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   * Copyright (c) 1994, 2013, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.  Oracle designates this
   * particular file as subject to the "Classpath" exception as provided
   * by Oracle in the LICENSE file that accompanied this code.
   *
   * This code is distributed in the hope that it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   * version 2 for more details (a copy is included in the LICENSE file that
   * accompanied this code).
   *
   * You should have received a copy of the GNU General Public License version
   * 2 along with this work; if not, write to the Free Software Foundation,
   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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   * questions.
   */
  
  package java.lang;
  
  import sun.misc.FloatingDecimal;
  import sun.misc.FpUtils;
  import sun.misc.DoubleConsts;
  
  /**
   * The {@code Double} class wraps a value of the primitive type
   * {@code double} in an object. An object of type
   * {@code Double} contains a single field whose type is
   * {@code double}.
   *
   * <p>In addition, this class provides several methods for converting a
   * {@code double} to a {@code String} and a
   * {@code String} to a {@code double}, as well as other
   * constants and methods useful when dealing with a
   * {@code double}.
   *
   * @author  Lee Boynton
   * @author  Arthur van Hoff
   * @author  Joseph D. Darcy
   * @since JDK1.0
   */
  public final class Double extends Number implements Comparable<Double> {
      /**
       * A constant holding the positive infinity of type
       * {@code double}. It is equal to the value returned by
       * {@code Double.longBitsToDouble(0x7ff0000000000000L)}.
       */
      public static final double POSITIVE_INFINITY = 1.0 / 0.0;
  
      /**
       * A constant holding the negative infinity of type
       * {@code double}. It is equal to the value returned by
       * {@code Double.longBitsToDouble(0xfff0000000000000L)}.
       */
      public static final double NEGATIVE_INFINITY = -1.0 / 0.0;
  
      /**
       * A constant holding a Not-a-Number (NaN) value of type
       * {@code double}. It is equivalent to the value returned by
       * {@code Double.longBitsToDouble(0x7ff8000000000000L)}.
       */
      public static final double NaN = 0.0d / 0.0;
  
      /**
       * A constant holding the largest positive finite value of type
       * {@code double},
       * (2-2<sup>-52</sup>)&middot;2<sup>1023</sup>.  It is equal to
       * the hexadecimal floating-point literal
       * {@code 0x1.fffffffffffffP+1023} and also equal to
       * {@code Double.longBitsToDouble(0x7fefffffffffffffL)}.
       */
      public static final double MAX_VALUE = 0x1.fffffffffffffP+1023; // 1.7976931348623157e+308
  
      /**
       * A constant holding the smallest positive normal value of type
       * {@code double}, 2<sup>-1022</sup>.  It is equal to the
       * hexadecimal floating-point literal {@code 0x1.0p-1022} and also
       * equal to {@code Double.longBitsToDouble(0x0010000000000000L)}.
       *
       * @since 1.6
       */
      public static final double MIN_NORMAL = 0x1.0p-1022; // 2.2250738585072014E-308
  
      /**
       * A constant holding the smallest positive nonzero value of type
       * {@code double}, 2<sup>-1074</sup>. It is equal to the
       * hexadecimal floating-point literal
       * {@code 0x0.0000000000001P-1022} and also equal to
       * {@code Double.longBitsToDouble(0x1L)}.
       */
      public static final double MIN_VALUE = 0x0.0000000000001P-1022; // 4.9e-324
  
      /**
       * Maximum exponent a finite {@code double} variable may have.
       * It is equal to the value returned by
       * {@code Math.getExponent(Double.MAX_VALUE)}.
       *
       * @since 1.6
       */
      public static final int MAX_EXPONENT = 1023;
  
      /**
       * Minimum exponent a normalized {@code double} variable may
       * have.  It is equal to the value returned by
       * {@code Math.getExponent(Double.MIN_NORMAL)}.
       *
       * @since 1.6
       */
      public static final int MIN_EXPONENT = -1022;
  
      /**
       * The number of bits used to represent a {@code double} value.
       *
       * @since 1.5
       */
      public static final int SIZE = 64;
  
      /**
       * The number of bytes used to represent a {@code double} value.
       *
       * @since 1.8
       */
      public static final int BYTES = SIZE / Byte.SIZE;
  
      /**
       * The {@code Class} instance representing the primitive type
       * {@code double}.
       *
       * @since JDK1.1
       */
      @SuppressWarnings("unchecked")
      public static final Class<Double>   TYPE = (Class<Double>) Class.getPrimitiveClass("double");
  
