the result is '{@code -}'
212 * (<code>'\u002D'</code>); if the sign is positive, no sign
213 * character appears in the result. As for the magnitude <i>m</i>:
214 *
215 * <ul>
216 * <li>If <i>m</i> is infinity, it is represented by the string
217 * {@code "Infinity"}; thus, positive infinity produces the
218 * result {@code "Infinity"} and negative infinity produces
219 * the result {@code "-Infinity"}.
220 *
221 * <li>If <i>m</i> is zero, it is represented by the string
222 * {@code "0x0.0p0"}; thus, negative zero produces the result
223 * {@code "-0x0.0p0"} and positive zero produces the result
224 * {@code "0x0.0p0"}.
225 *
226 * <li>If <i>m</i> is a {@code double} value with a
227 * normalized representation, substrings are used to represent the
228 * significand and exponent fields. The significand is
229 * represented by the characters {@code "0x1."}
230 * followed by a lowercase hexadecimal representation of the rest
231 * of the significand as a fraction. Trailing zeros in the
232 * hexadecimal representation are removed unless all the digits
233 * are zero, in which case a single zero is used. Next, the
234 * exponent is represented by {@code "p"} followed
235 * by a decimal string of the unbiased exponent as if produced by
236 * a call to {@link Integer#toString(int) Integer.toString} on the
237 * exponent value.
238 *
239 * <li>If <i>m</i> is a {@code double} value with a subnormal
240 * representation, the significand is represented by the
241 * characters {@code "0x0."} followed by a
242 * hexadecimal representation of the rest of the significand as a
243 * fraction. Trailing zeros in the hexadecimal representation are
244 * removed. Next, the exponent is represented by
245 * {@code "p-1022"}. Note that there must be at
246 * least one nonzero digit in a subnormal significand.
247 *
248 * </ul>
249 *
250 * </ul>
251 *
252 * <table border>
253 * <caption><h3>Examples</h3></caption>
254 * <tr><th>Floating-point Value</th><th>Hexadecimal String</th>
255 * <tr><td>{@code 1.0}</td> <td>{@code 0x1.0p0}</td>
256 * <tr><td>{@code -1.0}</td> <td>{@code -0x1.0p0}</td>
257 * <tr><td>{@code 2.0}</td> <td>{@code 0x1.0p1}</td>
258 * <tr><td>{@code 3.0}</td> <td>{@code 0x1.8p1}</td>
259 * <tr><td>{@code 0.5}</td> <td>{@code 0x1.0p-1}</td>
260 * <tr><td>{@code 0.25}</td> <td>{@code 0x1.0p-2}</td>
261 * <tr><td>{@code Double.MAX_VALUE}</td>
262 * <td>{@code 0x1.fffffffffffffp1023}</td>
263 * <tr><td>{@code Minimum Normal Value}</td>
264 * <td>{@code 0x1.0p-1022}</td>
265 * <tr><td>{@code Maximum Subnormal Value}</td>
266 * <td>{@code 0x0.fffffffffffffp-1022}</td>
267 * <tr><td>{@code Double.MIN_VALUE}</td>
268 * <td>{@code 0x0.0000000000001p-1022}</td>
269 * </table>
270 * @param d the {@code double} to be converted.
271 * @return a hex string representation of the argument.
272 * @since 1.5
273 * @author Joseph D. Darcy
274 */
275 public static String toHexString(double d) {
276 /*
277 * Modeled after the "a" conversion specifier in C99, section
278 * 7.19.6.1; however, the output of this method is more
279 * tightly specified.
280 */
281 if (!FpUtils.isFinite(d))
282 // For infinity and NaN, use the decimal output.
283 return Double.toString(d);
284 else {
285 // Initialized to maximum size of output.
286 StringBuffer answer = new StringBuffer(24);
287
288 if (FpUtils.rawCopySign(1.0, d) == -1.0) // value is negative,
289 answer.append("-"); // so append sign info
290
291 answer.append("0x");
292
293 d = Math.abs(d);
294
295 if (d == 0.0) {
296 answer.append("0.0p0");
297 } else {
298 boolean subnormal = (d < DoubleConsts.MIN_NORMAL);
299
300 // Isolate significand bits and OR in a high-order bit
301 // so that the string representation has a known
302 // length.
