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25  
26  package java.lang;
27  
28  import sun.misc.FloatingDecimal;
29  import sun.misc.FpUtils;
30  import sun.misc.DoubleConsts;
31  
32  /**
33   * The {@code Double} class wraps a value of the primitive type
34   * {@code double} in an object. An object of type
35   * {@code Double} contains a single field whose type is
36   * {@code double}.
37   *
38   * <p>In addition, this class provides several methods for converting a
39   * {@code double} to a {@code String} and a
40   * {@code String} to a {@code double}, as well as other
41   * constants and methods useful when dealing with a
42   * {@code double}.
43   *
44   * @author  Lee Boynton
45   * @author  Arthur van Hoff
46   * @author  Joseph D. Darcy
47   * @since JDK1.0
48   */
49  public final class Double extends Number implements Comparable<Double> {
50      /**
51       * A constant holding the positive infinity of type
52       * {@code double}. It is equal to the value returned by
53       * {@code Double.longBitsToDouble(0x7ff0000000000000L)}.
54       */
55      public static final double POSITIVE_INFINITY = 1.0 / 0.0;
56  
57      /**
58       * A constant holding the negative infinity of type
59       * {@code double}. It is equal to the value returned by
60       * {@code Double.longBitsToDouble(0xfff0000000000000L)}.
61       */
62      public static final double NEGATIVE_INFINITY = -1.0 / 0.0;
63  
64      /**
65       * A constant holding a Not-a-Number (NaN) value of type
66       * {@code double}. It is equivalent to the value returned by
67       * {@code Double.longBitsToDouble(0x7ff8000000000000L)}.
68       */
69      public static final double NaN = 0.0d / 0.0;
70  
71      /**
72       * A constant holding the largest positive finite value of type
73       * {@code double},
74       * (2-2<sup>-52</sup>)&middot;2<sup>1023</sup>.  It is equal to
75       * the hexadecimal floating-point literal
76       * {@code 0x1.fffffffffffffP+1023} and also equal to
77       * {@code Double.longBitsToDouble(0x7fefffffffffffffL)}.
78       */
79      public static final double MAX_VALUE = 0x1.fffffffffffffP+1023; // 1.7976931348623157e+308
80  
81      /**
82       * A constant holding the smallest positive normal value of type
83       * {@code double}, 2<sup>-1022</sup>.  It is equal to the
84       * hexadecimal floating-point literal {@code 0x1.0p-1022} and also
85       * equal to {@code Double.longBitsToDouble(0x0010000000000000L)}.
86       *
87       * @since 1.6
88       */
89      public static final double MIN_NORMAL = 0x1.0p-1022; // 2.2250738585072014E-308
90  
91      /**
92       * A constant holding the smallest positive nonzero value of type
93       * {@code double}, 2<sup>-1074</sup>. It is equal to the
94       * hexadecimal floating-point literal
95       * {@code 0x0.0000000000001P-1022} and also equal to
96       * {@code Double.longBitsToDouble(0x1L)}.
97       */
98      public static final double MIN_VALUE = 0x0.0000000000001P-1022; // 4.9e-324
99  
100     /**
101      * Maximum exponent a finite {@code double} variable may have.
102      * It is equal to the value returned by
103      * {@code Math.getExponent(Double.MAX_VALUE)}.
104      *
105      * @since 1.6
106      */
107     public static final int MAX_EXPONENT = 1023;
108 
109     /**
110      * Minimum exponent a normalized {@code double} variable may
111      * have.  It is equal to the value returned by
112      * {@code Math.getExponent(Double.MIN_NORMAL)}.
113      *
114      * @since 1.6
115      */
116     public static final int MIN_EXPONENT = -1022;
117 
118     /**
119      * The number of bits used to represent a {@code double} value.
120      *
121      * @since 1.5
122      */
123     public static final int SIZE = 64;
124 
125     /**
126      * The number of bytes used to represent a {@code double} value.
127      *
128      * @since 1.8
129      */
130     public static final int BYTES = SIZE / Byte.SIZE;
131 
132     /**
133      * The {@code Class} instance representing the primitive type
134      * {@code double}.
135      *
136      * @since JDK1.1
137      */
138     @SuppressWarnings("unchecked")
139     public static final Class<Double>   TYPE = (Class<Double>) Class.getPrimitiveClass("double");
140 
141     /**
142      * Returns a string representation of the {@code double}
143      * argument. All characters mentioned below are ASCII characters.
144      * <ul>
145      * <li>If the argument is NaN, the result is the string
146      *     "{@code NaN}".
147      * <li>Otherwise, the result is a string that represents the sign and
148      * magnitude (absolute value) of the argument. If the sign is negative,
149      * the first character of the result is '{@code -}'
150      * ({@code '\u005Cu002D'}); if the sign is positive, no sign character
151      * appears in the result. As for the magnitude <i>m</i>:
152      * <ul>
153      * <li>If <i>m</i> is infinity, it is represented by the characters
154      * {@code "Infinity"}; thus, positive infinity produces the result
155      * {@code "Infinity"} and negative infinity produces the result
156      * {@code "-Infinity"}.