      /**
       * Returns a string representation of the {@code double}
       * argument. All characters mentioned below are ASCII characters.
       * <ul>
       * <li>If the argument is NaN, the result is the string
       *     "{@code NaN}".
       * <li>Otherwise, the result is a string that represents the sign and
       * magnitude (absolute value) of the argument. If the sign is negative,
       * the first character of the result is '{@code -}'
       * ({@code '\u005Cu002D'}); if the sign is positive, no sign character
       * appears in the result. As for the magnitude <i>m</i>:
       * <ul>
       * <li>If <i>m</i> is infinity, it is represented by the characters
       * {@code "Infinity"}; thus, positive infinity produces the result
       * {@code "Infinity"} and negative infinity produces the result
       * {@code "-Infinity"}.
       *
       * <li>If <i>m</i> is zero, it is represented by the characters
       * {@code "0.0"}; thus, negative zero produces the result
       * {@code "-0.0"} and positive zero produces the result
       * {@code "0.0"}.
       *
       * <li>If <i>m</i> is greater than or equal to 10<sup>-3</sup> but less
       * than 10<sup>7</sup>, then it is represented as the integer part of
       * <i>m</i>, in decimal form with no leading zeroes, followed by
       * '{@code .}' ({@code '\u005Cu002E'}), followed by one or
       * more decimal digits representing the fractional part of <i>m</i>.
       *
       * <li>If <i>m</i> is less than 10<sup>-3</sup> or greater than or
       * equal to 10<sup>7</sup>, then it is represented in so-called
       * "computerized scientific notation." Let <i>n</i> be the unique
       * integer such that 10<sup><i>n</i></sup> &le; <i>m</i> {@literal <}
       * 10<sup><i>n</i>+1</sup>; then let <i>a</i> be the
       * mathematically exact quotient of <i>m</i> and
       * 10<sup><i>n</i></sup> so that 1 &le; <i>a</i> {@literal <} 10. The
       * magnitude is then represented as the integer part of <i>a</i>,
       * as a single decimal digit, followed by '{@code .}'
       * ({@code '\u005Cu002E'}), followed by decimal digits
       * representing the fractional part of <i>a</i>, followed by the
       * letter '{@code E}' ({@code '\u005Cu0045'}), followed
       * by a representation of <i>n</i> as a decimal integer, as
       * produced by the method {@link Integer#toString(int)}.
       * </ul>
       * </ul>
       * How many digits must be printed for the fractional part of
       * <i>m</i> or <i>a</i>? There must be at least one digit to represent
       * the fractional part, and beyond that as many, but only as many, more
       * digits as are needed to uniquely distinguish the argument value from
       * adjacent values of type {@code double}. That is, suppose that
       * <i>x</i> is the exact mathematical value represented by the decimal
       * representation produced by this method for a finite nonzero argument
       * <i>d</i>. Then <i>d</i> must be the {@code double} value nearest
       * to <i>x</i>; or if two {@code double} values are equally close
       * to <i>x</i>, then <i>d</i> must be one of them and the least
       * significant bit of the significand of <i>d</i> must be {@code 0}.
       *
       * <p>To create localized string representations of a floating-point
       * value, use subclasses of {@link java.text.NumberFormat}.
       *
       * @param   d   the {@code double} to be converted.
       * @return a string representation of the argument.
       */
      public static String toString(double d) {
          return FloatingDecimal.toJavaFormatString(d);
      }
  
      /**
       * Returns a hexadecimal string representation of the
       * {@code double} argument. All characters mentioned below
       * are ASCII characters.
       *
       * <ul>
       * <li>If the argument is NaN, the result is the string
       *     "{@code NaN}".
       * <li>Otherwise, the result is a string that represents the sign
       * and magnitude of the argument. If the sign is negative, the
       * first character of the result is '{@code -}'
       * ({@code '\u005Cu002D'}); if the sign is positive, no sign
       * character appears in the result. As for the magnitude <i>m</i>:
       *
       * <ul>
       * <li>If <i>m</i> is infinity, it is represented by the string
       * {@code "Infinity"}; thus, positive infinity produces the
       * result {@code "Infinity"} and negative infinity produces
       * the result {@code "-Infinity"}.
       *
       * <li>If <i>m</i> is zero, it is represented by the string
       * {@code "0x0.0p0"}; thus, negative zero produces the result
       * {@code "-0x0.0p0"} and positive zero produces the result
       * {@code "0x0.0p0"}.
       *
       * <li>If <i>m</i> is a {@code double} value with a
       * normalized representation, substrings are used to represent the
       * significand and exponent fields.  The significand is
       * represented by the characters {@code "0x1."}
       * followed by a lowercase hexadecimal representation of the rest
       * of the significand as a fraction.  Trailing zeros in the
       * hexadecimal representation are removed unless all the digits
       * are zero, in which case a single zero is used. Next, the
       * exponent is represented by {@code "p"} followed
       * by a decimal string of the unbiased exponent as if produced by
       * a call to {@link Integer#toString(int) Integer.toString} on the
       * exponent value.
       *
       * <li>If <i>m</i> is a {@code double} value with a subnormal
       * representation, the significand is represented by the
       * characters {@code "0x0."} followed by a
       * hexadecimal representation of the rest of the significand as a
       * fraction.  Trailing zeros in the hexadecimal representation are
       * removed. Next, the exponent is represented by
       * {@code "p-1022"}.  Note that there must be at
       * least one nonzero digit in a subnormal significand.
       *
       * </ul>
       *
       * </ul>
       *
       * <table border>
       * <caption>Examples</caption>
       * <tr><th>Floating-point Value</th><th>Hexadecimal String</th>
       * <tr><td>{@code 1.0}</td> <td>{@code 0x1.0p0}</td>
       * <tr><td>{@code -1.0}</td>        <td>{@code -0x1.0p0}</td>
       * <tr><td>{@code 2.0}</td> <td>{@code 0x1.0p1}</td>
       * <tr><td>{@code 3.0}</td> <td>{@code 0x1.8p1}</td>
       * <tr><td>{@code 0.5}</td> <td>{@code 0x1.0p-1}</td>
       * <tr><td>{@code 0.25}</td>        <td>{@code 0x1.0p-2}</td>
       * <tr><td>{@code Double.MAX_VALUE}</td>
       *     <td>{@code 0x1.fffffffffffffp1023}</td>
       * <tr><td>{@code Minimum Normal Value}</td>
       *     <td>{@code 0x1.0p-1022}</td>
       * <tr><td>{@code Maximum Subnormal Value}</td>
       *     <td>{@code 0x0.fffffffffffffp-1022}</td>
       * <tr><td>{@code Double.MIN_VALUE}</td>
       *     <td>{@code 0x0.0000000000001p-1022}</td>
       * </table>
       * @param   d   the {@code double} to be converted.
       * @return a hex string representation of the argument.
       * @since 1.5
       * @author Joseph D. Darcy
       */
      public static String toHexString(double d) {
          /*
           * Modeled after the "a" conversion specifier in C99, section
           * 7.19.6.1; however, the output of this method is more
           * tightly specified.
           */
          if (!isFinite(d) )
              // For infinity and NaN, use the decimal output.
              return Double.toString(d);
          else {
              // Initialized to maximum size of output.
              StringBuilder answer = new StringBuilder(24);
  