303 long signifBits = (Double.doubleToLongBits(d) & DoubleConsts.SIGNIF_BIT_MASK) | 0x1000000000000000L;
304
305 // Subnormal values have a 0 implicit bit; normal
306 // values have a 1 implicit bit.
307 answer.append(subnormal ? "0." : "1.");
308
309 // Isolate the low-order 13 digits of the hex
310 // representation. If all the digits are zero,
311 // replace with a single 0; otherwise, remove all
312 // trailing zeros.
313 String signif = Long.toHexString(signifBits).substring(
314 3, 16);
315 answer.append(signif.equals("0000000000000") ? // 13 zeros
316 "0"
317 : signif.replaceFirst("0{1,12}$", ""));
318
319 // If the value is subnormal, use the E_min exponent
320 // value for double; otherwise, extract and report d's
321 // exponent (the representation of a subnormal uses
322 // E_min -1).
323 answer.append("p"
324 + (subnormal ? DoubleConsts.MIN_EXPONENT
325 : FpUtils.getExponent(d)));
326 }
327 return answer.toString();
328 }
329 }
330
331 /**
332 * Returns a {@code Double} object holding the
333 * {@code double} value represented by the argument string
334 * {@code s}.
335 *
336 * <p>If {@code s} is {@code null}, then a
337 * {@code NullPointerException} is thrown.
338 *
339 * <p>Leading and trailing whitespace characters in {@code s}
340 * are ignored. Whitespace is removed as if by the {@link
341 * String#trim} method; that is, both ASCII space and control
342 * characters are removed. The rest of {@code s} should
343 * constitute a <i>FloatValue</i> as described by the lexical
344 * syntax rules:
345 *
346 * <blockquote>
347 * <dl>
348 * <dt><i>FloatValue:</i>
349 * <dd><i>Sign<sub>opt</sub></i> {@code NaN}
350 * <dd><i>Sign<sub>opt</sub></i> {@code Infinity}
351 * <dd><i>Sign<sub>opt</sub> FloatingPointLiteral</i>
352 * <dd><i>Sign<sub>opt</sub> HexFloatingPointLiteral</i>
353 * <dd><i>SignedInteger</i>
354 * </dl>
355 *
356 * <p>
357 *
358 * <dl>
359 * <dt><i>HexFloatingPointLiteral</i>:
360 * <dd> <i>HexSignificand BinaryExponent FloatTypeSuffix<sub>opt</sub></i>
361 * </dl>
362 *
363 * <p>
364 *
365 * <dl>
366 * <dt><i>HexSignificand:</i>
367 * <dd><i>HexNumeral</i>
368 * <dd><i>HexNumeral</i> {@code .}
369 * <dd>{@code 0x} <i>HexDigits<sub>opt</sub>
370 * </i>{@code .}<i> HexDigits</i>
371 * <dd>{@code 0X}<i> HexDigits<sub>opt</sub>
372 * </i>{@code .} <i>HexDigits</i>
373 * </dl>
374 *
375 * <p>
376 *
377 * <dl>
378 * <dt><i>BinaryExponent:</i>
379 * <dd><i>BinaryExponentIndicator SignedInteger</i>
380 * </dl>
381 *
382 * <p>
383 *
384 * <dl>
385 * <dt><i>BinaryExponentIndicator:</i>
386 * <dd>{@code p}
387 * <dd>{@code P}
388 * </dl>
389 *
390 * </blockquote>
391 *
392 * where <i>Sign</i>, <i>FloatingPointLiteral</i>,
393 * <i>HexNumeral</i>, <i>HexDigits</i>, <i>SignedInteger</i> and
394 * <i>FloatTypeSuffix</i> are as defined in the lexical structure
395 * sections of the <a
396 * href="http://java.sun.com/docs/books/jls/html/">Java Language
397 * Specification</a>. If {@code s} does not have the form of
398 * a <i>FloatValue</i>, then a {@code NumberFormatException}
399 * is thrown. Otherwise, {@code s} is regarded as
400 * representing an exact decimal value in the usual
401 * "computerized scientific notation" or as an exact
402 * hexadecimal value; this exact numerical value is then
403 * conceptually converted to an "infinitely precise"
404 * binary value that is then rounded to type {@code double}
405 * by the usual round-to-nearest rule of IEEE 754 floating-point
406 * arithmetic, which includes preserving the sign of a zero
407 * value. Finally, a {@code Double} object representing this
408 * {@code double} value is returned.