157      *
158      * <li>If <i>m</i> is zero, it is represented by the characters
159      * {@code "0.0"}; thus, negative zero produces the result
160      * {@code "-0.0"} and positive zero produces the result
161      * {@code "0.0"}.
162      *
163      * <li>If <i>m</i> is greater than or equal to 10<sup>-3</sup> but less
164      * than 10<sup>7</sup>, then it is represented as the integer part of
165      * <i>m</i>, in decimal form with no leading zeroes, followed by
166      * '{@code .}' ({@code '\u005Cu002E'}), followed by one or
167      * more decimal digits representing the fractional part of <i>m</i>.
168      *
169      * <li>If <i>m</i> is less than 10<sup>-3</sup> or greater than or
170      * equal to 10<sup>7</sup>, then it is represented in so-called
171      * "computerized scientific notation." Let <i>n</i> be the unique
172      * integer such that 10<sup><i>n</i></sup> &le; <i>m</i> {@literal <}
173      * 10<sup><i>n</i>+1</sup>; then let <i>a</i> be the
174      * mathematically exact quotient of <i>m</i> and
175      * 10<sup><i>n</i></sup> so that 1 &le; <i>a</i> {@literal <} 10. The
176      * magnitude is then represented as the integer part of <i>a</i>,
177      * as a single decimal digit, followed by '{@code .}'
178      * ({@code '\u005Cu002E'}), followed by decimal digits
179      * representing the fractional part of <i>a</i>, followed by the
180      * letter '{@code E}' ({@code '\u005Cu0045'}), followed
181      * by a representation of <i>n</i> as a decimal integer, as
182      * produced by the method {@link Integer#toString(int)}.
183      * </ul>
184      * </ul>
185      * How many digits must be printed for the fractional part of
186      * <i>m</i> or <i>a</i>? There must be at least one digit to represent
187      * the fractional part, and beyond that as many, but only as many, more
188      * digits as are needed to uniquely distinguish the argument value from
189      * adjacent values of type {@code double}. That is, suppose that
190      * <i>x</i> is the exact mathematical value represented by the decimal
191      * representation produced by this method for a finite nonzero argument
192      * <i>d</i>. Then <i>d</i> must be the {@code double} value nearest
193      * to <i>x</i>; or if two {@code double} values are equally close
194      * to <i>x</i>, then <i>d</i> must be one of them and the least
195      * significant bit of the significand of <i>d</i> must be {@code 0}.
196      *
197      * <p>To create localized string representations of a floating-point
198      * value, use subclasses of {@link java.text.NumberFormat}.
199      *
200      * @param   d   the {@code double} to be converted.
201      * @return a string representation of the argument.
202      */
203     public static String toString(double d) {
204         return FloatingDecimal.toJavaFormatString(d);
205     }
206 
207     /**
208      * Returns a hexadecimal string representation of the
209      * {@code double} argument. All characters mentioned below
210      * are ASCII characters.
211      *
212      * <ul>
213      * <li>If the argument is NaN, the result is the string
214      *     "{@code NaN}".
215      * <li>Otherwise, the result is a string that represents the sign
216      * and magnitude of the argument. If the sign is negative, the
217      * first character of the result is '{@code -}'
218      * ({@code '\u005Cu002D'}); if the sign is positive, no sign
219      * character appears in the result. As for the magnitude <i>m</i>:
220      *
221      * <ul>
222      * <li>If <i>m</i> is infinity, it is represented by the string
223      * {@code "Infinity"}; thus, positive infinity produces the
224      * result {@code "Infinity"} and negative infinity produces
225      * the result {@code "-Infinity"}.
226      *
227      * <li>If <i>m</i> is zero, it is represented by the string
228      * {@code "0x0.0p0"}; thus, negative zero produces the result
229      * {@code "-0x0.0p0"} and positive zero produces the result
230      * {@code "0x0.0p0"}.
231      *
232      * <li>If <i>m</i> is a {@code double} value with a
233      * normalized representation, substrings are used to represent the
234      * significand and exponent fields.  The significand is
235      * represented by the characters {@code "0x1."}
236      * followed by a lowercase hexadecimal representation of the rest
237      * of the significand as a fraction.  Trailing zeros in the
238      * hexadecimal representation are removed unless all the digits
239      * are zero, in which case a single zero is used. Next, the
240      * exponent is represented by {@code "p"} followed
241      * by a decimal string of the unbiased exponent as if produced by
242      * a call to {@link Integer#toString(int) Integer.toString} on the
243      * exponent value.
244      *
245      * <li>If <i>m</i> is a {@code double} value with a subnormal
246      * representation, the significand is represented by the
247      * characters {@code "0x0."} followed by a
248      * hexadecimal representation of the rest of the significand as a
249      * fraction.  Trailing zeros in the hexadecimal representation are
250      * removed. Next, the exponent is represented by
251      * {@code "p-1022"}.  Note that there must be at
252      * least one nonzero digit in a subnormal significand.