              if (Math.copySign(1.0, d) == -1.0)    // value is negative,
                  answer.append("-");                  // so append sign info
  
              answer.append("0x");
  
              d = Math.abs(d);
  
              if(d == 0.0) {
                  answer.append("0.0p0");
              } else {
                  boolean subnormal = (d < DoubleConsts.MIN_NORMAL);
  
                  // Isolate significand bits and OR in a high-order bit
                  // so that the string representation has a known
                  // length.
                  long signifBits = (Double.doubleToLongBits(d)
                                     & DoubleConsts.SIGNIF_BIT_MASK) |
                      0x1000000000000000L;
  
                  // Subnormal values have a 0 implicit bit; normal
                  // values have a 1 implicit bit.
                  answer.append(subnormal ? "0." : "1.");
  
                  // Isolate the low-order 13 digits of the hex
                  // representation.  If all the digits are zero,
                  // replace with a single 0; otherwise, remove all
                  // trailing zeros.
                  String signif = Long.toHexString(signifBits).substring(3,16);
                  answer.append(signif.equals("0000000000000") ? // 13 zeros
                                "0":
                                signif.replaceFirst("0{1,12}$", ""));
  
                  answer.append('p');
                  // If the value is subnormal, use the E_min exponent
                  // value for double; otherwise, extract and report d's
                  // exponent (the representation of a subnormal uses
                  // E_min -1).
                  answer.append(subnormal ?
                                DoubleConsts.MIN_EXPONENT:
                                Math.getExponent(d));
              }
              return answer.toString();
          }
      }
  
