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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 {@code Class} instance representing the primitive type
  127        * {@code double}.
  128        *
  129        * @since JDK1.1
  130        */
  131       public static final Class<Double>   TYPE = (Class<Double>) Class.getPrimitiveClass("double");
  132   
  133       /**
  134        * Returns a string representation of the {@code double}
  135        * argument. All characters mentioned below are ASCII characters.
  136        * <ul>
  137        * <li>If the argument is NaN, the result is the string
  138        *     "{@code NaN}".
  139        * <li>Otherwise, the result is a string that represents the sign and
  140        * magnitude (absolute value) of the argument. If the sign is negative,
  141        * the first character of the result is '{@code -}'
  142        * (<code>'&#92;u002D'</code>); if the sign is positive, no sign character
  143        * appears in the result. As for the magnitude <i>m</i>:
  144        * <ul>
  145        * <li>If <i>m</i> is infinity, it is represented by the characters
  146        * {@code "Infinity"}; thus, positive infinity produces the result
  147        * {@code "Infinity"} and negative infinity produces the result
  148        * {@code "-Infinity"}.
  149        *
  150        * <li>If <i>m</i> is zero, it is represented by the characters
  151        * {@code "0.0"}; thus, negative zero produces the result
  152        * {@code "-0.0"} and positive zero produces the result
  153        * {@code "0.0"}.
  154        *
  155        * <li>If <i>m</i> is greater than or equal to 10<sup>-3</sup> but less
  156        * than 10<sup>7</sup>, then it is represented as the integer part of
  157        * <i>m</i>, in decimal form with no leading zeroes, followed by
  158        * '{@code .}' (<code>'&#92;u002E'</code>), followed by one or
  159        * more decimal digits representing the fractional part of <i>m</i>.
  160        *
  161        * <li>If <i>m</i> is less than 10<sup>-3</sup> or greater than or
  162        * equal to 10<sup>7</sup>, then it is represented in so-called
  163        * "computerized scientific notation." Let <i>n</i> be the unique
  164        * integer such that 10<sup><i>n</i></sup> &le; <i>m</i> {@literal <}
  165        * 10<sup><i>n</i>+1</sup>; then let <i>a</i> be the
  166        * mathematically exact quotient of <i>m</i> and
  167        * 10<sup><i>n</i></sup> so that 1 &le; <i>a</i> {@literal <} 10. The
  168        * magnitude is then represented as the integer part of <i>a</i>,
  169        * as a single decimal digit, followed by '{@code .}'
  170        * (<code>'&#92;u002E'</code>), followed by decimal digits
  171        * representing the fractional part of <i>a</i>, followed by the
  172        * letter '{@code E}' (<code>'&#92;u0045'</code>), followed
  173        * by a representation of <i>n</i> as a decimal integer, as
  174        * produced by the method {@link Integer#toString(int)}.
  175        * </ul>
  176        * </ul>
  177        * How many digits must be printed for the fractional part of
  178        * <i>m</i> or <i>a</i>? There must be at least one digit to represent
  179        * the fractional part, and beyond that as many, but only as many, more
  180        * digits as are needed to uniquely distinguish the argument value from
  181        * adjacent values of type {@code double}. That is, suppose that
  182        * <i>x</i> is the exact mathematical value represented by the decimal
  183        * representation produced by this method for a finite nonzero argument
  184        * <i>d</i>. Then <i>d</i> must be the {@code double} value nearest
  185        * to <i>x</i>; or if two {@code double} values are equally close
  186        * to <i>x</i>, then <i>d</i> must be one of them and the least
  187        * significant bit of the significand of <i>d</i> must be {@code 0}.
  188        *
  189        * <p>To create localized string representations of a floating-point
  190        * value, use subclasses of {@link java.text.NumberFormat}.
  191        *
  192        * @param   d   the {@code double} to be converted.
  193        * @return a string representation of the argument.