253      *
254      * </ul>
255      *
256      * </ul>
257      *
258      * <table border>
259      * <caption>Examples</caption>
260      * <tr><th>Floating-point Value</th><th>Hexadecimal String</th>
261      * <tr><td>{@code 1.0}</td> <td>{@code 0x1.0p0}</td>
262      * <tr><td>{@code -1.0}</td>        <td>{@code -0x1.0p0}</td>
263      * <tr><td>{@code 2.0}</td> <td>{@code 0x1.0p1}</td>
264      * <tr><td>{@code 3.0}</td> <td>{@code 0x1.8p1}</td>
265      * <tr><td>{@code 0.5}</td> <td>{@code 0x1.0p-1}</td>
266      * <tr><td>{@code 0.25}</td>        <td>{@code 0x1.0p-2}</td>
267      * <tr><td>{@code Double.MAX_VALUE}</td>
268      *     <td>{@code 0x1.fffffffffffffp1023}</td>
269      * <tr><td>{@code Minimum Normal Value}</td>
270      *     <td>{@code 0x1.0p-1022}</td>
271      * <tr><td>{@code Maximum Subnormal Value}</td>
272      *     <td>{@code 0x0.fffffffffffffp-1022}</td>
273      * <tr><td>{@code Double.MIN_VALUE}</td>
274      *     <td>{@code 0x0.0000000000001p-1022}</td>
275      * </table>
276      * @param   d   the {@code double} to be converted.
277      * @return a hex string representation of the argument.
278      * @since 1.5
279      * @author Joseph D. Darcy
280      */
281     public static String toHexString(double d) {
282         /*
283          * Modeled after the "a" conversion specifier in C99, section
284          * 7.19.6.1; however, the output of this method is more
285          * tightly specified.
286          */
287         if (!isFinite(d) )
288             // For infinity and NaN, use the decimal output.
289             return Double.toString(d);
290         else {
291             // Initialized to maximum size of output.
292             StringBuilder answer = new StringBuilder(24);
293 
294             if (Math.copySign(1.0, d) == -1.0)    // value is negative,
295                 answer.append("-");                  // so append sign info
296 
297             answer.append("0x");
298 
299             d = Math.abs(d);
300 
301             if(d == 0.0) {
302                 answer.append("0.0p0");
303             } else {
304                 boolean subnormal = (d < DoubleConsts.MIN_NORMAL);
305 
306                 // Isolate significand bits and OR in a high-order bit
307                 // so that the string representation has a known
308                 // length.
309                 long signifBits = (Double.doubleToLongBits(d)
310                                    & DoubleConsts.SIGNIF_BIT_MASK) |
311                     0x1000000000000000L;
312 
313                 // Subnormal values have a 0 implicit bit; normal
314                 // values have a 1 implicit bit.
315                 answer.append(subnormal ? "0." : "1.");
316 
317                 // Isolate the low-order 13 digits of the hex
318                 // representation.  If all the digits are zero,
319                 // replace with a single 0; otherwise, remove all
320                 // trailing zeros.
321                 String signif = Long.toHexString(signifBits).substring(3,16);
322                 answer.append(signif.equals("0000000000000") ? // 13 zeros
323                               "0":
324                               signif.replaceFirst("0{1,12}$", ""));
325 
326                 answer.append('p');
327                 // If the value is subnormal, use the E_min exponent
328                 // value for double; otherwise, extract and report d's
329                 // exponent (the representation of a subnormal uses
330                 // E_min -1).
331                 answer.append(subnormal ?
332                               DoubleConsts.MIN_EXPONENT:
333                               Math.getExponent(d));
334             }
335             return answer.toString();
336         }
337     }
338 
339     /**
340      * Returns a {@code Double} object holding the
341      * {@code double} value represented by the argument string
342      * {@code s}.
343      *
344      * <p>If {@code s} is {@code null}, then a
345      * {@code NullPointerException} is thrown.
346      *
347      * <p>Leading and trailing whitespace characters in {@code s}
348      * are ignored.  Whitespace is removed as if by the {@link
349      * String#trim} method; that is, both ASCII space and control
350      * characters are removed. The rest of {@code s} should
351      * constitute a <i>FloatValue</i> as described by the lexical
352      * syntax rules:
353      *
354      * <blockquote>
355      * <dl>
356      * <dt><i>FloatValue:</i>
357      * <dd><i>Sign<sub>opt</sub></i> {@code NaN}
358      * <dd><i>Sign<sub>opt</sub></i> {@code Infinity}
359      * <dd><i>Sign<sub>opt</sub> FloatingPointLiteral</i>
360      * <dd><i>Sign<sub>opt</sub> HexFloatingPointLiteral</i>
361      * <dd><i>SignedInteger</i>
362      * </dl>
363      *
364      * <dl>
365      * <dt><i>HexFloatingPointLiteral</i>:
366      * <dd> <i>HexSignificand BinaryExponent FloatTypeSuffix<sub>opt</sub></i>
367      * </dl>
368      *
369      * <dl>
370      * <dt><i>HexSignificand:</i>
371      * <dd><i>HexNumeral</i>
372      * <dd><i>HexNumeral</i> {@code .}
373      * <dd>{@code 0x} <i>HexDigits<sub>opt</sub>
374      *     </i>{@code .}<i> HexDigits</i>
375      * <dd>{@code 0X}<i> HexDigits<sub>opt</sub>
376      *     </i>{@code .} <i>HexDigits</i>
377      * </dl>
378      *
379      * <dl>
380      * <dt><i>BinaryExponent:</i>
381      * <dd><i>BinaryExponentIndicator SignedInteger</i>
382      * </dl>
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
396      * <cite>The Java&trade; Language Specification</cite>,
397      * except that underscores are not accepted between digits.