409 *
410 * <p> To interpret localized string representations of a
411 * floating-point value, use subclasses of {@link
412 * java.text.NumberFormat}.
413 *
414 * <p>Note that trailing format specifiers, specifiers that
415 * determine the type of a floating-point literal
416 * ({@code 1.0f} is a {@code float} value;
417 * {@code 1.0d} is a {@code double} value), do
418 * <em>not</em> influence the results of this method. In other
419 * words, the numerical value of the input string is converted
420 * directly to the target floating-point type. The two-step
421 * sequence of conversions, string to {@code float} followed
422 * by {@code float} to {@code double}, is <em>not</em>
423 * equivalent to converting a string directly to
424 * {@code double}. For example, the {@code float}
425 * literal {@code 0.1f} is equal to the {@code double}
426 * value {@code 0.10000000149011612}; the {@code float}
427 * literal {@code 0.1f} represents a different numerical
428 * value than the {@code double} literal
429 * {@code 0.1}. (The numerical value 0.1 cannot be exactly
430 * represented in a binary floating-point number.)
431 *
432 * <p>To avoid calling this method on an invalid string and having
433 * a {@code NumberFormatException} be thrown, the regular
434 * expression below can be used to screen the input string:
435 *
436 * <code>
437 * <pre>
438 * final String Digits = "(\\p{Digit}+)";
439 * final String HexDigits = "(\\p{XDigit}+)";
440 * // an exponent is 'e' or 'E' followed by an optionally
441 * // signed decimal integer.
442 * final String Exp = "[eE][+-]?"+Digits;
443 * final String fpRegex =
444 * ("[\\x00-\\x20]*"+ // Optional leading "whitespace"
445 * "[+-]?(" + // Optional sign character
446 * "NaN|" + // "NaN" string
447 * "Infinity|" + // "Infinity" string
448 *
449 * // A decimal floating-point string representing a finite positive
450 * // number without a leading sign has at most five basic pieces:
451 * // Digits . Digits ExponentPart FloatTypeSuffix
452 * //
453 * // Since this method allows integer-only strings as input
454 * // in addition to strings of floating-point literals, the
455 * // two sub-patterns below are simplifications of the grammar
456 * // productions from the Java Language Specification, 2nd
457 * // edition, section 3.10.2.
458 *
459 * // Digits ._opt Digits_opt ExponentPart_opt FloatTypeSuffix_opt
460 * "((("+Digits+"(\\.)?("+Digits+"?)("+Exp+")?)|"+
461 *
462 * // . Digits ExponentPart_opt FloatTypeSuffix_opt
463 * "(\\.("+Digits+")("+Exp+")?)|"+
464 *
465 * // Hexadecimal strings
466 * "((" +
467 * // 0[xX] HexDigits ._opt BinaryExponent FloatTypeSuffix_opt
468 * "(0[xX]" + HexDigits + "(\\.)?)|" +
469 *
470 * // 0[xX] HexDigits_opt . HexDigits BinaryExponent FloatTypeSuffix_opt
471 * "(0[xX]" + HexDigits + "?(\\.)" + HexDigits + ")" +
472 *
473 * ")[pP][+-]?" + Digits + "))" +
474 * "[fFdD]?))" +
475 * "[\\x00-\\x20]*");// Optional trailing "whitespace"
476 *
477 * if (Pattern.matches(fpRegex, myString))
478 * Double.valueOf(myString); // Will not throw NumberFormatException
479 * else {
480 * // Perform suitable alternative action
481 * }
482 * </pre>
483 * </code>
484 *
485 * @param s the string to be parsed.
486 * @return a {@code Double} object holding the value
487 * represented by the {@code String} argument.
488 * @throws NumberFormatException if the string does not contain a
489 * parsable number.
490 */
491 public static Double valueOf(String s) throws NumberFormatException {
492 return new Double(FloatingDecimal.readJavaFormatString(s)
493 .doubleValue());
494 }
495
496 /**
497 * Returns a {@code Double} instance representing the specified
498 * {@code double} value.
499 * If a new {@code Double} instance is not required, this method
500 * should generally be used in preference to the constructor
501 * {@link #Double(double)}, as this method is likely to yield
502 * significantly better space and time performance by caching
503 * frequently requested values.
