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 * Copyright (c) 1994, 2019, 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 java.lang.annotation.Native;

import java.lang.invoke.MethodHandles;

import java.lang.constant.Constable;

import java.lang.constant.ConstantDesc;

import java.util.Objects;

import java.util.Optional;

import jdk.internal.HotSpotIntrinsicCandidate;

import jdk.internal.misc.VM;

import static java.lang.String.COMPACT_STRINGS;

import static java.lang.String.LATIN1;

import static java.lang.String.UTF16;

/**

 * The {@code Integer} class wraps a value of the primitive type

 * {@code int} in an object. An object of type {@code Integer}

 * contains a single field whose type is {@code int}.

 *

 * <p>In addition, this class provides several methods for converting

 * an {@code int} to a {@code String} and a {@code String} to an

 * {@code int}, as well as other constants and methods useful when

 * dealing with an {@code int}.

 *

 * <p>Implementation note: The implementations of the "bit twiddling"

 * methods (such as {@link #highestOneBit(int) highestOneBit} and

 * {@link #numberOfTrailingZeros(int) numberOfTrailingZeros}) are

 * based on material from Henry S. Warren, Jr.'s <i>Hacker's

 * Delight</i>, (Addison Wesley, 2002).

 *

 * @author  Lee Boynton

 * @author  Arthur van Hoff

 * @author  Josh Bloch

 * @author  Joseph D. Darcy

 * @since 1.0

 */

public final class Integer extends Number

        implements Comparable<Integer>, Constable, ConstantDesc {

    /**

     * A constant holding the minimum value an {@code int} can

     * have, -2<sup>31</sup>.

     */

    @Native public static final int   MIN_VALUE = 0x80000000;

    /**

     * A constant holding the maximum value an {@code int} can

     * have, 2<sup>31</sup>-1.

     */

    @Native public static final int   MAX_VALUE = 0x7fffffff;

    /**

     * The {@code Class} instance representing the primitive type

     * {@code int}.

     *

     * @since   1.1

     */

    @SuppressWarnings("unchecked")

    public static final Class<Integer>  TYPE = (Class<Integer>) Class.getPrimitiveClass("int");

    /**

     * All possible chars for representing a number as a String

     */

    static final char[] digits = {

        '0' , '1' , '2' , '3' , '4' , '5' ,

        '6' , '7' , '8' , '9' , 'a' , 'b' ,

        'c' , 'd' , 'e' , 'f' , 'g' , 'h' ,

        'i' , 'j' , 'k' , 'l' , 'm' , 'n' ,

        'o' , 'p' , 'q' , 'r' , 's' , 't' ,

        'u' , 'v' , 'w' , 'x' , 'y' , 'z'

    };

    /**

     * Returns a string representation of the first argument in the

     * radix specified by the second argument.

     *

     * <p>If the radix is smaller than {@code Character.MIN_RADIX}

     * or larger than {@code Character.MAX_RADIX}, then the radix

     * {@code 10} is used instead.

     *

     * <p>If the first argument is negative, the first element of the

     * result is the ASCII minus character {@code '-'}

     * ({@code '\u005Cu002D'}). If the first argument is not

     * negative, no sign character appears in the result.

     *

     * <p>The remaining characters of the result represent the magnitude

     * of the first argument. If the magnitude is zero, it is

     * represented by a single zero character {@code '0'}

     * ({@code '\u005Cu0030'}); otherwise, the first character of

     * the representation of the magnitude will not be the zero

     * character.  The following ASCII characters are used as digits:

     *

     * <blockquote>

     *   {@code 0123456789abcdefghijklmnopqrstuvwxyz}

     * </blockquote>

     *

     * These are {@code '\u005Cu0030'} through

     * {@code '\u005Cu0039'} and {@code '\u005Cu0061'} through

     * {@code '\u005Cu007A'}. If {@code radix} is

     * <var>N</var>, then the first <var>N</var> of these characters

     * are used as radix-<var>N</var> digits in the order shown. Thus,

     * the digits for hexadecimal (radix 16) are

     * {@code 0123456789abcdef}. If uppercase letters are

     * desired, the {@link java.lang.String#toUpperCase()} method may

     * be called on the result:

     *

     * <blockquote>

     *  {@code Integer.toString(n, 16).toUpperCase()}

     * </blockquote>

     *

     * @param   i       an integer to be converted to a string.