398      * If {@code s} does not have the form of
399      * a <i>FloatValue</i>, then a {@code NumberFormatException}
400      * is thrown. Otherwise, {@code s} is regarded as
401      * representing an exact decimal value in the usual
402      * "computerized scientific notation" or as an exact
403      * hexadecimal value; this exact numerical value is then
404      * conceptually converted to an "infinitely precise"
405      * binary value that is then rounded to type {@code double}
406      * by the usual round-to-nearest rule of IEEE 754 floating-point
407      * arithmetic, which includes preserving the sign of a zero
408      * value.
409      *
410      * Note that the round-to-nearest rule also implies overflow and
411      * underflow behaviour; if the exact value of {@code s} is large
412      * enough in magnitude (greater than or equal to ({@link
413      * #MAX_VALUE} + {@link Math#ulp(double) ulp(MAX_VALUE)}/2),
414      * rounding to {@code double} will result in an infinity and if the
415      * exact value of {@code s} is small enough in magnitude (less
416      * than or equal to {@link #MIN_VALUE}/2), rounding to float will
417      * result in a zero.
418      *
419      * Finally, after rounding a {@code Double} object representing
420      * this {@code double} value is returned.
421      *
422      * <p> To interpret localized string representations of a
423      * floating-point value, use subclasses of {@link
424      * java.text.NumberFormat}.
425      *
426      * <p>Note that trailing format specifiers, specifiers that
427      * determine the type of a floating-point literal
428      * ({@code 1.0f} is a {@code float} value;
429      * {@code 1.0d} is a {@code double} value), do
430      * <em>not</em> influence the results of this method.  In other
431      * words, the numerical value of the input string is converted
432      * directly to the target floating-point type.  The two-step
433      * sequence of conversions, string to {@code float} followed
434      * by {@code float} to {@code double}, is <em>not</em>
435      * equivalent to converting a string directly to
436      * {@code double}. For example, the {@code float}
437      * literal {@code 0.1f} is equal to the {@code double}
438      * value {@code 0.10000000149011612}; the {@code float}
439      * literal {@code 0.1f} represents a different numerical
440      * value than the {@code double} literal
441      * {@code 0.1}. (The numerical value 0.1 cannot be exactly
442      * represented in a binary floating-point number.)
443      *
444      * <p>To avoid calling this method on an invalid string and having
445      * a {@code NumberFormatException} be thrown, the regular
446      * expression below can be used to screen the input string:
447      *
448      * <pre>{@code
449      *  final String Digits     = "(\\p{Digit}+)";
450      *  final String HexDigits  = "(\\p{XDigit}+)";
451      *  // an exponent is 'e' or 'E' followed by an optionally
452      *  // signed decimal integer.
453      *  final String Exp        = "[eE][+-]?"+Digits;
454      *  final String fpRegex    =
455      *      ("[\\x00-\\x20]*"+  // Optional leading "whitespace"
456      *       "[+-]?(" + // Optional sign character
457      *       "NaN|" +           // "NaN" string
458      *       "Infinity|" +      // "Infinity" string
459      *
460      *       // A decimal floating-point string representing a finite positive
461      *       // number without a leading sign has at most five basic pieces:
462      *       // Digits . Digits ExponentPart FloatTypeSuffix
463      *       //
464      *       // Since this method allows integer-only strings as input
465      *       // in addition to strings of floating-point literals, the
466      *       // two sub-patterns below are simplifications of the grammar
467      *       // productions from section 3.10.2 of
468      *       // The Java Language Specification.
469      *
470      *       // Digits ._opt Digits_opt ExponentPart_opt FloatTypeSuffix_opt
471      *       "((("+Digits+"(\\.)?("+Digits+"?)("+Exp+")?)|"+
472      *
473      *       // . Digits ExponentPart_opt FloatTypeSuffix_opt
474      *       "(\\.("+Digits+")("+Exp+")?)|"+
475      *
476      *       // Hexadecimal strings
477      *       "((" +
478      *        // 0[xX] HexDigits ._opt BinaryExponent FloatTypeSuffix_opt
479      *        "(0[xX]" + HexDigits + "(\\.)?)|" +
480      *
481      *        // 0[xX] HexDigits_opt . HexDigits BinaryExponent FloatTypeSuffix_opt
482      *        "(0[xX]" + HexDigits + "?(\\.)" + HexDigits + ")" +
483      *
484      *        ")[pP][+-]?" + Digits + "))" +
485      *       "[fFdD]?))" +
486      *       "[\\x00-\\x20]*");// Optional trailing "whitespace"
487      *
488      *  if (Pattern.matches(fpRegex, myString))
489      *      Double.valueOf(myString); // Will not throw NumberFormatException
490      *  else {
491      *      // Perform suitable alternative action
492      *  }
493      * }</pre>
494      *
495      * @param      s   the string to be parsed.
496      * @return     a {@code Double} object holding the value
497      *             represented by the {@code String} argument.