      /**
       * Returns a {@code Double} object holding the
       * {@code double} value represented by the argument string
       * {@code s}.
       *
       * <p>If {@code s} is {@code null}, then a
       * {@code NullPointerException} is thrown.
       *
       * <p>Leading and trailing whitespace characters in {@code s}
       * are ignored.  Whitespace is removed as if by the {@link
       * String#trim} method; that is, both ASCII space and control
       * characters are removed. The rest of {@code s} should
       * constitute a <i>FloatValue</i> as described by the lexical
       * syntax rules:
       *
       * <blockquote>
       * <dl>
       * <dt><i>FloatValue:</i>
       * <dd><i>Sign<sub>opt</sub></i> {@code NaN}
       * <dd><i>Sign<sub>opt</sub></i> {@code Infinity}
       * <dd><i>Sign<sub>opt</sub> FloatingPointLiteral</i>
       * <dd><i>Sign<sub>opt</sub> HexFloatingPointLiteral</i>
       * <dd><i>SignedInteger</i>
       * </dl>
       *
       * <dl>
       * <dt><i>HexFloatingPointLiteral</i>:
       * <dd> <i>HexSignificand BinaryExponent FloatTypeSuffix<sub>opt</sub></i>
       * </dl>
       *
       * <dl>
       * <dt><i>HexSignificand:</i>
       * <dd><i>HexNumeral</i>
       * <dd><i>HexNumeral</i> {@code .}
       * <dd>{@code 0x} <i>HexDigits<sub>opt</sub>
       *     </i>{@code .}<i> HexDigits</i>
       * <dd>{@code 0X}<i> HexDigits<sub>opt</sub>
       *     </i>{@code .} <i>HexDigits</i>
       * </dl>
       *
       * <dl>
       * <dt><i>BinaryExponent:</i>
       * <dd><i>BinaryExponentIndicator SignedInteger</i>
       * </dl>
       *
       * <dl>
       * <dt><i>BinaryExponentIndicator:</i>
       * <dd>{@code p}
       * <dd>{@code P}
       * </dl>
       *
       * </blockquote>
       *
       * where <i>Sign</i>, <i>FloatingPointLiteral</i>,
       * <i>HexNumeral</i>, <i>HexDigits</i>, <i>SignedInteger</i> and
       * <i>FloatTypeSuffix</i> are as defined in the lexical structure
       * sections of
       * <cite>The Java&trade; Language Specification</cite>,
       * except that underscores are not accepted between digits.
       * If {@code s} does not have the form of
       * a <i>FloatValue</i>, then a {@code NumberFormatException}
       * is thrown. Otherwise, {@code s} is regarded as
       * representing an exact decimal value in the usual
       * "computerized scientific notation" or as an exact
       * hexadecimal value; this exact numerical value is then
       * conceptually converted to an "infinitely precise"
       * binary value that is then rounded to type {@code double}
       * by the usual round-to-nearest rule of IEEE 754 floating-point
       * arithmetic, which includes preserving the sign of a zero
       * value.
       *
       * Note that the round-to-nearest rule also implies overflow and
       * underflow behaviour; if the exact value of {@code s} is large
       * enough in magnitude (greater than or equal to ({@link
       * #MAX_VALUE} + {@link Math#ulp(double) ulp(MAX_VALUE)}/2),
       * rounding to {@code double} will result in an infinity and if the
       * exact value of {@code s} is small enough in magnitude (less
       * than or equal to {@link #MIN_VALUE}/2), rounding to float will
       * result in a zero.
       *
       * Finally, after rounding a {@code Double} object representing
       * this {@code double} value is returned.
       *
       * <p> To interpret localized string representations of a
       * floating-point value, use subclasses of {@link
       * java.text.NumberFormat}.
       *
       * <p>Note that trailing format specifiers, specifiers that
       * determine the type of a floating-point literal
       * ({@code 1.0f} is a {@code float} value;
       * {@code 1.0d} is a {@code double} value), do
       * <em>not</em> influence the results of this method.  In other
       * words, the numerical value of the input string is converted
       * directly to the target floating-point type.  The two-step
       * sequence of conversions, string to {@code float} followed
       * by {@code float} to {@code double}, is <em>not</em>
       * equivalent to converting a string directly to
       * {@code double}. For example, the {@code float}
       * literal {@code 0.1f} is equal to the {@code double}
       * value {@code 0.10000000149011612}; the {@code float}
       * literal {@code 0.1f} represents a different numerical
       * value than the {@code double} literal
       * {@code 0.1}. (The numerical value 0.1 cannot be exactly
       * represented in a binary floating-point number.)
       *
       * <p>To avoid calling this method on an invalid string and having
       * a {@code NumberFormatException} be thrown, the regular
       * expression below can be used to screen the input string:
       *
       * <pre>{@code
       *  final String Digits     = "(\\p{Digit}+)";
       *  final String HexDigits  = "(\\p{XDigit}+)";
       *  // an exponent is 'e' or 'E' followed by an optionally
       *  // signed decimal integer.
       *  final String Exp        = "[eE][+-]?"+Digits;
       *  final String fpRegex    =
       *      ("[\\x00-\\x20]*"+  // Optional leading "whitespace"
       *       "[+-]?(" + // Optional sign character
       *       "NaN|" +           // "NaN" string
       *       "Infinity|" +      // "Infinity" string
       *
       *       // A decimal floating-point string representing a finite positive
       *       // number without a leading sign has at most five basic pieces:
       *       // Digits . Digits ExponentPart FloatTypeSuffix
       *       //
       *       // Since this method allows integer-only strings as input
       *       // in addition to strings of floating-point literals, the
       *       // two sub-patterns below are simplifications of the grammar
       *       // productions from section 3.10.2 of
       *       // The Java Language Specification.
       *
       *       // Digits ._opt Digits_opt ExponentPart_opt FloatTypeSuffix_opt
       *       "((("+Digits+"(\\.)?("+Digits+"?)("+Exp+")?)|"+
       *
       *       // . Digits ExponentPart_opt FloatTypeSuffix_opt
       *       "(\\.("+Digits+")("+Exp+")?)|"+
       *
       *       // Hexadecimal strings
       *       "((" +
       *        // 0[xX] HexDigits ._opt BinaryExponent FloatTypeSuffix_opt
       *        "(0[xX]" + HexDigits + "(\\.)?)|" +
       *
       *        // 0[xX] HexDigits_opt . HexDigits BinaryExponent FloatTypeSuffix_opt
       *        "(0[xX]" + HexDigits + "?(\\.)" + HexDigits + ")" +
       *
       *        ")[pP][+-]?" + Digits + "))" +
       *       "[fFdD]?))" +
       *       "[\\x00-\\x20]*");// Optional trailing "whitespace"
       *
       *  if (Pattern.matches(fpRegex, myString))
       *      Double.valueOf(myString); // Will not throw NumberFormatException
       *  else {
       *      // Perform suitable alternative action
       *  }
       * }</pre>
       *
       * @param      s   the string to be parsed.
       * @return     a {@code Double} object holding the value
       *             represented by the {@code String} argument.
       * @throws     NumberFormatException  if the string does not contain a
       *             parsable number.
       */
      public static Double valueOf(String s) throws NumberFormatException {
          return new Double(parseDouble(s));
      }
  