  194        */
  195       public static String toString(double d) {
  196           return new FloatingDecimal(d).toJavaFormatString();
  197       }
  198   
  199       /**
  200        * Returns a hexadecimal string representation of the
  201        * {@code double} argument. All characters mentioned below
  202        * are ASCII characters.
  203        *
  204        * <ul>
  205        * <li>If the argument is NaN, the result is the string
  206        *     "{@code NaN}".
  207        * <li>Otherwise, the result is a string that represents the sign
  208        * and magnitude of the argument. If the sign is negative, the
  209        * first character of the result is '{@code -}'
  210        * (<code>'&#92;u002D'</code>); if the sign is positive, no sign
  211        * character appears in the result. As for the magnitude <i>m</i>:
  212        *
  213        * <ul>
  214        * <li>If <i>m</i> is infinity, it is represented by the string
  215        * {@code "Infinity"}; thus, positive infinity produces the
  216        * result {@code "Infinity"} and negative infinity produces
  217        * the result {@code "-Infinity"}.
  218        *
  219        * <li>If <i>m</i> is zero, it is represented by the string
  220        * {@code "0x0.0p0"}; thus, negative zero produces the result
  221        * {@code "-0x0.0p0"} and positive zero produces the result
  222        * {@code "0x0.0p0"}.
  223        *
  224        * <li>If <i>m</i> is a {@code double} value with a
  225        * normalized representation, substrings are used to represent the
  226        * significand and exponent fields.  The significand is
  227        * represented by the characters {@code "0x1."}
  228        * followed by a lowercase hexadecimal representation of the rest
  229        * of the significand as a fraction.  Trailing zeros in the
  230        * hexadecimal representation are removed unless all the digits
  231        * are zero, in which case a single zero is used. Next, the
  232        * exponent is represented by {@code "p"} followed
  233        * by a decimal string of the unbiased exponent as if produced by
  234        * a call to {@link Integer#toString(int) Integer.toString} on the
  235        * exponent value.
  236        *
  237        * <li>If <i>m</i> is a {@code double} value with a subnormal
  238        * representation, the significand is represented by the
  239        * characters {@code "0x0."} followed by a
  240        * hexadecimal representation of the rest of the significand as a
  241        * fraction.  Trailing zeros in the hexadecimal representation are
  242        * removed. Next, the exponent is represented by
  243        * {@code "p-1022"}.  Note that there must be at
  244        * least one nonzero digit in a subnormal significand.
  245        *
  246        * </ul>
  247        *
  248        * </ul>
  249        *
  250        * <table border>
  251        * <caption><h3>Examples</h3></caption>
  252        * <tr><th>Floating-point Value</th><th>Hexadecimal String</th>
  253        * <tr><td>{@code 1.0}</td> <td>{@code 0x1.0p0}</td>
  254        * <tr><td>{@code -1.0}</td>        <td>{@code -0x1.0p0}</td>
  255        * <tr><td>{@code 2.0}</td> <td>{@code 0x1.0p1}</td>
  256        * <tr><td>{@code 3.0}</td> <td>{@code 0x1.8p1}</td>
  257        * <tr><td>{@code 0.5}</td> <td>{@code 0x1.0p-1}</td>
  258        * <tr><td>{@code 0.25}</td>        <td>{@code 0x1.0p-2}</td>
  259        * <tr><td>{@code Double.MAX_VALUE}</td>
  260        *     <td>{@code 0x1.fffffffffffffp1023}</td>
  261        * <tr><td>{@code Minimum Normal Value}</td>
  262        *     <td>{@code 0x1.0p-1022}</td>
  263        * <tr><td>{@code Maximum Subnormal Value}</td>
  264        *     <td>{@code 0x0.fffffffffffffp-1022}</td>
  265        * <tr><td>{@code Double.MIN_VALUE}</td>
  266        *     <td>{@code 0x0.0000000000001p-1022}</td>
  267        * </table>
  268        * @param   d   the {@code double} to be converted.
  269        * @return a hex string representation of the argument.