498      * @throws     NumberFormatException  if the string does not contain a
499      *             parsable number.
500      */
501     public static Double valueOf(String s) throws NumberFormatException {
502         return new Double(parseDouble(s));
503     }
504 
505     /**
506      * Returns a {@code Double} instance representing the specified
507      * {@code double} value.
508      * If a new {@code Double} instance is not required, this method
509      * should generally be used in preference to the constructor
510      * {@link #Double(double)}, as this method is likely to yield
511      * significantly better space and time performance by caching
512      * frequently requested values.
513      *
514      * @param  d a double value.
515      * @return a {@code Double} instance representing {@code d}.
516      * @since  1.5
517      */
518     public static Double valueOf(double d) {
519         return new Double(d);
520     }
521 
522     /**
523      * Returns a new {@code double} initialized to the value
524      * represented by the specified {@code String}, as performed
525      * by the {@code valueOf} method of class
526      * {@code Double}.
527      *
528      * @param  s   the string to be parsed.
529      * @return the {@code double} value represented by the string
530      *         argument.
531      * @throws NullPointerException  if the string is null
532      * @throws NumberFormatException if the string does not contain
533      *         a parsable {@code double}.
534      * @see    java.lang.Double#valueOf(String)
535      * @since 1.2
536      */
537     public static double parseDouble(String s) throws NumberFormatException {
538         return FloatingDecimal.parseDouble(s);
539     }
540 
541     /**
542      * Returns {@code true} if the specified number is a
543      * Not-a-Number (NaN) value, {@code false} otherwise.
544      *
545      * @param   v   the value to be tested.
546      * @return  {@code true} if the value of the argument is NaN;
547      *          {@code false} otherwise.
548      */
549     public static boolean isNaN(double v) {
550         return (v != v);
551     }
552 
553     /**
554      * Returns {@code true} if the specified number is infinitely
555      * large in magnitude, {@code false} otherwise.
556      *
557      * @param   v   the value to be tested.
558      * @return  {@code true} if the value of the argument is positive
559      *          infinity or negative infinity; {@code false} otherwise.
560      */
561     public static boolean isInfinite(double v) {
562         return (v == POSITIVE_INFINITY) || (v == NEGATIVE_INFINITY);
563     }
564 
565     /**
566      * Returns {@code true} if the argument is a finite floating-point
567      * value; returns {@code false} otherwise (for NaN and infinity
568      * arguments).
569      *
570      * @param d the {@code double} value to be tested
571      * @return {@code true} if the argument is a finite
572      * floating-point value, {@code false} otherwise.
573      * @since 1.8
574      */
575     public static boolean isFinite(double d) {
576         return Math.abs(d) <= DoubleConsts.MAX_VALUE;
577     }
578 
579     /**
580      * The value of the Double.
581      *
582      * @serial
583      */
584     private final double value;
585 
586     /**
587      * Constructs a newly allocated {@code Double} object that
588      * represents the primitive {@code double} argument.
589      *
590      * @param   value   the value to be represented by the {@code Double}.
591      */
592     public Double(double value) {
593         this.value = value;
594     }
595 
596     /**
597      * Constructs a newly allocated {@code Double} object that
598      * represents the floating-point value of type {@code double}
599      * represented by the string. The string is converted to a
600      * {@code double} value as if by the {@code valueOf} method.
601      *
602      * @param  s  a string to be converted to a {@code Double}.
603      * @throws    NumberFormatException  if the string does not contain a
604      *            parsable number.
605      * @see       java.lang.Double#valueOf(java.lang.String)
606      */
607     public Double(String s) throws NumberFormatException {
608         value = parseDouble(s);
609     }
610 
611     /**
612      * Returns {@code true} if this {@code Double} value is
613      * a Not-a-Number (NaN), {@code false} otherwise.
614      *
615      * @return  {@code true} if the value represented by this object is
616      *          NaN; {@code false} otherwise.
617      */
618     public boolean isNaN() {
619         return isNaN(value);
620     }
621 
622     /**
623      * Returns {@code true} if this {@code Double} value is
624      * infinitely large in magnitude, {@code false} otherwise.
625      *
626      * @return  {@code true} if the value represented by this object is
627      *          positive infinity or negative infinity;
628      *          {@code false} otherwise.
629      */
630     public boolean isInfinite() {
631         return isInfinite(value);
632     }
633 
634     /**
635      * Returns a string representation of this {@code Double} object.
636      * The primitive {@code double} value represented by this
637      * object is converted to a string exactly as if by the method
638      * {@code toString} of one argument.
639      *
640      * @return  a {@code String} representation of this object.
641      * @see java.lang.Double#toString(double)
642      */
643     public String toString() {
644         return toString(value);
645     }
646 
647     /**
648      * Returns the value of this {@code Double} as a {@code byte}
649      * after a narrowing primitive conversion.
650      *
651      * @return  the {@code double} value represented by this object
652      *          converted to type {@code byte}
653      * @jls 5.1.3 Narrowing Primitive Conversions
654      * @since JDK1.1
655      */
656     public byte byteValue() {
657         return (byte)value;
658     }
659 
660     /**
661      * Returns the value of this {@code Double} as a {@code short}
662      * after a narrowing primitive conversion.