      /**
       * Returns a {@code Double} instance representing the specified
       * {@code double} value.
       * If a new {@code Double} instance is not required, this method
       * should generally be used in preference to the constructor
       * {@link #Double(double)}, as this method is likely to yield
       * significantly better space and time performance by caching
       * frequently requested values.
       *
       * @param  d a double value.
       * @return a {@code Double} instance representing {@code d}.
       * @since  1.5
       */
      public static Double valueOf(double d) {
          return new Double(d);
      }
  
      /**
       * Returns a new {@code double} initialized to the value
       * represented by the specified {@code String}, as performed
       * by the {@code valueOf} method of class
       * {@code Double}.
       *
       * @param  s   the string to be parsed.
       * @return the {@code double} value represented by the string
       *         argument.
       * @throws NullPointerException  if the string is null
       * @throws NumberFormatException if the string does not contain
       *         a parsable {@code double}.
       * @see    Double#valueOf(String)
       * @since 1.2
       */
      public static double parseDouble(String s) throws NumberFormatException {
          return FloatingDecimal.parseDouble(s);
      }
  
      /**
       * Returns {@code true} if the specified number is a
       * Not-a-Number (NaN) value, {@code false} otherwise.
       *
       * @param   v   the value to be tested.
       * @return  {@code true} if the value of the argument is NaN;
       *          {@code false} otherwise.
       */
      public static boolean isNaN(double v) {
          return (v != v);
      }
  
      /**
       * Returns {@code true} if the specified number is infinitely
       * large in magnitude, {@code false} otherwise.
       *
       * @param   v   the value to be tested.
       * @return  {@code true} if the value of the argument is positive
       *          infinity or negative infinity; {@code false} otherwise.
       */
      public static boolean isInfinite(double v) {
          return (v == POSITIVE_INFINITY) || (v == NEGATIVE_INFINITY);
      }
  
      /**
       * Returns {@code true} if the argument is a finite floating-point
       * value; returns {@code false} otherwise (for NaN and infinity
       * arguments).
       *
       * @param d the {@code double} value to be tested
       * @return {@code true} if the argument is a finite
       * floating-point value, {@code false} otherwise.
       * @since 1.8
       */
      public static boolean isFinite(double d) {
          return Math.abs(d) <= DoubleConsts.MAX_VALUE;
      }
  
      /**
       * The value of the Double.
       *
       * @serial
       */
      private final double value;
  
      /**
       * Constructs a newly allocated {@code Double} object that
       * represents the primitive {@code double} argument.
       *
       * @param   value   the value to be represented by the {@code Double}.
       */
      public Double(double value) {
          this.value = value;
      }
  
      /**
       * Constructs a newly allocated {@code Double} object that
       * represents the floating-point value of type {@code double}
       * represented by the string. The string is converted to a
       * {@code double} value as if by the {@code valueOf} method.
       *
       * @param  s  a string to be converted to a {@code Double}.
       * @throws    NumberFormatException  if the string does not contain a
       *            parsable number.
       * @see       Double#valueOf(String)
       */
      public Double(String s) throws NumberFormatException {
          value = parseDouble(s);
      }
  
      /**
       * Returns {@code true} if this {@code Double} value is
       * a Not-a-Number (NaN), {@code false} otherwise.
       *
       * @return  {@code true} if the value represented by this object is
       *          NaN; {@code false} otherwise.
       */
      public boolean isNaN() {
          return isNaN(value);
      }
  
      /**
       * Returns {@code true} if this {@code Double} value is
       * infinitely large in magnitude, {@code false} otherwise.
       *
       * @return  {@code true} if the value represented by this object is
       *          positive infinity or negative infinity;
       *          {@code false} otherwise.
       */
      public boolean isInfinite() {
          return isInfinite(value);
      }
  
      /**
       * Returns a string representation of this {@code Double} object.
       * The primitive {@code double} value represented by this
       * object is converted to a string exactly as if by the method
       * {@code toString} of one argument.
       *
       * @return  a {@code String} representation of this object.
       * @see Double#toString(double)
       */
      public String toString() {
          return toString(value);
      }
  