  270        * @since 1.5
  271        * @author Joseph D. Darcy
  272        */
  273       public static String toHexString(double d) {
  274           /*
  275            * Modeled after the "a" conversion specifier in C99, section
  276            * 7.19.6.1; however, the output of this method is more
  277            * tightly specified.
  278            */
  279           if (!FpUtils.isFinite(d) )
  280               // For infinity and NaN, use the decimal output.
  281               return Double.toString(d);
  282           else {
  283               // Initialized to maximum size of output.
  284               StringBuffer answer = new StringBuffer(24);
  285   
  286               if (FpUtils.rawCopySign(1.0, d) == -1.0) // value is negative,
  287                   answer.append("-");                  // so append sign info
  288   
  289               answer.append("0x");
  290   
  291               d = Math.abs(d);
  292   
  293               if(d == 0.0) {
  294                   answer.append("0.0p0");
  295               }
  296               else {
  297                   boolean subnormal = (d < DoubleConsts.MIN_NORMAL);
  298   
  299                   // Isolate significand bits and OR in a high-order bit
  300                   // so that the string representation has a known
  301                   // length.
  302                   long signifBits = (Double.doubleToLongBits(d)
  303                                      & DoubleConsts.SIGNIF_BIT_MASK) |
  304                       0x1000000000000000L;
  305   
  306                   // Subnormal values have a 0 implicit bit; normal
  307                   // values have a 1 implicit bit.
  308                   answer.append(subnormal ? "0." : "1.");
  309   
  310                   // Isolate the low-order 13 digits of the hex
  311                   // representation.  If all the digits are zero,
  312                   // replace with a single 0; otherwise, remove all
  313                   // trailing zeros.
  314                   String signif = Long.toHexString(signifBits).substring(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" + (subnormal ?
  324                                  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
  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        * <code>
  449        * <pre>
  450        *  final String Digits     = "(\\p{Digit}+)";
  451        *  final String HexDigits  = "(\\p{XDigit}+)";
  452        *  // an exponent is 'e' or 'E' followed by an optionally
  453        *  // signed decimal integer.
  454        *  final String Exp        = "[eE][+-]?"+Digits;
  455        *  final String fpRegex    =
  456        *      ("[\\x00-\\x20]*"+  // Optional leading "whitespace"
  457        *       "[+-]?(" + // Optional sign character
  458        *       "NaN|" +           // "NaN" string
  459        *       "Infinity|" +      // "Infinity" string
  460        *
  461        *       // A decimal floating-point string representing a finite positive
  462        *       // number without a leading sign has at most five basic pieces:
  463        *       // Digits . Digits ExponentPart FloatTypeSuffix
  464        *       //
  465        *       // Since this method allows integer-only strings as input
  466        *       // in addition to strings of floating-point literals, the
  467        *       // two sub-patterns below are simplifications of the grammar
  468        *       // productions from section 3.10.2 of
  469        *       // <cite>The Java&trade; Language Specification</cite>.
  470        *
  471        *       // Digits ._opt Digits_opt ExponentPart_opt FloatTypeSuffix_opt
  472        *       "((("+Digits+"(\\.)?("+Digits+"?)("+Exp+")?)|"+
  473        *
  474        *       // . Digits ExponentPart_opt FloatTypeSuffix_opt
  475        *       "(\\.("+Digits+")("+Exp+")?)|"+
  476        *
  477        *       // Hexadecimal strings
  478        *       "((" +
  479        *        // 0[xX] HexDigits ._opt BinaryExponent FloatTypeSuffix_opt
  480        *        "(0[xX]" + HexDigits + "(\\.)?)|" +
  481        *
  482        *        // 0[xX] HexDigits_opt . HexDigits BinaryExponent FloatTypeSuffix_opt
  483        *        "(0[xX]" + HexDigits + "?(\\.)" + HexDigits + ")" +
  484        *
  485        *        ")[pP][+-]?" + Digits + "))" +
  486        *       "[fFdD]?))" +
  487        *       "[\\x00-\\x20]*");// Optional trailing "whitespace"
  488        *
  489        *  if (Pattern.matches(fpRegex, myString))
  490        *      Double.valueOf(myString); // Will not throw NumberFormatException
  491        *  else {
  492        *      // Perform suitable alternative action
  493        *  }
  494        * </pre>
  495        * </code>
  496        *
  497        * @param      s   the string to be parsed.
