/*
 * Copyright (c) 1994, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 */

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 java.lang.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 java.lang.Double#valueOf(java.lang.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 java.lang.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 java.lang.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;
}