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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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 */

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><h3>Examples</h3></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>

     *

     * <p>

     *

     * <dl>

     * <dt><i>HexFloatingPointLiteral</i>:

     * <dd> <i>HexSignificand BinaryExponent FloatTypeSuffix<sub>opt</sub></i>

     * </dl>

     *

     * <p>

     *

     * <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>

     *

     * <p>

     *

     * <dl>

     * <dt><i>BinaryExponent:</i>

     * <dd><i>BinaryExponentIndicator SignedInteger</i>

     * </dl>

     *

     * <p>

     *

     * <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:

     *

     * <code>

     * <pre>

     *  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

     *       // <cite>The Java&trade; Language Specification</cite>.

     *

     *       // 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>

     * </code>

     *

     * @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.