     * @param   radix   the radix to use in the string representation.

     * @return  a string representation of the argument in the specified radix.

     * @see     java.lang.Character#MAX_RADIX

     * @see     java.lang.Character#MIN_RADIX

     */

    public static String toString(int i, int radix) {

        if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX)

            radix = 10;

        /* Use the faster version */

        if (radix == 10) {

            return toString(i);

        }

        if (COMPACT_STRINGS) {

            byte[] buf = new byte[33];

            boolean negative = (i < 0);

            int charPos = 32;

            if (!negative) {

                i = -i;

            }

            while (i <= -radix) {

                buf[charPos--] = (byte)digits[-(i % radix)];

                i = i / radix;

            }

            buf[charPos] = (byte)digits[-i];

            if (negative) {

                buf[--charPos] = '-';

            }

            return StringLatin1.newString(buf, charPos, (33 - charPos));

        }

        return toStringUTF16(i, radix);

    }

    private static String toStringUTF16(int i, int radix) {

        byte[] buf = new byte[33 * 2];

        boolean negative = (i < 0);

        int charPos = 32;

        if (!negative) {

            i = -i;

        }

        while (i <= -radix) {

            StringUTF16.putChar(buf, charPos--, digits[-(i % radix)]);

            i = i / radix;

        }

        StringUTF16.putChar(buf, charPos, digits[-i]);

        if (negative) {

            StringUTF16.putChar(buf, --charPos, '-');

        }

        return StringUTF16.newString(buf, charPos, (33 - charPos));

    }

    /**

     * Returns a string representation of the first argument as an

     * unsigned integer value in the radix specified by the second

     * argument.

     *

     * <p>If the radix is smaller than {@code Character.MIN_RADIX}

     * or larger than {@code Character.MAX_RADIX}, then the radix

     * {@code 10} is used instead.

     *

     * <p>Note that since the first argument is treated as an unsigned

     * value, no leading sign character is printed.

     *

     * <p>If the magnitude is zero, it is represented by a single zero

     * character {@code '0'} ({@code '\u005Cu0030'}); otherwise,

     * the first character of the representation of the magnitude will

     * not be the zero character.

     *

     * <p>The behavior of radixes and the characters used as digits

     * are the same as {@link #toString(int, int) toString}.

     *

     * @param   i       an integer to be converted to an unsigned string.

     * @param   radix   the radix to use in the string representation.

     * @return  an unsigned string representation of the argument in the specified radix.

     * @see     #toString(int, int)

     * @since 1.8

     */

    public static String toUnsignedString(int i, int radix) {

        return Long.toUnsignedString(toUnsignedLong(i), radix);

    }

    /**

     * Returns a string representation of the integer argument as an

     * unsigned integer in base 16.

     *

     * <p>The unsigned integer value is the argument plus 2<sup>32</sup>

     * if the argument is negative; otherwise, it is equal to the

     * argument.  This value is converted to a string of ASCII digits

     * in hexadecimal (base 16) with no extra leading

     * {@code 0}s.

     *

     * <p>The value of the argument can be recovered from the returned

     * string {@code s} by calling {@link

     * Integer#parseUnsignedInt(String, int)

     * Integer.parseUnsignedInt(s, 16)}.

     *

     * <p>If the unsigned magnitude is zero, it is represented by a

     * single zero character {@code '0'} ({@code '\u005Cu0030'});

     * otherwise, the first character of the representation of the

     * unsigned magnitude will not be the zero character. The

     * following characters are used as hexadecimal digits:

     *

     * <blockquote>

     *  {@code 0123456789abcdef}

     * </blockquote>

     *

     * These are the characters {@code '\u005Cu0030'} through

     * {@code '\u005Cu0039'} and {@code '\u005Cu0061'} through

     * {@code '\u005Cu0066'}. If uppercase letters are

     * desired, the {@link java.lang.String#toUpperCase()} method may

     * be called on the result:

     *

     * <blockquote>

     *  {@code Integer.toHexString(n).toUpperCase()}

     * </blockquote>

     *

     * @param   i   an integer to be converted to a string.

     * @return  the string representation of the unsigned integer value

     *          represented by the argument in hexadecimal (base 16).

