/*

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  * 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.util.Properties;

 /**

  * 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 JDK1.0

  */

 public final class Integer extends Number implements Comparable<Integer> {

     /**

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

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

      */

     public static final int   MIN_VALUE = 0x80000000;

     /**

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

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

      */

     public static final int   MAX_VALUE = 0x7fffffff;

     /**

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

      * {@code int}.

      *

      * @since   JDK1.1

      */

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

     /**

      * All possible chars for representing a number as a String

      */

     final static 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>'&#92;u002D'</code>). 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>'&#92;u0030'</code>); 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>'&#92;u0030'</code> through

      * <code>'&#92;u0039'</code> and <code>'&#92;u0061'</code> through

      * <code>'&#92;u007A'</code>. 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);

         }

         char buf[] = new char[33];

         boolean negative = (i < 0);

         int charPos = 32;

         if (!negative) {

             i = -i;

         }

         while (i <= -radix) {

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

             i = i / radix;

         }

         buf[charPos] = digits[-i];

         if (negative) {

             buf[--charPos] = '-';

         }

         return new String(buf, charPos, (33 - charPos));

     }

     /**

      * 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. If the unsigned magnitude is zero, it is

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

      * (<code>'&#92;u0030'</code>); 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>'&#92;u0030'</code> through

      * <code>'&#92;u0039'</code> and <code>'&#92;u0061'</code> through

      * <code>'&#92;u0066'</code>. 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).

      * @since   JDK1.0.2

      */

     public static String toHexString(int i) {

         return toUnsignedString(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>If the unsigned magnitude is zero, it is represented by a

      * single zero character {@code '0'}

      * (<code>'&#92;u0030'</code>); 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>'&#92;u0030'</code> through

      * <code>'&#92;u0037'</code>.

      *

      * @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).

      * @since   JDK1.0.2

      */

     public static String toOctalString(int i) {

         return toUnsignedString(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.

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

      * single zero character {@code '0'}

      * (<code>'&#92;u0030'</code>); otherwise, the first character of

      * the representation of the unsigned magnitude will not be the

      * zero character. The characters {@code '0'}

      * (<code>'&#92;u0030'</code>) and {@code '1'}

      * (<code>'&#92;u0031'</code>) 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).

      * @since   JDK1.0.2

      */

     public static String toBinaryString(int i) {

         return toUnsignedString(i, 1);

     }

     /**

      * Convert the integer to an unsigned number.

      */

     private static String toUnsignedString(int i, int shift) {

         char[] buf = new char[32];

         int charPos = 32;

         int radix = 1 << shift;

         int mask = radix - 1;

         do {

             buf[--charPos] = digits[i & mask];

             i >>>= shift;

         } while (i != 0);

         return new String(buf, charPos, (32 - charPos));

     }

     final static char [] 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',

         } ;

     final static char [] 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',

         } ;

         // I use the "invariant division by multiplication" trick to

         // accelerate Integer.toString.  In particular we want to

         // avoid division by 10.

         //

         // The "trick" has roughly the same performance characteristics

         // as the "classic" Integer.toString code on a non-JIT VM.

         // The trick avoids .rem and .div calls but has a longer code

         // path and is thus dominated by dispatch overhead.  In the

         // JIT case the dispatch overhead doesn't exist and the

         // "trick" is considerably faster than the classic code.

         //

         // TODO-FIXME: convert (x * 52429) into the equiv shift-add

         // sequence.

         //

         // RE:  Division by Invariant Integers using Multiplication

         //      T Gralund, P Montgomery

         //      ACM PLDI 1994

         //

     /**

      * 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.

      */

     public static String toString(int i) {

         if (i == Integer.MIN_VALUE)

             return "-2147483648";

         int size = (i < 0) ? stringSize(-i) + 1 : stringSize(i);

         char[] buf = new char[size];

         getChars(i, size, buf);

         return new String(0, size, buf);

     }

     /**

      * 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.