  498        * @return     a {@code Double} object holding the value
  499        *             represented by the {@code String} argument.
  500        * @throws     NumberFormatException  if the string does not contain a
  501        *             parsable number.
  502        */
  503       public static Double valueOf(String s) throws NumberFormatException {
  504           return new Double(FloatingDecimal.readJavaFormatString(s).doubleValue());
  505       }
  506   
  507       /**
  508        * Returns a {@code Double} instance representing the specified
  509        * {@code double} value.
  510        * If a new {@code Double} instance is not required, this method
  511        * should generally be used in preference to the constructor
  512        * {@link #Double(double)}, as this method is likely to yield
  513        * significantly better space and time performance by caching
  514        * frequently requested values.
  515        *
  516        * @param  d a double value.
  517        * @return a {@code Double} instance representing {@code d}.
  518        * @since  1.5
  519        */
  520       public static Double valueOf(double d) {
  521           return new Double(d);
  522       }
  523   
  524       /**
  525        * Returns a new {@code double} initialized to the value
  526        * represented by the specified {@code String}, as performed
  527        * by the {@code valueOf} method of class
  528        * {@code Double}.
  529        *
  530        * @param  s   the string to be parsed.
  531        * @return the {@code double} value represented by the string
  532        *         argument.
  533        * @throws NullPointerException  if the string is null
  534        * @throws NumberFormatException if the string does not contain
  535        *         a parsable {@code double}.
  536        * @see    java.lang.Double#valueOf(String)
  537        * @since 1.2
  538        */
  539       public static double parseDouble(String s) throws NumberFormatException {
  540           return FloatingDecimal.readJavaFormatString(s).doubleValue();
  541       }
  542   
  543       /**
  544        * Returns {@code true} if the specified number is a
  545        * Not-a-Number (NaN) value, {@code false} otherwise.
  546        *
  547        * @param   v   the value to be tested.
  548        * @return  {@code true} if the value of the argument is NaN;
  549        *          {@code false} otherwise.
  550        */
  551       static public boolean isNaN(double v) {
  552           return (v != v);
  553       }
  554   
  555       /**
  556        * Returns {@code true} if the specified number is infinitely
  557        * large in magnitude, {@code false} otherwise.
  558        *
  559        * @param   v   the value to be tested.
  560        * @return  {@code true} if the value of the argument is positive
  561        *          infinity or negative infinity; {@code false} otherwise.
  562        */
  563       static public boolean isInfinite(double v) {
  564           return (v == POSITIVE_INFINITY) || (v == NEGATIVE_INFINITY);
  565       }
  566   
  567       /**
  568        * The value of the Double.
  569        *
  570        * @serial
  571        */
  572       private final double value;
  573   
  574       /**
  575        * Constructs a newly allocated {@code Double} object that
  576        * represents the primitive {@code double} argument.
  577        *
  578        * @param   value   the value to be represented by the {@code Double}.
  579        */
  580       public Double(double value) {
  581           this.value = value;
  582       }
  583   
  584       /**
  585        * Constructs a newly allocated {@code Double} object that
  586        * represents the floating-point value of type {@code double}
  587        * represented by the string. The string is converted to a
  588        * {@code double} value as if by the {@code valueOf} method.
  589        *
  590        * @param  s  a string to be converted to a {@code Double}.
  591        * @throws    NumberFormatException  if the string does not contain a
  592        *            parsable number.
  593        * @see       java.lang.Double#valueOf(java.lang.String)
  594        */
  595       public Double(String s) throws NumberFormatException {
  596           // REMIND: this is inefficient
  597           this(valueOf(s).doubleValue());
  598       }
  599   
  600       /**
  601        * Returns {@code true} if this {@code Double} value is
  602        * a Not-a-Number (NaN), {@code false} otherwise.