     * @see #parseUnsignedInt(String, int)

     * @see #toUnsignedString(int, int)

     * @since   1.0.2

     */

    public static String toHexString(int i) {

        return toUnsignedString0(i, 4);

    }

    /**

     * Returns a string representation of the integer argument as an

     * unsigned integer in base 8.

     *

     * <p>The unsigned integer value is the argument plus 2<sup>32</sup>

     * if the argument is negative; otherwise, it is equal to the

     * argument.  This value is converted to a string of ASCII digits

     * in octal (base 8) with no extra leading {@code 0}s.

     *

     * <p>The value of the argument can be recovered from the returned

     * string {@code s} by calling {@link

     * Integer#parseUnsignedInt(String, int)

     * Integer.parseUnsignedInt(s, 8)}.

     *

     * <p>If the unsigned magnitude is zero, it is represented by a

     * single zero character {@code '0'} ({@code '\u005Cu0030'});

     * otherwise, the first character of the representation of the

     * unsigned magnitude will not be the zero character. The

     * following characters are used as octal digits:

     *

     * <blockquote>

     * {@code 01234567}

     * </blockquote>

     *

     * These are the characters {@code '\u005Cu0030'} through

     * {@code '\u005Cu0037'}.

     *

     * @param   i   an integer to be converted to a string.

     * @return  the string representation of the unsigned integer value

     *          represented by the argument in octal (base 8).

     * @see #parseUnsignedInt(String, int)

     * @see #toUnsignedString(int, int)

     * @since   1.0.2

     */

    public static String toOctalString(int i) {

        return toUnsignedString0(i, 3);

    }

    /**

     * Returns a string representation of the integer argument as an

     * unsigned integer in base 2.

     *

     * <p>The unsigned integer value is the argument plus 2<sup>32</sup>

     * if the argument is negative; otherwise it is equal to the

     * argument.  This value is converted to a string of ASCII digits

     * in binary (base 2) with no extra leading {@code 0}s.

     *

     * <p>The value of the argument can be recovered from the returned

     * string {@code s} by calling {@link

     * Integer#parseUnsignedInt(String, int)

     * Integer.parseUnsignedInt(s, 2)}.

     *

     * <p>If the unsigned magnitude is zero, it is represented by a

     * single zero character {@code '0'} ({@code '\u005Cu0030'});

     * otherwise, the first character of the representation of the

     * unsigned magnitude will not be the zero character. The

     * characters {@code '0'} ({@code '\u005Cu0030'}) and {@code

     * '1'} ({@code '\u005Cu0031'}) are used as binary digits.

     *

     * @param   i   an integer to be converted to a string.

     * @return  the string representation of the unsigned integer value

     *          represented by the argument in binary (base 2).

     * @see #parseUnsignedInt(String, int)

     * @see #toUnsignedString(int, int)

     * @since   1.0.2

     */

    public static String toBinaryString(int i) {

        return toUnsignedString0(i, 1);

    }

    /**

     * Convert the integer to an unsigned number.

     */

    private static String toUnsignedString0(int val, int shift) {

        // assert shift > 0 && shift <=5 : "Illegal shift value";

        int mag = Integer.SIZE - Integer.numberOfLeadingZeros(val);

        int chars = Math.max(((mag + (shift - 1)) / shift), 1);

        if (COMPACT_STRINGS) {

            byte[] buf = new byte[chars];

            formatUnsignedInt(val, shift, buf, chars);

            return new String(buf, LATIN1);

        } else {

            byte[] buf = new byte[chars * 2];

            formatUnsignedIntUTF16(val, shift, buf, chars);

            return new String(buf, UTF16);

        }

    }

    /**

     * Format an {@code int} (treated as unsigned) into a byte buffer (LATIN1 version). If

     * {@code len} exceeds the formatted ASCII representation of {@code val},

     * {@code buf} will be padded with leading zeroes.

     *

     * @param val the unsigned int to format

     * @param shift the log2 of the base to format in (4 for hex, 3 for octal, 1 for binary)

     * @param buf the byte buffer to write to

     * @param len the number of characters to write

     */

    private static void formatUnsignedInt(int val, int shift, byte[] buf, int len) {

        int charPos = len;

        int radix = 1 << shift;

        int mask = radix - 1;

        do {

            buf[--charPos] = (byte)Integer.digits[val & mask];

            val >>>= shift;

        } while (charPos > 0);

    }

    /**

     * Format an {@code int} (treated as unsigned) into a byte buffer (UTF16 version). If

     * {@code len} exceeds the formatted ASCII representation of {@code val},

     * {@code buf} will be padded with leading zeroes.