      *

      * Will fail if i == Integer.MIN_VALUE

      */

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

         int q, r;

         int charPos = index;

         char sign = 0;

         if (i < 0) {

             sign = '-';

             i = -i;

         }

         // Generate two digits per iteration

         while (i >= 65536) {

             q = i / 100;

         // really: r = i - (q * 100);

             r = i - ((q << 6) + (q << 5) + (q << 2));

             i = q;

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

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

         }

         // Fall thru to fast mode for smaller numbers

         // assert(i <= 65536, i);

         for (;;) {

             q = (i * 52429) >>> (16+3);

             r = i - ((q << 3) + (q << 1));  // r = i-(q*10) ...

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

             i = q;

             if (i == 0) break;

         }

         if (sign != 0) {

             buf [--charPos] = sign;

         }

     }

     final static int [] sizeTable = { 9, 99, 999, 9999, 99999, 999999, 9999999,

                                       99999999, 999999999, Integer.MAX_VALUE };

     // Requires positive x

     static int stringSize(int x) {

         for (int i=0; ; i++)

             if (x <= sizeTable[i])

                 return i+1;

     }

     /**

      * Parses the string argument as a signed integer in the radix

      * specified by the second argument. The characters in the string

      * must all be digits of the specified radix (as determined by

      * whether {@link java.lang.Character#digit(char, int)} returns a

      * nonnegative value), except that the first character may be an

      * ASCII minus sign {@code '-'} (<code>'&#92;u002D'</code>) to

      * indicate a negative value or an ASCII plus sign {@code '+'}

      * (<code>'&#92;u002B'</code>) to indicate a positive value. The

      * resulting integer value is returned.

      *

      * <p>An exception of type {@code NumberFormatException} is

      * thrown if any of the following situations occurs:

      * <ul>

      * <li>The first argument is {@code null} or is a string of

      * length zero.

      *

      * <li>The radix is either smaller than

      * {@link java.lang.Character#MIN_RADIX} or

      * larger than {@link java.lang.Character#MAX_RADIX}.

      *

      * <li>Any character of the string is not a digit of the specified

      * radix, except that the first character may be a minus sign

      * {@code '-'} (<code>'&#92;u002D'</code>) or plus sign

      * {@code '+'} (<code>'&#92;u002B'</code>) provided that the

      * string is longer than length 1.

      *

      * <li>The value represented by the string is not a value of type

      * {@code int}.

      * </ul>

      *

      * <p>Examples:

      * <blockquote><pre>

      * parseInt("0", 10) returns 0

      * parseInt("473", 10) returns 473

      * parseInt("+42", 10) returns 42

      * parseInt("-0", 10) returns 0

      * parseInt("-FF", 16) returns -255

      * parseInt("1100110", 2) returns 102

      * parseInt("2147483647", 10) returns 2147483647

      * parseInt("-2147483648", 10) returns -2147483648

      * parseInt("2147483648", 10) throws a NumberFormatException

      * parseInt("99", 8) throws a NumberFormatException

      * parseInt("Kona", 10) throws a NumberFormatException

      * parseInt("Kona", 27) returns 411787

      * </pre></blockquote>

      *

      * @param      s   the {@code String} containing the integer

      *                  representation to be parsed

      * @param      radix   the radix to be used while parsing {@code s}.

      * @return     the integer represented by the string argument in the

      *             specified radix.

      * @exception  NumberFormatException if the {@code String}

      *             does not contain a parsable {@code int}.

      */

     public static int parseInt(String s, int radix)

                 throws NumberFormatException

     {

         /*

          * WARNING: This method may be invoked early during VM initialization

          * before IntegerCache is initialized. Care must be taken to not use

          * the valueOf method.

          */

         if (s == null) {

             throw new NumberFormatException("null");

         }

         if (radix < Character.MIN_RADIX) {

             throw new NumberFormatException("radix " + radix +

                                             " less than Character.MIN_RADIX");

         }

         if (radix > Character.MAX_RADIX) {

             throw new NumberFormatException("radix " + radix +

                                             " greater than Character.MAX_RADIX");

         }

         int result = 0;

         boolean negative = false;

         int i = 0, len = s.length();

         int limit = -Integer.MAX_VALUE;

         int multmin;

         int digit;

         if (len > 0) {

             char firstChar = s.charAt(0);

             if (firstChar < '0') { // Possible leading "+" or "-"

                 if (firstChar == '-') {

                     negative = true;

                     limit = Integer.MIN_VALUE;

