https://openjdk.java.net/ 
/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * 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,
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 *
 * 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.misc.CDS;
import jdk.internal.misc.VM;
import jdk.internal.vm.annotation.IntrinsicCandidate;

import static java.lang.String.COMPACT_STRINGS;
import static java.lang.String.LATIN1;
import static java.lang.String.UTF16;


The Integer class wraps a value of the primitive type int in an object. An object of type Integer contains a single field whose type is int. 
In addition, this class provides several methods for converting an int to a String and a String to an int, as well as other constants and methods useful when dealing with an int. 
This is a value-based class; programmers should treat instances that are equal as interchangeable and should not use instances for synchronization, or unpredictable behavior may occur. For example, in a future release, synchronization may fail. 
Implementation note: The implementations of the "bit twiddling" methods (such as highestOneBit and numberOfTrailingZeros) are based on material from Henry S. Warren, Jr.'s Hacker's
Delight, (Addison Wesley, 2002).

Author: Lee Boynton,  Arthur van Hoff,  Josh Bloch,  Joseph D. Darcy
Since:1.0
/**
 * 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>This is a <a href="{@docRoot}/java.base/java/lang/doc-files/ValueBased.html">value-based</a>
 * class; programmers should treat instances that are
 * {@linkplain #equals(Object) equal} as interchangeable and should not
 * use instances for synchronization, or unpredictable behavior may
 * occur. For example, in a future release, synchronization may fail.
 *
 * <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
 */
@jdk.internal.ValueBased
public final class Integer extends Number
        implements Comparable<Integer>, Constable, ConstantDesc {
    
A constant holding the minimum value an int can have, -231.

/**
     * 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 int can have, 231-1.

/**
     * 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 Class instance representing the primitive type int. 
Since:  1.1
/**
     * 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

/**
     * 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.

If the radix is smaller than Character.MIN_RADIX or larger than Character.MAX_RADIX, then the radix 10 is used instead. 
If the first argument is negative, the first element of the result is the ASCII minus character '-' ('\u005Cu002D'). If the first argument is not negative, no sign character appears in the result. 
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 '0' ('\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: 
 0123456789abcdefghijklmnopqrstuvwxyz 
 These are '\u005Cu0030' through '\u005Cu0039' and '\u005Cu0061' through '\u005Cu007A'. If radix is N, then the first N of these characters
are used as radix-N digits in the order shown. Thus, the digits for hexadecimal (radix 16) are 0123456789abcdef. If uppercase letters are desired, the String.toUpperCase() method may be called on the result: 
 Integer.toString(n, 16).toUpperCase() 


Params:
  • i –       an integer to be converted to a string.
  • radix –   the radix to use in the string representation.
See Also:
Returns: a string representation of the argument in the specified radix.
/**
     * 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.

If the radix is smaller than Character.MIN_RADIX or larger than Character.MAX_RADIX, then the radix 10 is used instead. 
Note that since the first argument is treated as an unsigned
value, no leading sign character is printed.

If the magnitude is zero, it is represented by a single zero character '0' ('\u005Cu0030'); otherwise, the first character of the representation of the magnitude will not be the zero character. 
The behavior of radixes and the characters used as digits are the same as toString. 
Params:
  • i –       an integer to be converted to an unsigned string.
  • radix –   the radix to use in the string representation.
See Also:
Returns: an unsigned string representation of the argument in the specified radix.
Since:1.8
/**
     * 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.