  603        *
  604        * @return  {@code true} if the value represented by this object is
  605        *          NaN; {@code false} otherwise.
  606        */
  607       public boolean isNaN() {
  608           return isNaN(value);
  609       }
  610   
  611       /**
  612        * Returns {@code true} if this {@code Double} value is
  613        * infinitely large in magnitude, {@code false} otherwise.
  614        *
  615        * @return  {@code true} if the value represented by this object is
  616        *          positive infinity or negative infinity;
  617        *          {@code false} otherwise.
  618        */
  619       public boolean isInfinite() {
  620           return isInfinite(value);
  621       }
  622   
  623       /**
  624        * Returns a string representation of this {@code Double} object.
  625        * The primitive {@code double} value represented by this
  626        * object is converted to a string exactly as if by the method
  627        * {@code toString} of one argument.
  628        *
  629        * @return  a {@code String} representation of this object.
  630        * @see java.lang.Double#toString(double)
  631        */
  632       public String toString() {
  633           return toString(value);
  634       }
  635   
  636       /**
  637        * Returns the value of this {@code Double} as a {@code byte} (by
  638        * casting to a {@code byte}).
  639        *
  640        * @return  the {@code double} value represented by this object
  641        *          converted to type {@code byte}
  642        * @since JDK1.1
  643        */
  644       public byte byteValue() {
  645           return (byte)value;
  646       }
  647   
  648       /**
  649        * Returns the value of this {@code Double} as a
  650        * {@code short} (by casting to a {@code short}).
  651        *
  652        * @return  the {@code double} value represented by this object
  653        *          converted to type {@code short}
  654        * @since JDK1.1
  655        */
  656       public short shortValue() {
  657           return (short)value;
  658       }
  659   
  660       /**
  661        * Returns the value of this {@code Double} as an
  662        * {@code int} (by casting to type {@code int}).
  663        *
  664        * @return  the {@code double} value represented by this object
  665        *          converted to type {@code int}
  666        */
  667       public int intValue() {
  668           return (int)value;
  669       }
  670   
  671       /**
  672        * Returns the value of this {@code Double} as a
  673        * {@code long} (by casting to type {@code long}).
  674        *
  675        * @return  the {@code double} value represented by this object
  676        *          converted to type {@code long}
  677        */
  678       public long longValue() {
  679           return (long)value;
  680       }
  681   
  682       /**
  683        * Returns the {@code float} value of this
  684        * {@code Double} object.
  685        *
  686        * @return  the {@code double} value represented by this object
  687        *          converted to type {@code float}
  688        * @since JDK1.0
  689        */
  690       public float floatValue() {
  691           return (float)value;
  692       }
  693   
  694       /**
  695        * Returns the {@code double} value of this
  696        * {@code Double} object.
  697        *
  698        * @return the {@code double} value represented by this object
  699        */
  700       public double doubleValue() {
  701           return (double)value;
  702       }
  703   
  704       /**
  705        * Returns a hash code for this {@code Double} object. The
  706        * result is the exclusive OR of the two halves of the
  707        * {@code long} integer bit representation, exactly as
  708        * produced by the method {@link #doubleToLongBits(double)}, of
  709        * the primitive {@code double} value represented by this
  710        * {@code Double} object. That is, the hash code is the value
  711        * of the expression:
  712        *
  713        * <blockquote>
  714        *  {@code (int)(v^(v>>>32))}
  715        * </blockquote>
  716        *
  717        * where {@code v} is defined by:
  718        *
  719        * <blockquote>
  720        *  {@code long v = Double.doubleToLongBits(this.doubleValue());}
  721        * </blockquote>
  722        *
  723        * @return  a {@code hash code} value for this object.