                 } else if (firstChar != '+')

                     throw NumberFormatException.forInputString(s);

                 if (len == 1) // Cannot have lone "+" or "-"

                     throw NumberFormatException.forInputString(s);

                 i++;

             }

             multmin = limit / radix;

             while (i < len) {

                 // Accumulating negatively avoids surprises near MAX_VALUE

                 digit = Character.digit(s.charAt(i++),radix);

                 if (digit < 0) {

                     throw NumberFormatException.forInputString(s);

                 }

                 if (result < multmin) {

                     throw NumberFormatException.forInputString(s);

                 }

                 result *= radix;

                 if (result < limit + digit) {

                     throw NumberFormatException.forInputString(s);

                 }

                 result -= digit;

             }

         } else {

             throw NumberFormatException.forInputString(s);

         }

         return negative ? result : -result;

     }

     /**

      * Parses the string argument as a signed decimal integer. The

      * characters in the string must all be decimal digits, except

      * that the first character may be an ASCII minus sign {@code '-'}

      * (<code>'&#92;u002D'</code>) to indicate a negative value or an

      * ASCII plus sign {@code '+'} (<code>'&#92;u002B'</code>) to

      * indicate a positive value. The resulting integer value is

      * returned, exactly as if the argument and the radix 10 were

      * given as arguments to the {@link #parseInt(java.lang.String,

      * int)} method.

      *

      * @param s    a {@code String} containing the {@code int}

      *             representation to be parsed

      * @return     the integer value represented by the argument in decimal.

      * @exception  NumberFormatException  if the string does not contain a

      *               parsable integer.

      */

     public static int parseInt(String s) throws NumberFormatException {

         return parseInt(s,10);

     }

     /**

      * Returns an {@code Integer} object holding the value

      * extracted from the specified {@code String} when parsed

      * with the radix given by the second argument. The first argument

      * is interpreted as representing a signed integer in the radix

      * specified by the second argument, exactly as if the arguments

      * were given to the {@link #parseInt(java.lang.String, int)}

      * method. The result is an {@code Integer} object that

      * represents the integer value specified by the string.

      *

      * <p>In other words, this method returns an {@code Integer}

      * object equal to the value of:

      *

      * <blockquote>

      *  {@code new Integer(Integer.parseInt(s, radix))}

      * </blockquote>

      *

      * @param      s   the string to be parsed.

      * @param      radix the radix to be used in interpreting {@code s}

      * @return     an {@code Integer} object holding the value

      *             represented by the string argument in the specified

      *             radix.

      * @exception NumberFormatException if the {@code String}

      *            does not contain a parsable {@code int}.

      */

     public static Integer valueOf(String s, int radix) throws NumberFormatException {

         return Integer.valueOf(parseInt(s,radix));

     }

     /**

      * Returns an {@code Integer} object holding the

      * value of the specified {@code String}. The argument is

      * interpreted as representing a signed decimal integer, exactly

      * as if the argument were given to the {@link

      * #parseInt(java.lang.String)} method. The result is an

      * {@code Integer} object that represents the integer value

      * specified by the string.

      *

      * <p>In other words, this method returns an {@code Integer}

      * object equal to the value of:

      *

      * <blockquote>

      *  {@code new Integer(Integer.parseInt(s))}

      * </blockquote>

      *

      * @param      s   the string to be parsed.

      * @return     an {@code Integer} object holding the value

      *             represented by the string argument.

      * @exception  NumberFormatException  if the string cannot be parsed

      *             as an integer.

      */

     public static Integer valueOf(String s) throws NumberFormatException {

         return Integer.valueOf(parseInt(s, 10));

     }

     /**

      * Cache to support the object identity semantics of autoboxing for values between

      * -128 and 127 (inclusive) as required by JLS.

      *

      * The cache is initialized on first usage.  The size of the cache

      * may be controlled by the -XX:AutoBoxCacheMax=<size> option.

      * During VM initialization, java.lang.Integer.IntegerCache.high property

      * may be set and saved in the private system properties in the

      * sun.misc.VM class.