504 *
505 * @param d a double value.
506 * @return a {@code Double} instance representing {@code d}.
507 * @since 1.5
508 */
509 public static Double valueOf(double d) {
510 return new Double(d);
511 }
512
513 /**
514 * Returns a new {@code double} initialized to the value
515 * represented by the specified {@code String}, as performed
516 * by the {@code valueOf} method of class
517 * {@code Double}.
518 *
519 * @param s the string to be parsed.
520 * @return the {@code double} value represented by the string
521 * argument.
522 * @throws NumberFormatException if the string does not contain
523 * a parsable {@code double}.
524 * @see java.lang.Double#valueOf(String)
525 * @since 1.2
526 */
527 public static double parseDouble(String s)
528 throws NumberFormatException {
529 return FloatingDecimal.readJavaFormatString(s).doubleValue();
530 }
531
532 /**
533 * Returns {@code true} if the specified number is a
534 * Not-a-Number (NaN) value, {@code false} otherwise.
535 *
536 * @param v the value to be tested.
537 * @return {@code true} if the value of the argument is NaN;
538 * {@code false} otherwise.
539 */
540 static public boolean isNaN(double v) {
541 return (v != v);
542 }
543
544 /**
545 * Returns {@code true} if the specified number is infinitely
546 * large in magnitude, {@code false} otherwise.
547 *
548 * @param v the value to be tested.
549 * @return {@code true} if the value of the argument is positive
550 * infinity or negative infinity; {@code false} otherwise.
551 */
552 static public boolean isInfinite(double v) {
553 return (v == POSITIVE_INFINITY) || (v == NEGATIVE_INFINITY);
554 }
555
556 /**
557 * The value of the Double.
558 *
559 * @serial
560 */
561 private final double value;
562
563 /**
564 * Constructs a newly allocated {@code Double} object that
565 * represents the primitive {@code double} argument.
566 *
567 * @param value the value to be represented by the {@code Double}.
568 */
569 public Double(double value) {
570 this .value = value;
571 }
572
573 /**
574 * Constructs a newly allocated {@code Double} object that
575 * represents the floating-point value of type {@code double}
576 * represented by the string. The string is converted to a
577 * {@code double} value as if by the {@code valueOf} method.
578 *
579 * @param s a string to be converted to a {@code Double}.
580 * @throws NumberFormatException if the string does not contain a
581 * parsable number.
582 * @see java.lang.Double#valueOf(java.lang.String)
583 */
584 public Double(String s) throws NumberFormatException {
585 // REMIND: this is inefficient
586 this (valueOf(s).doubleValue());
587 }
588
589 /**
590 * Returns {@code true} if this {@code Double} value is
591 * a Not-a-Number (NaN), {@code false} otherwise.
592 *
593 * @return {@code true} if the value represented by this object is
594 * NaN; {@code false} otherwise.
595 */
596 public boolean isNaN() {
597 return isNaN(value);
598 }
599
600 /**
601 * Returns {@code true} if this {@code Double} value is
602 * infinitely large in magnitude, {@code false} otherwise.
603 *
604 * @return {@code true} if the value represented by this object is
605 * positive infinity or negative infinity;
606 * {@code false} otherwise.
607 */
608 public boolean isInfinite() {
609 return isInfinite(value);
610 }
611
612 /**
613 * Returns a string representation of this {@code Double} object.
614 * The primitive {@code double} value represented by this
615 * object is converted to a string exactly as if by the method
616 * {@code toString} of one argument.
617 *
618 * @return a {@code String} representation of this object.
619 * @see java.lang.Double#toString(double)
620 */
621 public String toString() {
622 return String.valueOf(value);
623 }
624
625 /**
626 * Returns the value of this {@code Double} as a {@code byte} (by
627 * casting to a {@code byte}).
628 *
629 * @return the {@code double} value represented by this object
630 * converted to type {@code byte}
631 * @since JDK1.1
632 */
633 public byte byteValue() {
634 return (byte) value;
635 }
636
637 /**
638 * Returns the value of this {@code Double} as a
639 * {@code short} (by casting to a {@code short}).
640 *
641 * @return the {@code double} value represented by this object
642 * converted to type {@code short}
643 * @since JDK1.1
644 */
645 public short shortValue() {
646 return (short) value;
647 }
648
649 /**
650 * Returns the value of this {@code Double} as an
651 * {@code int} (by casting to type {@code int}).