  724        */
  725       public int hashCode() {
  726           long bits = doubleToLongBits(value);
  727           return (int)(bits ^ (bits >>> 32));
  728       }
  729   
  730       /**
  731        * Compares this object against the specified object.  The result
  732        * is {@code true} if and only if the argument is not
  733        * {@code null} and is a {@code Double} object that
  734        * represents a {@code double} that has the same value as the
  735        * {@code double} represented by this object. For this
  736        * purpose, two {@code double} values are considered to be
  737        * the same if and only if the method {@link
  738        * #doubleToLongBits(double)} returns the identical
  739        * {@code long} value when applied to each.
  740        *
  741        * <p>Note that in most cases, for two instances of class
  742        * {@code Double}, {@code d1} and {@code d2}, the
  743        * value of {@code d1.equals(d2)} is {@code true} if and
  744        * only if
  745        *
  746        * <blockquote>
  747        *  {@code d1.doubleValue() == d2.doubleValue()}
  748        * </blockquote>
  749        *
  750        * <p>also has the value {@code true}. However, there are two
  751        * exceptions:
  752        * <ul>
  753        * <li>If {@code d1} and {@code d2} both represent
  754        *     {@code Double.NaN}, then the {@code equals} method
  755        *     returns {@code true}, even though
  756        *     {@code Double.NaN==Double.NaN} has the value
  757        *     {@code false}.
  758        * <li>If {@code d1} represents {@code +0.0} while
  759        *     {@code d2} represents {@code -0.0}, or vice versa,
  760        *     the {@code equal} test has the value {@code false},
  761        *     even though {@code +0.0==-0.0} has the value {@code true}.
  762        * </ul>
  763        * This definition allows hash tables to operate properly.
  764        * @param   obj   the object to compare with.
  765        * @return  {@code true} if the objects are the same;
  766        *          {@code false} otherwise.
  767        * @see java.lang.Double#doubleToLongBits(double)
  768        */
  769       public boolean equals(Object obj) {
  770           return (obj instanceof Double)
  771                  && (doubleToLongBits(((Double)obj).value) ==
  772                         doubleToLongBits(value));
  773       }
  774   
  775       /**
  776        * Returns a representation of the specified floating-point value
  777        * according to the IEEE 754 floating-point "double
  778        * format" bit layout.
  779        *
  780        * <p>Bit 63 (the bit that is selected by the mask
  781        * {@code 0x8000000000000000L}) represents the sign of the
  782        * floating-point number. Bits
  783        * 62-52 (the bits that are selected by the mask
  784        * {@code 0x7ff0000000000000L}) represent the exponent. Bits 51-0
  785        * (the bits that are selected by the mask
  786        * {@code 0x000fffffffffffffL}) represent the significand
  787        * (sometimes called the mantissa) of the floating-point number.
  788        *
  789        * <p>If the argument is positive infinity, the result is
  790        * {@code 0x7ff0000000000000L}.
  791        *
  792        * <p>If the argument is negative infinity, the result is
  793        * {@code 0xfff0000000000000L}.
  794        *
  795        * <p>If the argument is NaN, the result is
  796        * {@code 0x7ff8000000000000L}.
  797        *
  798        * <p>In all cases, the result is a {@code long} integer that, when
  799        * given to the {@link #longBitsToDouble(long)} method, will produce a
  800        * floating-point value the same as the argument to
  801        * {@code doubleToLongBits} (except all NaN values are
  802        * collapsed to a single "canonical" NaN value).
  803        *
  804        * @param   value   a {@code double} precision floating-point number.
  805        * @return the bits that represent the floating-point number.
  806        */
  807       public static long doubleToLongBits(double value) {
  808           long result = doubleToRawLongBits(value);
  809           // Check for NaN based on values of bit fields, maximum
  810           // exponent and nonzero significand.
  811           if ( ((result & DoubleConsts.EXP_BIT_MASK) ==
  812                 DoubleConsts.EXP_BIT_MASK) &&
  813                (result & DoubleConsts.SIGNIF_BIT_MASK) != 0L)
  814               result = 0x7ff8000000000000L;
  815           return result;
  816       }
  817   
  818       /**
  819        * Returns a representation of the specified floating-point value
  820        * according to the IEEE 754 floating-point "double
  821        * format" bit layout, preserving Not-a-Number (NaN) values.