      */

     private static class IntegerCache {

         static final int low = -128;

         static final int high;

         static final Integer cache[];

         static {

             // high value may be configured by property

             int h = 127;

             String integerCacheHighPropValue =

                 sun.misc.VM.getSavedProperty("java.lang.Integer.IntegerCache.high");

             if (integerCacheHighPropValue != null) {

                 int i = parseInt(integerCacheHighPropValue);

                 i = Math.max(i, 127);

                 // Maximum array size is Integer.MAX_VALUE

                 h = Math.min(i, Integer.MAX_VALUE - (-low));

             }

             high = h;

             cache = new Integer[(high - low) + 1];

             int j = low;

             for(int k = 0; k < cache.length; k++)

                 cache[k] = new Integer(j++);

         }

         private IntegerCache() {}

     }

     /**

      * Returns an {@code Integer} instance representing the specified

      * {@code int} value.  If a new {@code Integer} instance is not

      * required, this method should generally be used in preference to

      * the constructor {@link #Integer(int)}, as this method is likely

      * to yield significantly better space and time performance by

      * caching frequently requested values.

      *

      * This method will always cache values in the range -128 to 127,

      * inclusive, and may cache other values outside of this range.

      *

      * @param  i an {@code int} value.

      * @return an {@code Integer} instance representing {@code i}.

      * @since  1.5

      */

     public static Integer valueOf(int i) {

         assert IntegerCache.high >= 127;

         if (i >= IntegerCache.low && i <= IntegerCache.high)

             return IntegerCache.cache[i + (-IntegerCache.low)];

         return new Integer(i);

     }

     /**

      * The value of the {@code Integer}.

      *

      * @serial

      */

     private final int value;

     /**

      * Constructs a newly allocated {@code Integer} object that

      * represents the specified {@code int} value.

      *

      * @param   value   the value to be represented by the

      *                  {@code Integer} object.

      */

     public Integer(int value) {

         this.value = value;

     }

     /**

      * Constructs a newly allocated {@code Integer} object that

      * represents the {@code int} value indicated by the

      * {@code String} parameter. The string is converted to an

      * {@code int} value in exactly the manner used by the

      * {@code parseInt} method for radix 10.

      *

      * @param      s   the {@code String} to be converted to an

      *                 {@code Integer}.

      * @exception  NumberFormatException  if the {@code String} does not

      *               contain a parsable integer.

      * @see        java.lang.Integer#parseInt(java.lang.String, int)

      */

     public Integer(String s) throws NumberFormatException {

         this.value = parseInt(s, 10);

     }

     /**

      * Returns the value of this {@code Integer} as a

      * {@code byte}.

      */

     public byte byteValue() {

         return (byte)value;

     }

     /**

      * Returns the value of this {@code Integer} as a

      * {@code short}.

      */

     public short shortValue() {

         return (short)value;

     }

     /**

      * Returns the value of this {@code Integer} as an

      * {@code int}.

      */

     public int intValue() {

         return value;

     }

     /**

      * Returns the value of this {@code Integer} as a

      * {@code long}.

      */

     public long longValue() {

         return (long)value;

     }

     /**

      * Returns the value of this {@code Integer} as a

      * {@code float}.

      */

     public float floatValue() {

         return (float)value;

     }

     /**

      * Returns the value of this {@code Integer} as a

      * {@code double}.

      */

     public double doubleValue() {

         return (double)value;

     }

     /**

      * Returns a {@code String} object representing this

      * {@code Integer}'s value. The value is converted to signed

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

      * the integer value were given as an argument to the {@link

      * java.lang.Integer#toString(int)} method.

      *

      * @return  a string representation of the value of this object in

      *          base 10.

      */

     public String toString() {

         return toString(value);

     }

     /**

      * Returns a hash code for this {@code Integer}.

      *

      * @return  a hash code value for this object, equal to the

      *          primitive {@code int} value represented by this

      *          {@code Integer} object.

      */

     public int hashCode() {

         return value;

     }

     /**

      * Compares this object to the specified object.  The result is

      * {@code true} if and only if the argument is not

      * {@code null} and is an {@code Integer} object that

      * contains the same {@code int} value as this object.

      *

      * @param   obj   the object to compare with.

      * @return  {@code true} if the objects are the same;

      *          {@code false} otherwise.

      */

     public boolean equals(Object obj) {

         if (obj instanceof Integer) {

             return value == ((Integer)obj).intValue();

         }

         return false;

     }

     /**

      * Determines the integer value of the system property with the

      * specified name.