The unsigned integer value is the argument plus 232 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 0s. 
The value of the argument can be recovered from the returned string s by calling 
Integer.parseUnsignedInt(s, 16). 
If the unsigned magnitude is zero, it is represented by a single zero character '0' ('\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: 
 0123456789abcdef 
 These are the characters '\u005Cu0030' through '\u005Cu0039' and '\u005Cu0061' through '\u005Cu0066'. If uppercase letters are desired, the String.toUpperCase() method may be called on the result: 
 Integer.toHexString(n).toUpperCase() 


Params:
  • i –   an integer to be converted to a string.
See Also:
API Note: The HexFormat class provides formatting and parsing of byte arrays and primitives to return a string or adding to an Appendable. HexFormat formats and parses uppercase or lowercase hexadecimal characters, with leading zeros and for byte arrays includes for each byte a delimiter, prefix, and suffix.
Returns: the string representation of the unsigned integer value
         represented by the argument in hexadecimal (base 16).
Since:  1.0.2
/**
     * Returns a string representation of the integer argument as an
     * unsigned integer in base&nbsp;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&nbsp;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>
     *
     * @apiNote
     * The {@link java.util.HexFormat} class provides formatting and parsing
     * of byte arrays and primitives to return a string or adding to an {@link Appendable}.
     * {@code HexFormat} formats and parses uppercase or lowercase hexadecimal characters,
     * with leading zeros and for byte arrays includes for each byte
     * a delimiter, prefix, and suffix.
     *
     * @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&nbsp;16).
     * @see java.util.HexFormat
     * @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.

The unsigned integer value is the argument plus 232 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 0s. 
The value of the argument can be recovered from the returned string s by calling 
Integer.parseUnsignedInt(s, 8). 
If the unsigned magnitude is zero, it is represented by a single zero character '0' ('\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: 
 01234567 
 These are the characters '\u005Cu0030' through '\u005Cu0037'. 
Params:
  • i –   an integer to be converted to a string.
See Also:
Returns: the string representation of the unsigned integer value
         represented by the argument in octal (base 8).
Since:  1.0.2
/**
     * Returns a string representation of the integer argument as an
     * unsigned integer in base&nbsp;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&nbsp;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&nbsp;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.

The unsigned integer value is the argument plus 232 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 0s. 
The value of the argument can be recovered from the returned string s by calling 
Integer.parseUnsignedInt(s, 2). 
If the unsigned magnitude is zero, it is represented by a single zero character '0' ('\u005Cu0030'); otherwise, the first character of the representation of the unsigned magnitude will not be the zero character. The characters '0' ('\u005Cu0030') and 
'1' ('\u005Cu0031') are used as binary digits. 
Params:
  • i –   an integer to be converted to a string.
See Also:
Returns: the string representation of the unsigned integer value
         represented by the argument in binary (base 2).
Since:  1.0.2
/**
     * Returns a string representation of the integer argument as an
     * unsigned integer in base&nbsp;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&nbsp;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&nbsp;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.

/**
     * 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 int (treated as unsigned) into a byte buffer (LATIN1 version). If len exceeds the formatted ASCII representation of val, buf will be padded with leading zeroes. 
Params:
  • val – the unsigned int to format
  • shift – the log2 of the base to format in (4 for hex, 3 for octal, 1 for binary)
  • buf – the byte buffer to write to
  • len – the number of characters to write
/**
     * 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 int (treated as unsigned) into a byte buffer (UTF16 version). If len exceeds the formatted ASCII representation of val, buf will be padded with leading zeroes. 
Params:
  • val – the unsigned int to format
  • shift – the log2 of the base to format in (4 for hex, 3 for octal, 1 for binary)
  • buf – the byte buffer to write to
  • len – the number of characters to write
/**
     * 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 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 toString(int, int) method. 
Params:
  • i –   an integer to be converted.
Returns: a string representation of the argument in base 10.
/**
     * 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&nbsp;10.
     */
    @IntrinsicCandidate
    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 toUnsignedString(int, int) method. 
Params:
  • i –  an integer to be converted to an unsigned string.
See Also:
Returns: an unsigned string representation of the argument.
Since:1.8
/**
     * 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.