  822        *
  823        * <p>Bit 63 (the bit that is selected by the mask
  824        * {@code 0x8000000000000000L}) represents the sign of the
  825        * floating-point number. Bits
  826        * 62-52 (the bits that are selected by the mask
  827        * {@code 0x7ff0000000000000L}) represent the exponent. Bits 51-0
  828        * (the bits that are selected by the mask
  829        * {@code 0x000fffffffffffffL}) represent the significand
  830        * (sometimes called the mantissa) of the floating-point number.
  831        *
  832        * <p>If the argument is positive infinity, the result is
  833        * {@code 0x7ff0000000000000L}.
  834        *
  835        * <p>If the argument is negative infinity, the result is
  836        * {@code 0xfff0000000000000L}.
  837        *
  838        * <p>If the argument is NaN, the result is the {@code long}
  839        * integer representing the actual NaN value.  Unlike the
  840        * {@code doubleToLongBits} method,
  841        * {@code doubleToRawLongBits} does not collapse all the bit
  842        * patterns encoding a NaN to a single "canonical" NaN
  843        * value.
  844        *
  845        * <p>In all cases, the result is a {@code long} integer that,
  846        * when given to the {@link #longBitsToDouble(long)} method, will
  847        * produce a floating-point value the same as the argument to
  848        * {@code doubleToRawLongBits}.
  849        *
  850        * @param   value   a {@code double} precision floating-point number.
  851        * @return the bits that represent the floating-point number.
  852        * @since 1.3
  853        */
  854       public static native long doubleToRawLongBits(double value);
  855   
  856       /**
  857        * Returns the {@code double} value corresponding to a given
  858        * bit representation.
  859        * The argument is considered to be a representation of a
  860        * floating-point value according to the IEEE 754 floating-point
  861        * "double format" bit layout.
  862        *
  863        * <p>If the argument is {@code 0x7ff0000000000000L}, the result
  864        * is positive infinity.
  865        *
  866        * <p>If the argument is {@code 0xfff0000000000000L}, the result
  867        * is negative infinity.
  868        *
  869        * <p>If the argument is any value in the range
  870        * {@code 0x7ff0000000000001L} through
  871        * {@code 0x7fffffffffffffffL} or in the range
  872        * {@code 0xfff0000000000001L} through
  873        * {@code 0xffffffffffffffffL}, the result is a NaN.  No IEEE
  874        * 754 floating-point operation provided by Java can distinguish
  875        * between two NaN values of the same type with different bit
  876        * patterns.  Distinct values of NaN are only distinguishable by
  877        * use of the {@code Double.doubleToRawLongBits} method.
  878        *
  879        * <p>In all other cases, let <i>s</i>, <i>e</i>, and <i>m</i> be three
  880        * values that can be computed from the argument:
  881        *
  882        * <blockquote><pre>
  883        * int s = ((bits &gt;&gt; 63) == 0) ? 1 : -1;
  884        * int e = (int)((bits &gt;&gt; 52) & 0x7ffL);
  885        * long m = (e == 0) ?
  886        *                 (bits & 0xfffffffffffffL) &lt;&lt; 1 :
  887        *                 (bits & 0xfffffffffffffL) | 0x10000000000000L;
  888        * </pre></blockquote>
  889        *
  890        * Then the floating-point result equals the value of the mathematical
  891        * expression <i>s</i>&middot;<i>m</i>&middot;2<sup><i>e</i>-1075</sup>.