663      *
664      * @return  the {@code double} value represented by this object
665      *          converted to type {@code short}
666      * @jls 5.1.3 Narrowing Primitive Conversions
667      * @since JDK1.1
668      */
669     public short shortValue() {
670         return (short)value;
671     }
672 
673     /**
674      * Returns the value of this {@code Double} as an {@code int}
675      * after a narrowing primitive conversion.
676      * @jls 5.1.3 Narrowing Primitive Conversions
677      *
678      * @return  the {@code double} value represented by this object
679      *          converted to type {@code int}
680      */
681     public int intValue() {
682         return (int)value;
683     }
684 
685     /**
686      * Returns the value of this {@code Double} as a {@code long}
687      * after a narrowing primitive conversion.
688      *
689      * @return  the {@code double} value represented by this object
690      *          converted to type {@code long}
691      * @jls 5.1.3 Narrowing Primitive Conversions
692      */
693     public long longValue() {
694         return (long)value;
695     }
696 
697     /**
698      * Returns the value of this {@code Double} as a {@code float}
699      * after a narrowing primitive conversion.
700      *
701      * @return  the {@code double} value represented by this object
702      *          converted to type {@code float}
703      * @jls 5.1.3 Narrowing Primitive Conversions
704      * @since JDK1.0
705      */
706     public float floatValue() {
707         return (float)value;
708     }
709 
710     /**
711      * Returns the {@code double} value of this {@code Double} object.
712      *
713      * @return the {@code double} value represented by this object
714      */
715     public double doubleValue() {
716         return value;
717     }
718 
719     /**
720      * Returns a hash code for this {@code Double} object. The
721      * result is the exclusive OR of the two halves of the
722      * {@code long} integer bit representation, exactly as
723      * produced by the method {@link #doubleToLongBits(double)}, of
724      * the primitive {@code double} value represented by this
725      * {@code Double} object. That is, the hash code is the value
726      * of the expression:
727      *
728      * <blockquote>
729      *  {@code (int)(v^(v>>>32))}
730      * </blockquote>
731      *
732      * where {@code v} is defined by:
733      *
734      * <blockquote>
735      *  {@code long v = Double.doubleToLongBits(this.doubleValue());}
736      * </blockquote>
737      *
738      * @return  a {@code hash code} value for this object.
739      */
740     @Override
741     public int hashCode() {
742         return Double.hashCode(value);
743     }
744 
745     /**
746      * Returns a hash code for a {@code double} value; compatible with
747      * {@code Double.hashCode()}.
748      *
749      * @param value the value to hash
750      * @return a hash code value for a {@code double} value.
751      * @since 1.8
752      */
753     public static int hashCode(double value) {
754         long bits = doubleToLongBits(value);
755         return (int)(bits ^ (bits >>> 32));
756     }
757 
758     /**
759      * Compares this object against the specified object.  The result
760      * is {@code true} if and only if the argument is not
761      * {@code null} and is a {@code Double} object that
762      * represents a {@code double} that has the same value as the
763      * {@code double} represented by this object. For this
764      * purpose, two {@code double} values are considered to be
765      * the same if and only if the method {@link
766      * #doubleToLongBits(double)} returns the identical
767      * {@code long} value when applied to each.
768      *
769      * <p>Note that in most cases, for two instances of class
770      * {@code Double}, {@code d1} and {@code d2}, the
771      * value of {@code d1.equals(d2)} is {@code true} if and
772      * only if
773      *
774      * <blockquote>
775      *  {@code d1.doubleValue() == d2.doubleValue()}
776      * </blockquote>
777      *
778      * <p>also has the value {@code true}. However, there are two
779      * exceptions:
780      * <ul>
781      * <li>If {@code d1} and {@code d2} both represent
782      *     {@code Double.NaN}, then the {@code equals} method
783      *     returns {@code true}, even though
784      *     {@code Double.NaN==Double.NaN} has the value
785      *     {@code false}.
786      * <li>If {@code d1} represents {@code +0.0} while
787      *     {@code d2} represents {@code -0.0}, or vice versa,
788      *     the {@code equal} test has the value {@code false},
789      *     even though {@code +0.0==-0.0} has the value {@code true}.
790      * </ul>
791      * This definition allows hash tables to operate properly.
792      * @param   obj   the object to compare with.
793      * @return  {@code true} if the objects are the same;
794      *          {@code false} otherwise.
795      * @see java.lang.Double#doubleToLongBits(double)
796      */
797     public boolean equals(Object obj) {
798         return (obj instanceof Double)
799                && (doubleToLongBits(((Double)obj).value) ==
800                       doubleToLongBits(value));
801     }
802 
803     /**
804      * Returns a representation of the specified floating-point value
805      * according to the IEEE 754 floating-point "double
806      * format" bit layout.
807      *
808      * <p>Bit 63 (the bit that is selected by the mask
809      * {@code 0x8000000000000000L}) represents the sign of the
810      * floating-point number. Bits
811      * 62-52 (the bits that are selected by the mask
812      * {@code 0x7ff0000000000000L}) represent the exponent. Bits 51-0
813      * (the bits that are selected by the mask
814      * {@code 0x000fffffffffffffL}) represent the significand
815      * (sometimes called the mantissa) of the floating-point number.