      *

      * <p>The first argument is treated as the name of a system property.

      * System properties are accessible through the

      * {@link java.lang.System#getProperty(java.lang.String)} method. The

      * string value of this property is then interpreted as an integer

      * value and an {@code Integer} object representing this value is

      * returned. Details of possible numeric formats can be found with

      * the definition of {@code getProperty}.

      *

      * <p>If there is no property with the specified name, if the specified name

      * is empty or {@code null}, or if the property does not have

      * the correct numeric format, then {@code null} is returned.

      *

      * <p>In other words, this method returns an {@code Integer}

      * object equal to the value of:

      *

      * <blockquote>

      *  {@code getInteger(nm, null)}

      * </blockquote>

      *

      * @param   nm   property name.

      * @return  the {@code Integer} value of the property.

      * @see     java.lang.System#getProperty(java.lang.String)

      * @see     java.lang.System#getProperty(java.lang.String, java.lang.String)

      */

     public static Integer getInteger(String nm) {

         return getInteger(nm, null);

     }

     /**

      * Determines the integer value of the system property with the

      * specified name.

      *

      * <p>The first argument is treated as the name of a system property.

      * System properties are accessible through the {@link

      * java.lang.System#getProperty(java.lang.String)} method. The

      * string value of this property is then interpreted as an integer

      * value and an {@code Integer} object representing this value is

      * returned. Details of possible numeric formats can be found with

      * the definition of {@code getProperty}.

      *

      * <p>The second argument is the default value. An {@code Integer} object

      * that represents the value of the second argument is returned if there

      * is no property of the specified name, if the property does not have

      * the correct numeric format, or if the specified name is empty or

      * {@code null}.

      *

      * <p>In other words, this method returns an {@code Integer} object

      * equal to the value of:

      *

      * <blockquote>

      *  {@code getInteger(nm, new Integer(val))}

      * </blockquote>

      *

      * but in practice it may be implemented in a manner such as:

      *

      * <blockquote><pre>

      * Integer result = getInteger(nm, null);

      * return (result == null) ? new Integer(val) : result;

      * </pre></blockquote>

      *

      * to avoid the unnecessary allocation of an {@code Integer}

      * object when the default value is not needed.

      *

      * @param   nm   property name.

      * @param   val   default value.

      * @return  the {@code Integer} value of the property.

      * @see     java.lang.System#getProperty(java.lang.String)

      * @see     java.lang.System#getProperty(java.lang.String, java.lang.String)

      */

     public static Integer getInteger(String nm, int val) {

         Integer result = getInteger(nm, null);

         return (result == null) ? Integer.valueOf(val) : result;

     }

     /**

      * Returns the integer value of the system property with the

      * specified name.  The first argument is treated as the name of a

      * system property.  System properties are accessible through the

      * {@link java.lang.System#getProperty(java.lang.String)} method.

      * The string value of this property is then interpreted as an

      * integer value, as per the {@code Integer.decode} method,

      * and an {@code Integer} object representing this value is

      * returned.

      *

      * <ul><li>If the property value begins with the two ASCII characters

      *         {@code 0x} or the ASCII character {@code #}, not

      *      followed by a minus sign, then the rest of it is parsed as a

      *      hexadecimal integer exactly as by the method

      *      {@link #valueOf(java.lang.String, int)} with radix 16.

      * <li>If the property value begins with the ASCII character

      *     {@code 0} followed by another character, it is parsed as an

      *     octal integer exactly as by the method

      *     {@link #valueOf(java.lang.String, int)} with radix 8.

      * <li>Otherwise, the property value is parsed as a decimal integer

      * exactly as by the method {@link #valueOf(java.lang.String, int)}

      * with radix 10.

      * </ul>

      *

      * <p>The second argument is the default value. The default value is

      * returned if there is no property of the specified name, if the

      * property does not have the correct numeric format, or if the

      * specified name is empty or {@code null}.

      *

      * @param   nm   property name.

      * @param   val   default value.

      * @return  the {@code Integer} value of the property.