  892        *
  893        * <p>Note that this method may not be able to return a
  894        * {@code double} NaN with exactly same bit pattern as the
  895        * {@code long} argument.  IEEE 754 distinguishes between two
  896        * kinds of NaNs, quiet NaNs and <i>signaling NaNs</i>.  The
  897        * differences between the two kinds of NaN are generally not
  898        * visible in Java.  Arithmetic operations on signaling NaNs turn
  899        * them into quiet NaNs with a different, but often similar, bit
  900        * pattern.  However, on some processors merely copying a
  901        * signaling NaN also performs that conversion.  In particular,
  902        * copying a signaling NaN to return it to the calling method
  903        * may perform this conversion.  So {@code longBitsToDouble}
  904        * may not be able to return a {@code double} with a
  905        * signaling NaN bit pattern.  Consequently, for some
  906        * {@code long} values,
  907        * {@code doubleToRawLongBits(longBitsToDouble(start))} may
  908        * <i>not</i> equal {@code start}.  Moreover, which
  909        * particular bit patterns represent signaling NaNs is platform
  910        * dependent; although all NaN bit patterns, quiet or signaling,
  911        * must be in the NaN range identified above.
  912        *
  913        * @param   bits   any {@code long} integer.
  914        * @return  the {@code double} floating-point value with the same
  915        *          bit pattern.
  916        */
  917       public static native double longBitsToDouble(long bits);
  918   
  919       /**
  920        * Compares two {@code Double} objects numerically.  There
  921        * are two ways in which comparisons performed by this method
  922        * differ from those performed by the Java language numerical
  923        * comparison operators ({@code <, <=, ==, >=, >})
  924        * when applied to primitive {@code double} values:
  925        * <ul><li>
  926        *          {@code Double.NaN} is considered by this method
  927        *          to be equal to itself and greater than all other
  928        *          {@code double} values (including
  929        *          {@code Double.POSITIVE_INFINITY}).
  930        * <li>
  931        *          {@code 0.0d} is considered by this method to be greater
  932        *          than {@code -0.0d}.
  933        * </ul>
  934        * This ensures that the <i>natural ordering</i> of
  935        * {@code Double} objects imposed by this method is <i>consistent
  936        * with equals</i>.
  937        *
  938        * @param   anotherDouble   the {@code Double} to be compared.
  939        * @return  the value {@code 0} if {@code anotherDouble} is
  940        *          numerically equal to this {@code Double}; a value
  941        *          less than {@code 0} if this {@code Double}
  942        *          is numerically less than {@code anotherDouble};
  943        *          and a value greater than {@code 0} if this
  944        *          {@code Double} is numerically greater than
  945        *          {@code anotherDouble}.
  946        *
  947        * @since   1.2
  948        */
  949       public int compareTo(Double anotherDouble) {
  950           return Double.compare(value, anotherDouble.value);
  951       }
  952   
  953       /**
  954        * Compares the two specified {@code double} values. The sign
  955        * of the integer value returned is the same as that of the
  956        * integer that would be returned by the call:
  957        * <pre>
  958        *    new Double(d1).compareTo(new Double(d2))
  959        * </pre>
  960        *
  961        * @param   d1        the first {@code double} to compare
  962        * @param   d2        the second {@code double} to compare
  963        * @return  the value {@code 0} if {@code d1} is
  964        *          numerically equal to {@code d2}; a value less than
  965        *          {@code 0} if {@code d1} is numerically less than
  966        *          {@code d2}; and a value greater than {@code 0}
  967        *          if {@code d1} is numerically greater than
  968        *          {@code d2}.
  969        * @since 1.4
  970        */
  971       public static int compare(double d1, double d2) {
  972           if (d1 < d2)
  973               return -1;           // Neither val is NaN, thisVal is smaller
  974           if (d1 > d2)
  975               return 1;            // Neither val is NaN, thisVal is larger
  976   
  977           // Cannot use doubleToRawLongBits because of possibility of NaNs.
  978           long thisBits    = Double.doubleToLongBits(d1);
  979           long anotherBits = Double.doubleToLongBits(d2);
  980   
  981           return (thisBits == anotherBits ?  0 : // Values are equal
  982                   (thisBits < anotherBits ? -1 : // (-0.0, 0.0) or (!NaN, NaN)
  983                    1));                          // (0.0, -0.0) or (NaN, !NaN)
  984       }
  985   
  986       /** use serialVersionUID from JDK 1.0.2 for interoperability */
  987       private static final long serialVersionUID = -9172774392245257468L;
  988   }

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