      /**
       * Returns the value of this {@code Double} as a {@code byte}
       * after a narrowing primitive conversion.
       *
       * @return  the {@code double} value represented by this object
       *          converted to type {@code byte}
       * @jls 5.1.3 Narrowing Primitive Conversions
       * @since JDK1.1
       */
      public byte byteValue() {
          return (byte)value;
      }
  
      /**
       * Returns the value of this {@code Double} as a {@code short}
       * after a narrowing primitive conversion.
       *
       * @return  the {@code double} value represented by this object
       *          converted to type {@code short}
       * @jls 5.1.3 Narrowing Primitive Conversions
       * @since JDK1.1
       */
      public short shortValue() {
          return (short)value;
      }
  
      /**
       * Returns the value of this {@code Double} as an {@code int}
       * after a narrowing primitive conversion.
       * @jls 5.1.3 Narrowing Primitive Conversions
       *
       * @return  the {@code double} value represented by this object
       *          converted to type {@code int}
       */
      public int intValue() {
          return (int)value;
      }
  
      /**
       * Returns the value of this {@code Double} as a {@code long}
       * after a narrowing primitive conversion.
       *
       * @return  the {@code double} value represented by this object
       *          converted to type {@code long}
       * @jls 5.1.3 Narrowing Primitive Conversions
       */
      public long longValue() {
          return (long)value;
      }
  
      /**
       * Returns the value of this {@code Double} as a {@code float}
       * after a narrowing primitive conversion.
       *
       * @return  the {@code double} value represented by this object
       *          converted to type {@code float}
       * @jls 5.1.3 Narrowing Primitive Conversions
       * @since JDK1.0
       */
      public float floatValue() {
          return (float)value;
      }
  
      /**
       * Returns the {@code double} value of this {@code Double} object.
       *
       * @return the {@code double} value represented by this object
       */
      public double doubleValue() {
          return value;
      }
  
      /**
       * Returns a hash code for this {@code Double} object. The
       * result is the exclusive OR of the two halves of the
       * {@code long} integer bit representation, exactly as
       * produced by the method {@link #doubleToLongBits(double)}, of
       * the primitive {@code double} value represented by this
       * {@code Double} object. That is, the hash code is the value
       * of the expression:
       *
       * <blockquote>
       *  {@code (int)(v^(v>>>32))}
       * </blockquote>
       *
       * where {@code v} is defined by:
       *
       * <blockquote>
       *  {@code long v = Double.doubleToLongBits(this.doubleValue());}
       * </blockquote>
       *
       * @return  a {@code hash code} value for this object.
       */
      @Override
      public int hashCode() {
          return Double.hashCode(value);
      }
  
      /**
       * Returns a hash code for a {@code double} value; compatible with
       * {@code Double.hashCode()}.
       *
       * @param value the value to hash
       * @return a hash code value for a {@code double} value.
       * @since 1.8
       */
      public static int hashCode(double value) {
          long bits = doubleToLongBits(value);
          return (int)(bits ^ (bits >>> 32));
      }
  
      /**
       * Compares this object against the specified object.  The result
       * is {@code true} if and only if the argument is not
       * {@code null} and is a {@code Double} object that
       * represents a {@code double} that has the same value as the
       * {@code double} represented by this object. For this
       * purpose, two {@code double} values are considered to be
       * the same if and only if the method {@link
       * #doubleToLongBits(double)} returns the identical
       * {@code long} value when applied to each.
       *
       * <p>Note that in most cases, for two instances of class
       * {@code Double}, {@code d1} and {@code d2}, the
       * value of {@code d1.equals(d2)} is {@code true} if and
       * only if
       *
       * <blockquote>
       *  {@code d1.doubleValue() == d2.doubleValue()}
       * </blockquote>
       *
       * <p>also has the value {@code true}. However, there are two
       * exceptions:
       * <ul>
       * <li>If {@code d1} and {@code d2} both represent
       *     {@code Double.NaN}, then the {@code equals} method
       *     returns {@code true}, even though
       *     {@code Double.NaN==Double.NaN} has the value
       *     {@code false}.
       * <li>If {@code d1} represents {@code +0.0} while
       *     {@code d2} represents {@code -0.0}, or vice versa,
       *     the {@code equal} test has the value {@code false},
       *     even though {@code +0.0==-0.0} has the value {@code true}.
       * </ul>
       * This definition allows hash tables to operate properly.
       * @param   obj   the object to compare with.
       * @return  {@code true} if the objects are the same;
       *          {@code false} otherwise.
       * @see Double#doubleToLongBits(double)
       */
      public boolean equals(Object obj) {
          return (obj instanceof Double)
                 && (doubleToLongBits(((Double)obj).value) ==
                        doubleToLongBits(value));
      }
  