      * @see     java.lang.System#getProperty(java.lang.String)

      * @see java.lang.System#getProperty(java.lang.String, java.lang.String)

      * @see java.lang.Integer#decode

      */

     public static Integer getInteger(String nm, Integer val) {

         String v = null;

         try {

             v = System.getProperty(nm);

         } catch (IllegalArgumentException e) {

         } catch (NullPointerException e) {

         }

         if (v != null) {

             try {

                 return Integer.decode(v);

             } catch (NumberFormatException e) {

             }

         }

         return val;

     }

     /**

      * Decodes a {@code String} into an {@code Integer}.

      * Accepts decimal, hexadecimal, and octal numbers given

      * by the following grammar:

      *

      * <blockquote>

      * <dl>

      * <dt><i>DecodableString:</i>

      * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i>

      * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i>

      * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i>

      * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i>

      * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i>

      * <p>

      * <dt><i>Sign:</i>

      * <dd>{@code -}

      * <dd>{@code +}

      * </dl>

      * </blockquote>

      *

      * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i>

      * are as defined in section 3.10.1 of

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

      * except that underscores are not accepted between digits.

      *

      * <p>The sequence of characters following an optional

      * sign and/or radix specifier ("{@code 0x}", "{@code 0X}",

      * "{@code #}", or leading zero) is parsed as by the {@code

      * Integer.parseInt} method with the indicated radix (10, 16, or

      * 8).  This sequence of characters must represent a positive

      * value or a {@link NumberFormatException} will be thrown.  The

      * result is negated if first character of the specified {@code

      * String} is the minus sign.  No whitespace characters are

      * permitted in the {@code String}.

      *

      * @param     nm the {@code String} to decode.

      * @return    an {@code Integer} object holding the {@code int}

      *             value represented by {@code nm}

      * @exception NumberFormatException  if the {@code String} does not

      *            contain a parsable integer.

      * @see java.lang.Integer#parseInt(java.lang.String, int)

      */

     public static Integer decode(String nm) throws NumberFormatException {

         int radix = 10;

         int index = 0;

         boolean negative = false;

         Integer result;

         if (nm.length() == 0)

             throw new NumberFormatException("Zero length string");

         char firstChar = nm.charAt(0);

         // Handle sign, if present

         if (firstChar == '-') {

             negative = true;

             index++;

         } else if (firstChar == '+')

             index++;

         // Handle radix specifier, if present

         if (nm.startsWith("0x", index) || nm.startsWith("0X", index)) {

             index += 2;

             radix = 16;

         }

         else if (nm.startsWith("#", index)) {

             index ++;

             radix = 16;

         }

         else if (nm.startsWith("0", index) && nm.length() > 1 + index) {

             index ++;

             radix = 8;

         }

         if (nm.startsWith("-", index) || nm.startsWith("+", index))

             throw new NumberFormatException("Sign character in wrong position");

         try {

             result = Integer.valueOf(nm.substring(index), radix);

             result = negative ? Integer.valueOf(-result.intValue()) : result;

         } catch (NumberFormatException e) {

             // If number is Integer.MIN_VALUE, we'll end up here. The next line

             // handles this case, and causes any genuine format error to be

             // rethrown.

             String constant = negative ? ("-" + nm.substring(index))

                                        : nm.substring(index);

             result = Integer.valueOf(constant, radix);

         }

         return result;

     }

     /**

      * Compares two {@code Integer} objects numerically.

      *

      * @param   anotherInteger   the {@code Integer} to be compared.

      * @return  the value {@code 0} if this {@code Integer} is

      *          equal to the argument {@code Integer}; a value less than

      *          {@code 0} if this {@code Integer} is numerically less

      *          than the argument {@code Integer}; and a value greater

      *          than {@code 0} if this {@code Integer} is numerically

      *           greater than the argument {@code Integer} (signed

      *           comparison).

      * @since   1.2

      */

     public int compareTo(Integer anotherInteger) {

         return compare(this.value, anotherInteger.value);

     }

     /**

      * Compares two {@code int} values numerically.