652 *
653 * @return the {@code double} value represented by this object
654 * converted to type {@code int}
655 */
656 public int intValue() {
657 return (int) value;
658 }
659
660 /**
661 * Returns the value of this {@code Double} as a
662 * {@code long} (by casting to type {@code long}).
663 *
664 * @return the {@code double} value represented by this object
665 * converted to type {@code long}
666 */
667 public long longValue() {
668 return (long) value;
669 }
670
671 /**
672 * Returns the {@code float} value of this
673 * {@code Double} object.
674 *
675 * @return the {@code double} value represented by this object
676 * converted to type {@code float}
677 * @since JDK1.0
678 */
679 public float floatValue() {
680 return (float) value;
681 }
682
683 /**
684 * Returns the {@code double} value of this
685 * {@code Double} object.
686 *
687 * @return the {@code double} value represented by this object
688 */
689 public double doubleValue() {
690 return (double) value;
691 }
692
693 /**
694 * Returns a hash code for this {@code Double} object. The
695 * result is the exclusive OR of the two halves of the
696 * {@code long} integer bit representation, exactly as
697 * produced by the method {@link #doubleToLongBits(double)}, of
698 * the primitive {@code double} value represented by this
699 * {@code Double} object. That is, the hash code is the value
700 * of the expression:
701 *
702 * <blockquote>
703 * {@code (int)(v^(v>>>32))}
704 * </blockquote>
705 *
706 * where {@code v} is defined by:
707 *
708 * <blockquote>
709 * {@code long v = Double.doubleToLongBits(this.doubleValue());}
710 * </blockquote>
711 *
712 * @return a {@code hash code} value for this object.
713 */
714 public int hashCode() {
715 long bits = doubleToLongBits(value);
716 return (int) (bits ^ (bits >>> 32));
717 }
718
719 /**
720 * Compares this object against the specified object. The result
721 * is {@code true} if and only if the argument is not
722 * {@code null} and is a {@code Double} object that
723 * represents a {@code double} that has the same value as the
724 * {@code double} represented by this object. For this
725 * purpose, two {@code double} values are considered to be
726 * the same if and only if the method {@link
727 * #doubleToLongBits(double)} returns the identical
728 * {@code long} value when applied to each.
729 *
730 * <p>Note that in most cases, for two instances of class
731 * {@code Double}, {@code d1} and {@code d2}, the
732 * value of {@code d1.equals(d2)} is {@code true} if and
733 * only if
734 *
735 * <blockquote>
736 * {@code d1.doubleValue() == d2.doubleValue()}
737 * </blockquote>
738 *
739 * <p>also has the value {@code true}. However, there are two
740 * exceptions:
741 * <ul>
742 * <li>If {@code d1} and {@code d2} both represent
743 * {@code Double.NaN}, then the {@code equals} method
744 * returns {@code true}, even though
745 * {@code Double.NaN==Double.NaN} has the value
746 * {@code false}.
747 * <li>If {@code d1} represents {@code +0.0} while
748 * {@code d2} represents {@code -0.0}, or vice versa,
749 * the {@code equal} test has the value {@code false},
750 * even though {@code +0.0==-0.0} has the value {@code true}.
751 * </ul>
752 * This definition allows hash tables to operate properly.
753 * @param obj the object to compare with.
754 * @return {@code true} if the objects are the same;
755 * {@code false} otherwise.
756 * @see java.lang.Double#doubleToLongBits(double)
757 */
758 public boolean equals(Object obj) {
759 return (obj instanceof Double)
760 && (doubleToLongBits(((Double) obj).value) == doubleToLongBits(value));
761 }
762
763 /**
764 * Returns a representation of the specified floating-point value
765 * according to the IEEE 754 floating-point "double
766 * format" bit layout.
767 *
768 * <p>Bit 63 (the bit that is selected by the mask
769 * {@code 0x8000000000000000L}) represents the sign of the
770 * floating-point number. Bits
771 * 62-52 (the bits that are selected by the mask
772 * {@code 0x7ff0000000000000L}) represent the exponent. Bits 51-0
773 * (the bits that are selected by the mask
774 * {@code 0x000fffffffffffffL}) represent the significand
775 * (sometimes called the mantissa) of the floating-point number.