      /**
       * Returns a representation of the specified floating-point value
       * according to the IEEE 754 floating-point "double
       * format" bit layout.
       *
       * <p>Bit 63 (the bit that is selected by the mask
       * {@code 0x8000000000000000L}) represents the sign of the
       * floating-point number. Bits
       * 62-52 (the bits that are selected by the mask
       * {@code 0x7ff0000000000000L}) represent the exponent. Bits 51-0
       * (the bits that are selected by the mask
       * {@code 0x000fffffffffffffL}) represent the significand
       * (sometimes called the mantissa) of the floating-point number.
       *
       * <p>If the argument is positive infinity, the result is
       * {@code 0x7ff0000000000000L}.
       *
       * <p>If the argument is negative infinity, the result is
       * {@code 0xfff0000000000000L}.
       *
       * <p>If the argument is NaN, the result is
       * {@code 0x7ff8000000000000L}.
       *
       * <p>In all cases, the result is a {@code long} integer that, when
       * given to the {@link #longBitsToDouble(long)} method, will produce a
       * floating-point value the same as the argument to
       * {@code doubleToLongBits} (except all NaN values are
       * collapsed to a single "canonical" NaN value).
       *
       * @param   value   a {@code double} precision floating-point number.
       * @return the bits that represent the floating-point number.
       */
      public static long doubleToLongBits(double value) {
          long result = doubleToRawLongBits(value);
          // Check for NaN based on values of bit fields, maximum
          // exponent and nonzero significand.
          if ( ((result & DoubleConsts.EXP_BIT_MASK) ==
                DoubleConsts.EXP_BIT_MASK) &&
               (result & DoubleConsts.SIGNIF_BIT_MASK) != 0L)
              result = 0x7ff8000000000000L;
          return result;
      }
  
      /**
       * Returns a representation of the specified floating-point value
       * according to the IEEE 754 floating-point "double
       * format" bit layout, preserving Not-a-Number (NaN) values.
       *
       * <p>Bit 63 (the bit that is selected by the mask
       * {@code 0x8000000000000000L}) represents the sign of the
       * floating-point number. Bits
       * 62-52 (the bits that are selected by the mask
       * {@code 0x7ff0000000000000L}) represent the exponent. Bits 51-0
       * (the bits that are selected by the mask
       * {@code 0x000fffffffffffffL}) represent the significand
       * (sometimes called the mantissa) of the floating-point number.
       *
       * <p>If the argument is positive infinity, the result is
       * {@code 0x7ff0000000000000L}.
       *
       * <p>If the argument is negative infinity, the result is
       * {@code 0xfff0000000000000L}.
       *
       * <p>If the argument is NaN, the result is the {@code long}
       * integer representing the actual NaN value.  Unlike the
       * {@code doubleToLongBits} method,
       * {@code doubleToRawLongBits} does not collapse all the bit
       * patterns encoding a NaN to a single "canonical" NaN
       * value.
       *
       * <p>In all cases, the result is a {@code long} integer that,
       * when given to the {@link #longBitsToDouble(long)} method, will
       * produce a floating-point value the same as the argument to
       * {@code doubleToRawLongBits}.
       *
       * @param   value   a {@code double} precision floating-point number.
       * @return the bits that represent the floating-point number.
       * @since 1.3
       */
      public static native long doubleToRawLongBits(double value);
  
      /**
       * Returns the {@code double} value corresponding to a given
       * bit representation.
       * The argument is considered to be a representation of a
       * floating-point value according to the IEEE 754 floating-point
       * "double format" bit layout.
       *
       * <p>If the argument is {@code 0x7ff0000000000000L}, the result
       * is positive infinity.
       *
       * <p>If the argument is {@code 0xfff0000000000000L}, the result
       * is negative infinity.
       *
       * <p>If the argument is any value in the range
       * {@code 0x7ff0000000000001L} through
       * {@code 0x7fffffffffffffffL} or in the range
       * {@code 0xfff0000000000001L} through
       * {@code 0xffffffffffffffffL}, the result is a NaN.  No IEEE
       * 754 floating-point operation provided by Java can distinguish
       * between two NaN values of the same type with different bit
       * patterns.  Distinct values of NaN are only distinguishable by
       * use of the {@code Double.doubleToRawLongBits} method.
       *
       * <p>In all other cases, let <i>s</i>, <i>e</i>, and <i>m</i> be three
       * values that can be computed from the argument:
       *
       * <blockquote><pre>{@code
       * int s = ((bits >> 63) == 0) ? 1 : -1;
       * int e = (int)((bits >> 52) & 0x7ffL);
       * long m = (e == 0) ?
       *                 (bits & 0xfffffffffffffL) << 1 :
       *                 (bits & 0xfffffffffffffL) | 0x10000000000000L;
       * }</pre></blockquote>
       *
       * Then the floating-point result equals the value of the mathematical
       * expression <i>s</i>&middot;<i>m</i>&middot;2<sup><i>e</i>-1075</sup>.
       *
       * <p>Note that this method may not be able to return a
       * {@code double} NaN with exactly same bit pattern as the
       * {@code long} argument.  IEEE 754 distinguishes between two
       * kinds of NaNs, quiet NaNs and <i>signaling NaNs</i>.  The
       * differences between the two kinds of NaN are generally not
       * visible in Java.  Arithmetic operations on signaling NaNs turn
       * them into quiet NaNs with a different, but often similar, bit
       * pattern.  However, on some processors merely copying a
       * signaling NaN also performs that conversion.  In particular,
       * copying a signaling NaN to return it to the calling method
       * may perform this conversion.  So {@code longBitsToDouble}
       * may not be able to return a {@code double} with a
       * signaling NaN bit pattern.  Consequently, for some
       * {@code long} values,
       * {@code doubleToRawLongBits(longBitsToDouble(start))} may
       * <i>not</i> equal {@code start}.  Moreover, which
       * particular bit patterns represent signaling NaNs is platform
       * dependent; although all NaN bit patterns, quiet or signaling,
       * must be in the NaN range identified above.
       *
       * @param   bits   any {@code long} integer.
       * @return  the {@code double} floating-point value with the same
       *          bit pattern.
       */
      public static native double longBitsToDouble(long bits);
  