      * The value returned is identical to what would be returned by:

      * <pre>

      *    Integer.valueOf(x).compareTo(Integer.valueOf(y))

      * </pre>

      *

      * @param  x the first {@code int} to compare

      * @param  y the second {@code int} to compare

      * @return the value {@code 0} if {@code x == y};

      *         a value less than {@code 0} if {@code x < y}; and

      *         a value greater than {@code 0} if {@code x > y}

      * @since 1.7

      */

     public static int compare(int x, int y) {

         return (x < y) ? -1 : ((x == y) ? 0 : 1);

     }

     // Bit twiddling

     /**

      * The number of bits used to represent an {@code int} value in two's

      * complement binary form.

      *

      * @since 1.5

      */

     public static final int SIZE = 32;

     /**

      * Returns an {@code int} value with at most a single one-bit, in the

      * position of the highest-order ("leftmost") one-bit in the specified

      * {@code int} value.  Returns zero if the specified value has no

      * one-bits in its two's complement binary representation, that is, if it

      * is equal to zero.

      *

      * @return an {@code int} value with a single one-bit, in the position

      *     of the highest-order one-bit in the specified value, or zero if

      *     the specified value is itself equal to zero.

      * @since 1.5

      */

     public static int highestOneBit(int i) {

         // HD, Figure 3-1

         i |= (i >>  1);

         i |= (i >>  2);

         i |= (i >>  4);

         i |= (i >>  8);

         i |= (i >> 16);

         return i - (i >>> 1);

     }

     /**

      * Returns an {@code int} value with at most a single one-bit, in the

      * position of the lowest-order ("rightmost") one-bit in the specified

      * {@code int} value.  Returns zero if the specified value has no

      * one-bits in its two's complement binary representation, that is, if it

      * is equal to zero.

      *

      * @return an {@code int} value with a single one-bit, in the position

      *     of the lowest-order one-bit in the specified value, or zero if

      *     the specified value is itself equal to zero.

      * @since 1.5

      */

     public static int lowestOneBit(int i) {

         // HD, Section 2-1

         return i & -i;

     }

     /**

      * Returns the number of zero bits preceding the highest-order

      * ("leftmost") one-bit in the two's complement binary representation

      * of the specified {@code int} value.  Returns 32 if the

      * specified value has no one-bits in its two's complement representation,

      * in other words if it is equal to zero.

      *

      * <p>Note that this method is closely related to the logarithm base 2.

      * For all positive {@code int} values x:

      * <ul>

      * <li>floor(log<sub>2</sub>(x)) = {@code 31 - numberOfLeadingZeros(x)}

      * <li>ceil(log<sub>2</sub>(x)) = {@code 32 - numberOfLeadingZeros(x - 1)}

      * </ul>

      *

      * @return the number of zero bits preceding the highest-order

      *     ("leftmost") one-bit in the two's complement binary representation

      *     of the specified {@code int} value, or 32 if the value

      *     is equal to zero.

      * @since 1.5

      */

     public static int numberOfLeadingZeros(int i) {

         // HD, Figure 5-6

         if (i == 0)

             return 32;

         int n = 1;

         if (i >>> 16 == 0) { n += 16; i <<= 16; }

         if (i >>> 24 == 0) { n +=  8; i <<=  8; }

         if (i >>> 28 == 0) { n +=  4; i <<=  4; }

         if (i >>> 30 == 0) { n +=  2; i <<=  2; }

         n -= i >>> 31;

         return n;

     }

     /**

      * Returns the number of zero bits following the lowest-order ("rightmost")

      * one-bit in the two's complement binary representation of the specified

      * {@code int} value.  Returns 32 if the specified value has no

      * one-bits in its two's complement representation, in other words if it is

      * equal to zero.

      *

      * @return the number of zero bits following the lowest-order ("rightmost")

      *     one-bit in the two's complement binary representation of the

      *     specified {@code int} value, or 32 if the value is equal

      *     to zero.

      * @since 1.5

      */

     public static int numberOfTrailingZeros(int i) {

         // HD, Figure 5-14

         int y;

         if (i == 0) return 32;

         int n = 31;

         y = i <<16; if (y != 0) { n = n -16; i = y; }

         y = i << 8; if (y != 0) { n = n - 8; i = y; }

         y = i << 4; if (y != 0) { n = n - 4; i = y; }

         y = i << 2; if (y != 0) { n = n - 2; i = y; }

         return n - ((i << 1) >>> 31);

     }

     /**

      * Returns the number of one-bits in the two's complement binary

      * representation of the specified {@code int} value.  This function is

      * sometimes referred to as the <i>population count</i>.