     *

     * @param val the unsigned int to format

     * @param shift the log2 of the base to format in (4 for hex, 3 for octal, 1 for binary)

     * @param buf the byte buffer to write to

     * @param len the number of characters to write

     */

    private static void formatUnsignedIntUTF16(int val, int shift, byte[] buf, int len) {

        int charPos = len;

        int radix = 1 << shift;

        int mask = radix - 1;

        do {

            StringUTF16.putChar(buf, --charPos, Integer.digits[val & mask]);

            val >>>= shift;

        } while (charPos > 0);

    }

    static final byte[] DigitTens = {

        '0', '0', '0', '0', '0', '0', '0', '0', '0', '0',

        '1', '1', '1', '1', '1', '1', '1', '1', '1', '1',

        '2', '2', '2', '2', '2', '2', '2', '2', '2', '2',

        '3', '3', '3', '3', '3', '3', '3', '3', '3', '3',

        '4', '4', '4', '4', '4', '4', '4', '4', '4', '4',

        '5', '5', '5', '5', '5', '5', '5', '5', '5', '5',

        '6', '6', '6', '6', '6', '6', '6', '6', '6', '6',

        '7', '7', '7', '7', '7', '7', '7', '7', '7', '7',

        '8', '8', '8', '8', '8', '8', '8', '8', '8', '8',

        '9', '9', '9', '9', '9', '9', '9', '9', '9', '9',

        } ;

    static final byte[] DigitOnes = {

        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',

        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',

        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',

        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',

        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',

        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',

        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',

        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',

        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',

        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',

        } ;

    /**

     * Returns a {@code String} object representing the

     * specified integer. The argument is converted to signed decimal

     * representation and returned as a string, exactly as if the

     * argument and radix 10 were given as arguments to the {@link

     * #toString(int, int)} method.

     *

     * @param   i   an integer to be converted.

     * @return  a string representation of the argument in base 10.

     */

    @HotSpotIntrinsicCandidate

    public static String toString(int i) {

        int size = stringSize(i);

        if (COMPACT_STRINGS) {

            byte[] buf = new byte[size];

            getChars(i, size, buf);

            return new String(buf, LATIN1);

        } else {

            byte[] buf = new byte[size * 2];

            StringUTF16.getChars(i, size, buf);

            return new String(buf, UTF16);

        }

    }

    /**

     * Returns a string representation of the argument as an unsigned

     * decimal value.

     *

     * The argument is converted to unsigned decimal representation

     * and returned as a string exactly as if the argument and radix

     * 10 were given as arguments to the {@link #toUnsignedString(int,

     * int)} method.

     *

     * @param   i  an integer to be converted to an unsigned string.

     * @return  an unsigned string representation of the argument.

     * @see     #toUnsignedString(int, int)

     * @since 1.8

     */

    public static String toUnsignedString(int i) {

        return Long.toString(toUnsignedLong(i));

    }

    /**

     * Places characters representing the integer i into the

     * character array buf. The characters are placed into

     * the buffer backwards starting with the least significant

     * digit at the specified index (exclusive), and working

     * backwards from there.

     *

     * @implNote This method converts positive inputs into negative

     * values, to cover the Integer.MIN_VALUE case. Converting otherwise

     * (negative to positive) will expose -Integer.MIN_VALUE that overflows

     * integer.

     *

     * @param i     value to convert

     * @param index next index, after the least significant digit

     * @param buf   target buffer, Latin1-encoded

     * @return index of the most significant digit or minus sign, if present

     */

    static int getChars(int i, int index, byte[] buf) {

        int q, r;

        int charPos = index;

        boolean negative = i < 0;

        if (!negative) {

            i = -i;

        }

        // Generate two digits per iteration

        while (i <= -100) {

            q = i / 100;

            r = (q * 100) - i;

            i = q;

            buf[--charPos] = DigitOnes[r];

            buf[--charPos] = DigitTens[r];

        }

        // We know there are at most two digits left at this point.