816      *
817      * <p>If the argument is positive infinity, the result is
818      * {@code 0x7ff0000000000000L}.
819      *
820      * <p>If the argument is negative infinity, the result is
821      * {@code 0xfff0000000000000L}.
822      *
823      * <p>If the argument is NaN, the result is
824      * {@code 0x7ff8000000000000L}.
825      *
826      * <p>In all cases, the result is a {@code long} integer that, when
827      * given to the {@link #longBitsToDouble(long)} method, will produce a
828      * floating-point value the same as the argument to
829      * {@code doubleToLongBits} (except all NaN values are
830      * collapsed to a single "canonical" NaN value).
831      *
832      * @param   value   a {@code double} precision floating-point number.
833      * @return the bits that represent the floating-point number.
834      */
835     public static long doubleToLongBits(double value) {
836         long result = doubleToRawLongBits(value);
837         // Check for NaN based on values of bit fields, maximum
838         // exponent and nonzero significand.
839         if ( ((result & DoubleConsts.EXP_BIT_MASK) ==
840               DoubleConsts.EXP_BIT_MASK) &&
841              (result & DoubleConsts.SIGNIF_BIT_MASK) != 0L)
842             result = 0x7ff8000000000000L;
843         return result;
844     }
845 
846     /**
847      * Returns a representation of the specified floating-point value
848      * according to the IEEE 754 floating-point "double
849      * format" bit layout, preserving Not-a-Number (NaN) values.
850      *
851      * <p>Bit 63 (the bit that is selected by the mask
852      * {@code 0x8000000000000000L}) represents the sign of the
853      * floating-point number. Bits
854      * 62-52 (the bits that are selected by the mask
855      * {@code 0x7ff0000000000000L}) represent the exponent. Bits 51-0
856      * (the bits that are selected by the mask
857      * {@code 0x000fffffffffffffL}) represent the significand
858      * (sometimes called the mantissa) of the floating-point number.
859      *
860      * <p>If the argument is positive infinity, the result is
861      * {@code 0x7ff0000000000000L}.
862      *
863      * <p>If the argument is negative infinity, the result is
864      * {@code 0xfff0000000000000L}.
865      *
866      * <p>If the argument is NaN, the result is the {@code long}
867      * integer representing the actual NaN value.  Unlike the
868      * {@code doubleToLongBits} method,
869      * {@code doubleToRawLongBits} does not collapse all the bit
870      * patterns encoding a NaN to a single "canonical" NaN
871      * value.
872      *
873      * <p>In all cases, the result is a {@code long} integer that,
874      * when given to the {@link #longBitsToDouble(long)} method, will
875      * produce a floating-point value the same as the argument to
876      * {@code doubleToRawLongBits}.
877      *
878      * @param   value   a {@code double} precision floating-point number.
879      * @return the bits that represent the floating-point number.
880      * @since 1.3
881      */
882     public static native long doubleToRawLongBits(double value);
883 
884     /**
885      * Returns the {@code double} value corresponding to a given
886      * bit representation.
887      * The argument is considered to be a representation of a
888      * floating-point value according to the IEEE 754 floating-point
889      * "double format" bit layout.
890      *
891      * <p>If the argument is {@code 0x7ff0000000000000L}, the result
892      * is positive infinity.
893      *
894      * <p>If the argument is {@code 0xfff0000000000000L}, the result
895      * is negative infinity.
896      *
897      * <p>If the argument is any value in the range
898      * {@code 0x7ff0000000000001L} through
899      * {@code 0x7fffffffffffffffL} or in the range
900      * {@code 0xfff0000000000001L} through
901      * {@code 0xffffffffffffffffL}, the result is a NaN.  No IEEE
902      * 754 floating-point operation provided by Java can distinguish
903      * between two NaN values of the same type with different bit
904      * patterns.  Distinct values of NaN are only distinguishable by
905      * use of the {@code Double.doubleToRawLongBits} method.
906      *
907      * <p>In all other cases, let <i>s</i>, <i>e</i>, and <i>m</i> be three
908      * values that can be computed from the argument:
909      *
910      * <blockquote><pre>{@code
911      * int s = ((bits >> 63) == 0) ? 1 : -1;
912      * int e = (int)((bits >> 52) & 0x7ffL);
913      * long m = (e == 0) ?
914      *                 (bits & 0xfffffffffffffL) << 1 :
915      *                 (bits & 0xfffffffffffffL) | 0x10000000000000L;
916      * }</pre></blockquote>
917      *
918      * Then the floating-point result equals the value of the mathematical
919      * expression <i>s</i>&middot;<i>m</i>&middot;2<sup><i>e</i>-1075</sup>.