      *

      * @return the number of one-bits in the two's complement binary

      *     representation of the specified {@code int} value.

      * @since 1.5

      */

     public static int bitCount(int i) {

         // HD, Figure 5-2

         i = i - ((i >>> 1) & 0x55555555);

         i = (i & 0x33333333) + ((i >>> 2) & 0x33333333);

         i = (i + (i >>> 4)) & 0x0f0f0f0f;

         i = i + (i >>> 8);

         i = i + (i >>> 16);

         return i & 0x3f;

     }

     /**

      * Returns the value obtained by rotating the two's complement binary

      * representation of the specified {@code int} value left by the

      * specified number of bits.  (Bits shifted out of the left hand, or

      * high-order, side reenter on the right, or low-order.)

      *

      * <p>Note that left rotation with a negative distance is equivalent to

      * right rotation: {@code rotateLeft(val, -distance) == rotateRight(val,

      * distance)}.  Note also that rotation by any multiple of 32 is a

      * no-op, so all but the last five bits of the rotation distance can be

      * ignored, even if the distance is negative: {@code rotateLeft(val,

      * distance) == rotateLeft(val, distance & 0x1F)}.

      *

      * @return the value obtained by rotating the two's complement binary

      *     representation of the specified {@code int} value left by the

      *     specified number of bits.

      * @since 1.5

      */

     public static int rotateLeft(int i, int distance) {

         return (i << distance) | (i >>> -distance);

     }

     /**

      * Returns the value obtained by rotating the two's complement binary

      * representation of the specified {@code int} value right by the

      * specified number of bits.  (Bits shifted out of the right hand, or

      * low-order, side reenter on the left, or high-order.)

      *

      * <p>Note that right rotation with a negative distance is equivalent to

      * left rotation: {@code rotateRight(val, -distance) == rotateLeft(val,

      * distance)}.  Note also that rotation by any multiple of 32 is a

      * no-op, so all but the last five bits of the rotation distance can be

      * ignored, even if the distance is negative: {@code rotateRight(val,

      * distance) == rotateRight(val, distance & 0x1F)}.

      *

      * @return the value obtained by rotating the two's complement binary

      *     representation of the specified {@code int} value right by the

      *     specified number of bits.

      * @since 1.5

      */

     public static int rotateRight(int i, int distance) {

         return (i >>> distance) | (i << -distance);

     }

     /**

      * Returns the value obtained by reversing the order of the bits in the

      * two's complement binary representation of the specified {@code int}

      * value.

      *

      * @return the value obtained by reversing order of the bits in the

      *     specified {@code int} value.

      * @since 1.5

      */

     public static int reverse(int i) {

         // HD, Figure 7-1

         i = (i & 0x55555555) << 1 | (i >>> 1) & 0x55555555;

         i = (i & 0x33333333) << 2 | (i >>> 2) & 0x33333333;

         i = (i & 0x0f0f0f0f) << 4 | (i >>> 4) & 0x0f0f0f0f;

         i = (i << 24) | ((i & 0xff00) << 8) |

             ((i >>> 8) & 0xff00) | (i >>> 24);

         return i;

     }

     /**

      * Returns the signum function of the specified {@code int} value.  (The

      * return value is -1 if the specified value is negative; 0 if the

      * specified value is zero; and 1 if the specified value is positive.)

      *

      * @return the signum function of the specified {@code int} value.

      * @since 1.5

      */

     public static int signum(int i) {

         // HD, Section 2-7

         return (i >> 31) | (-i >>> 31);

     }

     /**

      * Returns the value obtained by reversing the order of the bytes in the

      * two's complement representation of the specified {@code int} value.

      *

      * @return the value obtained by reversing the bytes in the specified

      *     {@code int} value.

      * @since 1.5

      */

     public static int reverseBytes(int i) {

         return ((i >>> 24)           ) |

                ((i >>   8) &   0xFF00) |

                ((i <<   8) & 0xFF0000) |

                ((i << 24));

     }

     /** use serialVersionUID from JDK 1.0.2 for interoperability */

     private static final long serialVersionUID = 1360826667806852920L;

 }