776 *
777 * <p>If the argument is positive infinity, the result is
778 * {@code 0x7ff0000000000000L}.
779 *
780 * <p>If the argument is negative infinity, the result is
781 * {@code 0xfff0000000000000L}.
782 *
783 * <p>If the argument is NaN, the result is
784 * {@code 0x7ff8000000000000L}.
785 *
786 * <p>In all cases, the result is a {@code long} integer that, when
787 * given to the {@link #longBitsToDouble(long)} method, will produce a
788 * floating-point value the same as the argument to
789 * {@code doubleToLongBits} (except all NaN values are
790 * collapsed to a single "canonical" NaN value).
791 *
792 * @param value a {@code double} precision floating-point number.
793 * @return the bits that represent the floating-point number.
794 */
795 public static long doubleToLongBits(double value) {
796 long result = doubleToRawLongBits(value);
797 // Check for NaN based on values of bit fields, maximum
798 // exponent and nonzero significand.
799 if (((result & DoubleConsts.EXP_BIT_MASK) == DoubleConsts.EXP_BIT_MASK)
800 && (result & DoubleConsts.SIGNIF_BIT_MASK) != 0L)
801 result = 0x7ff8000000000000L;
802 return result;
803 }
804
805 /**
806 * Returns a representation of the specified floating-point value
807 * according to the IEEE 754 floating-point "double
808 * format" bit layout, preserving Not-a-Number (NaN) values.
809 *
810 * <p>Bit 63 (the bit that is selected by the mask
811 * {@code 0x8000000000000000L}) represents the sign of the
812 * floating-point number. Bits
813 * 62-52 (the bits that are selected by the mask
814 * {@code 0x7ff0000000000000L}) represent the exponent. Bits 51-0
815 * (the bits that are selected by the mask
816 * {@code 0x000fffffffffffffL}) represent the significand
817 * (sometimes called the mantissa) of the floating-point number.
818 *
819 * <p>If the argument is positive infinity, the result is
820 * {@code 0x7ff0000000000000L}.
821 *
822 * <p>If the argument is negative infinity, the result is
823 * {@code 0xfff0000000000000L}.
824 *
825 * <p>If the argument is NaN, the result is the {@code long}
826 * integer representing the actual NaN value. Unlike the
827 * {@code doubleToLongBits} method,
828 * {@code doubleToRawLongBits} does not collapse all the bit
829 * patterns encoding a NaN to a single "canonical" NaN
830 * value.
831 *
832 * <p>In all cases, the result is a {@code long} integer that,
833 * when given to the {@link #longBitsToDouble(long)} method, will
834 * produce a floating-point value the same as the argument to
835 * {@code doubleToRawLongBits}.
836 *
837 * @param value a {@code double} precision floating-point number.
838 * @return the bits that represent the floating-point number.
839 * @since 1.3
840 */
841 public static native long doubleToRawLongBits(double value);
842
843 /**
844 * Returns the {@code double} value corresponding to a given
845 * bit representation.
846 * The argument is considered to be a representation of a
847 * floating-point value according to the IEEE 754 floating-point
848 * "double format" bit layout.
849 *
850 * <p>If the argument is {@code 0x7ff0000000000000L}, the result
851 * is positive infinity.
852 *
853 * <p>If the argument is {@code 0xfff0000000000000L}, the result
854 * is negative infinity.
855 *
856 * <p>If the argument is any value in the range
857 * {@code 0x7ff0000000000001L} through
858 * {@code 0x7fffffffffffffffL} or in the range
859 * {@code 0xfff0000000000001L} through
860 * {@code 0xffffffffffffffffL}, the result is a NaN. No IEEE
861 * 754 floating-point operation provided by Java can distinguish
862 * between two NaN values of the same type with different bit
863 * patterns. Distinct values of NaN are only distinguishable by
864 * use of the {@code Double.doubleToRawLongBits} method.
865 *
866 * <p>In all other cases, let <i>s</i>, <i>e</i>, and <i>m</i> be three
867 * values that can be computed from the argument:
868 *
869 * <blockquote><pre>
870 * int s = ((bits >> 63) == 0) ? 1 : -1;
871 * int e = (int)((bits >> 52) & 0x7ffL);
872 * long m = (e == 0) ?