      /**
       * Compares two {@code Double} objects numerically.  There
       * are two ways in which comparisons performed by this method
       * differ from those performed by the Java language numerical
       * comparison operators ({@code <, <=, ==, >=, >})
       * when applied to primitive {@code double} values:
       * <ul><li>
       *          {@code Double.NaN} is considered by this method
       *          to be equal to itself and greater than all other
       *          {@code double} values (including
       *          {@code Double.POSITIVE_INFINITY}).
       * <li>
       *          {@code 0.0d} is considered by this method to be greater
       *          than {@code -0.0d}.
       * </ul>
       * This ensures that the <i>natural ordering</i> of
       * {@code Double} objects imposed by this method is <i>consistent
       * with equals</i>.
       *
       * @param   anotherDouble   the {@code Double} to be compared.
       * @return  the value {@code 0} if {@code anotherDouble} is
       *          numerically equal to this {@code Double}; a value
       *          less than {@code 0} if this {@code Double}
       *          is numerically less than {@code anotherDouble};
       *          and a value greater than {@code 0} if this
       *          {@code Double} is numerically greater than
       *          {@code anotherDouble}.
       *
       * @since   1.2
       */
      public int compareTo(Double anotherDouble) {
          return Double.compare(value, anotherDouble.value);
      }
  
      /**
       * Compares the two specified {@code double} values. The sign
       * of the integer value returned is the same as that of the
       * integer that would be returned by the call:
       * <pre>
       *    new Double(d1).compareTo(new Double(d2))
       * </pre>
       *
       * @param   d1        the first {@code double} to compare
       * @param   d2        the second {@code double} to compare
       * @return  the value {@code 0} if {@code d1} is
       *          numerically equal to {@code d2}; a value less than
       *          {@code 0} if {@code d1} is numerically less than
       *          {@code d2}; and a value greater than {@code 0}
       *          if {@code d1} is numerically greater than
       *          {@code d2}.
       * @since 1.4
       */
      public static int compare(double d1, double d2) {
          if (d1 < d2)
              return -1;           // Neither val is NaN, thisVal is smaller
          if (d1 > d2)
              return 1;            // Neither val is NaN, thisVal is larger
  
          // Cannot use doubleToRawLongBits because of possibility of NaNs.
          long thisBits    = Double.doubleToLongBits(d1);
          long anotherBits = Double.doubleToLongBits(d2);
  
          return (thisBits == anotherBits ?  0 : // Values are equal
                  (thisBits < anotherBits ? -1 : // (-0.0, 0.0) or (!NaN, NaN)
                   1));                          // (0.0, -0.0) or (NaN, !NaN)
      }
  
      /**
       * Adds two {@code double} values together as per the + operator.
       *
       * @param a the first operand
       * @param b the second operand
       * @return the sum of {@code a} and {@code b}
       * @jls 4.2.4 Floating-Point Operations
       * @see java.util.function.BinaryOperator
       * @since 1.8
       */
      public static double sum(double a, double b) {
          return a + b;
      }
  
      /**
       * Returns the greater of two {@code double} values
       * as if by calling {@link Math#max(double, double) Math.max}.
       *
       * @param a the first operand
       * @param b the second operand
       * @return the greater of {@code a} and {@code b}
       * @see java.util.function.BinaryOperator
       * @since 1.8
       */
      public static double max(double a, double b) {
          return Math.max(a, b);
      }
  
      /**
       * Returns the smaller of two {@code double} values
       * as if by calling {@link Math#min(double, double) Math.min}.
       *
       * @param a the first operand
       * @param b the second operand
       * @return the smaller of {@code a} and {@code b}.
       * @see java.util.function.BinaryOperator
       * @since 1.8
       */
      public static double min(double a, double b) {
          return Math.min(a, b);
      }
  
      /** use serialVersionUID from JDK 1.0.2 for interoperability */
      private static final long serialVersionUID = -9172774392245257468L;
  }
  