920      *
921      * <p>Note that this method may not be able to return a
922      * {@code double} NaN with exactly same bit pattern as the
923      * {@code long} argument.  IEEE 754 distinguishes between two
924      * kinds of NaNs, quiet NaNs and <i>signaling NaNs</i>.  The
925      * differences between the two kinds of NaN are generally not
926      * visible in Java.  Arithmetic operations on signaling NaNs turn
927      * them into quiet NaNs with a different, but often similar, bit
928      * pattern.  However, on some processors merely copying a
929      * signaling NaN also performs that conversion.  In particular,
930      * copying a signaling NaN to return it to the calling method
931      * may perform this conversion.  So {@code longBitsToDouble}
932      * may not be able to return a {@code double} with a
933      * signaling NaN bit pattern.  Consequently, for some
934      * {@code long} values,
935      * {@code doubleToRawLongBits(longBitsToDouble(start))} may
936      * <i>not</i> equal {@code start}.  Moreover, which
937      * particular bit patterns represent signaling NaNs is platform
938      * dependent; although all NaN bit patterns, quiet or signaling,
939      * must be in the NaN range identified above.
940      *
941      * @param   bits   any {@code long} integer.
942      * @return  the {@code double} floating-point value with the same
943      *          bit pattern.
944      */
945     public static native double longBitsToDouble(long bits);
946 
947     /**
948      * Compares two {@code Double} objects numerically.  There
949      * are two ways in which comparisons performed by this method
950      * differ from those performed by the Java language numerical
951      * comparison operators ({@code <, <=, ==, >=, >})
952      * when applied to primitive {@code double} values:
953      * <ul><li>
954      *          {@code Double.NaN} is considered by this method
955      *          to be equal to itself and greater than all other
956      *          {@code double} values (including
957      *          {@code Double.POSITIVE_INFINITY}).
958      * <li>
959      *          {@code 0.0d} is considered by this method to be greater
960      *          than {@code -0.0d}.
961      * </ul>
962      * This ensures that the <i>natural ordering</i> of
963      * {@code Double} objects imposed by this method is <i>consistent
964      * with equals</i>.
965      *
966      * @param   anotherDouble   the {@code Double} to be compared.
967      * @return  the value {@code 0} if {@code anotherDouble} is
968      *          numerically equal to this {@code Double}; a value
969      *          less than {@code 0} if this {@code Double}
970      *          is numerically less than {@code anotherDouble};
971      *          and a value greater than {@code 0} if this
972      *          {@code Double} is numerically greater than
973      *          {@code anotherDouble}.
974      *
975      * @since   1.2
976      */
977     public int compareTo(Double anotherDouble) {
978         return Double.compare(value, anotherDouble.value);
979     }
980 
981     /**
982      * Compares the two specified {@code double} values. The sign
983      * of the integer value returned is the same as that of the
984      * integer that would be returned by the call:
985      * <pre>
986      *    new Double(d1).compareTo(new Double(d2))
987      * </pre>
988      *
989      * @param   d1        the first {@code double} to compare
990      * @param   d2        the second {@code double} to compare
991      * @return  the value {@code 0} if {@code d1} is
992      *          numerically equal to {@code d2}; a value less than
993      *          {@code 0} if {@code d1} is numerically less than
994      *          {@code d2}; and a value greater than {@code 0}
995      *          if {@code d1} is numerically greater than
996      *          {@code d2}.
997      * @since 1.4
998      */
999     public static int compare(double d1, double d2) {
1000         if (d1 < d2)
1001             return -1;           // Neither val is NaN, thisVal is smaller
1002         if (d1 > d2)
1003             return 1;            // Neither val is NaN, thisVal is larger
1004 
1005         // Cannot use doubleToRawLongBits because of possibility of NaNs.
1006         long thisBits    = Double.doubleToLongBits(d1);
1007         long anotherBits = Double.doubleToLongBits(d2);
1008 
1009         return (thisBits == anotherBits ?  0 : // Values are equal
1010                 (thisBits < anotherBits ? -1 : // (-0.0, 0.0) or (!NaN, NaN)
1011                  1));                          // (0.0, -0.0) or (NaN, !NaN)
1012     }
1013 
1014     /**
1015      * Adds two {@code double} values together as per the + operator.
1016      *
1017      * @param a the first operand
1018      * @param b the second operand
1019      * @return the sum of {@code a} and {@code b}
1020      * @jls 4.2.4 Floating-Point Operations
1021      * @see java.util.function.BinaryOperator
1022      * @since 1.8
1023      */
1024     public static double sum(double a, double b) {
1025         return a + b;
1026     }
1027 
1028     /**
1029      * Returns the greater of two {@code double} values
1030      * as if by calling {@link Math#max(double, double) Math.max}.
1031      *
1032      * @param a the first operand
1033      * @param b the second operand
1034      * @return the greater of {@code a} and {@code b}
1035      * @see java.util.function.BinaryOperator
1036      * @since 1.8
1037      */
1038     public static double max(double a, double b) {
1039         return Math.max(a, b);
1040     }
1041 
1042     /**
1043      * Returns the smaller of two {@code double} values
1044      * as if by calling {@link Math#min(double, double) Math.min}.
1045      *
1046      * @param a the first operand
1047      * @param b the second operand
1048      * @return the smaller of {@code a} and {@code b}.
1049      * @see java.util.function.BinaryOperator
1050      * @since 1.8
1051      */
1052     public static double min(double a, double b) {
1053         return Math.min(a, b);
1054     }
1055 
1056     /** use serialVersionUID from JDK 1.0.2 for interoperability */
1057     private static final long serialVersionUID = -9172774392245257468L;
1058 }