873 * (bits & 0xfffffffffffffL) << 1 :
874 * (bits & 0xfffffffffffffL) | 0x10000000000000L;
875 * </pre></blockquote>
876 *
877 * Then the floating-point result equals the value of the mathematical
878 * expression <i>s</i>·<i>m</i>·2<sup><i>e</i>-1075</sup>.
879 *
880 * <p>Note that this method may not be able to return a
881 * {@code double} NaN with exactly same bit pattern as the
882 * {@code long} argument. IEEE 754 distinguishes between two
883 * kinds of NaNs, quiet NaNs and <i>signaling NaNs</i>. The
884 * differences between the two kinds of NaN are generally not
885 * visible in Java. Arithmetic operations on signaling NaNs turn
886 * them into quiet NaNs with a different, but often similar, bit
887 * pattern. However, on some processors merely copying a
888 * signaling NaN also performs that conversion. In particular,
889 * copying a signaling NaN to return it to the calling method
890 * may perform this conversion. So {@code longBitsToDouble}
891 * may not be able to return a {@code double} with a
892 * signaling NaN bit pattern. Consequently, for some
893 * {@code long} values,
894 * {@code doubleToRawLongBits(longBitsToDouble(start))} may
895 * <i>not</i> equal {@code start}. Moreover, which
896 * particular bit patterns represent signaling NaNs is platform
897 * dependent; although all NaN bit patterns, quiet or signaling,
898 * must be in the NaN range identified above.
899 *
900 * @param bits any {@code long} integer.
901 * @return the {@code double} floating-point value with the same
902 * bit pattern.
903 */
904 public static native double longBitsToDouble(long bits);
905
906 /**
907 * Compares two {@code Double} objects numerically. There
908 * are two ways in which comparisons performed by this method
909 * differ from those performed by the Java language numerical
910 * comparison operators ({@code <, <=, ==, >=, >})
911 * when applied to primitive {@code double} values:
912 * <ul><li>
913 * {@code Double.NaN} is considered by this method
914 * to be equal to itself and greater than all other
915 * {@code double} values (including
916 * {@code Double.POSITIVE_INFINITY}).
917 * <li>
918 * {@code 0.0d} is considered by this method to be greater
919 * than {@code -0.0d}.
920 * </ul>
921 * This ensures that the <i>natural ordering</i> of
922 * {@code Double} objects imposed by this method is <i>consistent
923 * with equals</i>.
924 *
925 * @param anotherDouble the {@code Double} to be compared.
926 * @return the value {@code 0} if {@code anotherDouble} is
927 * numerically equal to this {@code Double}; a value
928 * less than {@code 0} if this {@code Double}
929 * is numerically less than {@code anotherDouble};
930 * and a value greater than {@code 0} if this
931 * {@code Double} is numerically greater than
932 * {@code anotherDouble}.
933 *
934 * @since 1.2
935 */
936 public int compareTo(Double anotherDouble) {
937 return Double.compare(value, anotherDouble.value);
938 }
939
940 /**
941 * Compares the two specified {@code double} values. The sign
942 * of the integer value returned is the same as that of the
943 * integer that would be returned by the call:
944 * <pre>
945 * new Double(d1).compareTo(new Double(d2))
946 * </pre>
947 *
948 * @param d1 the first {@code double} to compare
949 * @param d2 the second {@code double} to compare
950 * @return the value {@code 0} if {@code d1} is
951 * numerically equal to {@code d2}; a value less than
952 * {@code 0} if {@code d1} is numerically less than
953 * {@code d2}; and a value greater than {@code 0}
954 * if {@code d1} is numerically greater than
955 * {@code d2}.
956 * @since 1.4
957 */
958 public static int compare(double d1, double d2) {
959 if (d1 < d2)
960 return -1; // Neither val is NaN, thisVal is smaller
961 if (d1 > d2)
962 return 1; // Neither val is NaN, thisVal is larger
963
964 long this Bits = Double.doubleToLongBits(d1);
965 long anotherBits = Double.doubleToLongBits(d2);
966
967 return (this Bits == anotherBits ? 0 : // Values are equal
968 (this Bits < anotherBits ? -1 : // (-0.0, 0.0) or (!NaN, NaN)
969 1)); // (0.0, -0.0) or (NaN, !NaN)
970 }
971
972 /** use serialVersionUID from JDK 1.0.2 for interoperability */
973 private static final long serialVersionUID = -9172774392245257468L;
974 }
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