Params:
  • i –     value to convert
  • index – next index, after the least significant digit
  • buf –   target buffer, Latin1-encoded
Implementation Note: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.
Returns:index of the most significant digit or minus sign, if present
/**
     * 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.
        q = i / 10;
        r = (q * 10) - i;
        buf[--charPos] = (byte)('0' + r);

        // Whatever left is the remaining digit.
        if (q < 0) {
            buf[--charPos] = (byte)('0' - q);
        }

        if (negative) {
            buf[--charPos] = (byte)'-';
        }
        return charPos;
    }

    // Left here for compatibility reasons, see JDK-8143900.
    static final int [] sizeTable = { 9, 99, 999, 9999, 99999, 999999, 9999999,
                                      99999999, 999999999, Integer.MAX_VALUE };

    
Returns the string representation size for a given int value.

Params:
  • x – int value
Returns:string size
Implementation Note:There are other ways to compute this: e.g. binary search,
but values are biased heavily towards zero, and therefore linear search
wins. The iteration results are also routinely inlined in the generated
code after loop unrolling.
/**
     * Returns the string representation size for a given int value.
     *
     * @param x int value
     * @return string size
     *
     * @implNote There are other ways to compute this: e.g. binary search,
     * but values are biased heavily towards zero, and therefore linear search
     * wins. The iteration results are also routinely inlined in the generated
     * code after loop unrolling.
     */
    static int stringSize(int x) {
        int d = 1;
        if (x >= 0) {
            d = 0;
            x = -x;
        }
        int p = -10;
        for (int i = 1; i < 10; i++) {
            if (x > p)
                return i + d;
            p = 10 * p;
        }
        return 10 + d;
    }

    
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 Character.digit(char, int) returns a nonnegative value), except that the first character may be an ASCII minus sign '-' ('\u005Cu002D') to indicate a negative value or an ASCII plus sign '+' ('\u005Cu002B') to indicate a positive value. The resulting integer value is returned. 
An exception of type NumberFormatException is thrown if any of the following situations occurs: 
    

  • The first argument is null or is a string of length zero. 
  • The radix is either smaller than Character.MIN_RADIX or larger than Character.MAX_RADIX. 
  • Any character of the string is not a digit of the specified radix, except that the first character may be a minus sign '-' ('\u005Cu002D') or plus sign '+' ('\u005Cu002B') provided that the string is longer than length 1. 
  • The value represented by the string is not a value of type int. 


Examples:

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



Params:
  • s –  the String containing the integer representation to be parsed
  • radix –  the radix to be used while parsing s.
Throws:
Returns:    the integer represented by the string argument in the
            specified radix.
/**
     * 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 '\u005Cu002D'}) to
     * indicate a negative value or an ASCII plus sign {@code '+'}
     * ({@code '\u005Cu002B'}) 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 '\u005Cu002D'}) or plus sign
     * {@code '+'} ({@code '\u005Cu002B'}) 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.
     * @throws     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("Cannot parse null string");
        }

        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");
        }

        boolean negative = false;
        int i = 0, len = s.length();
        int limit = -Integer.MAX_VALUE;

        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, radix);
                }

                if (len == 1) { // Cannot have lone "+" or "-"
                    throw NumberFormatException.forInputString(s, radix);
                }
                i++;
            }
            int multmin = limit / radix;
            int result = 0;
            while (i < len) {
                // Accumulating negatively avoids surprises near MAX_VALUE
                int digit = Character.digit(s.charAt(i++), radix);
                if (digit < 0 || result < multmin) {
                    throw NumberFormatException.forInputString(s, radix);
                }
                result *= radix;
                if (result < limit + digit) {
                    throw NumberFormatException.forInputString(s, radix);
                }
                result -= digit;
            }
            return negative ? result : -result;
        } else {
            throw NumberFormatException.forInputString(s, radix);
        }
    }

    
Parses the CharSequence argument as a signed int in the specified radix, beginning at the specified beginIndex and extending to endIndex - 1. 
The method does not take steps to guard against the CharSequence being mutated while parsing. 
Params:
  • s –  the CharSequence containing the int representation to be parsed
  • beginIndex –   the beginning index, inclusive.
  • endIndex –     the ending index, exclusive.
  • radix –  the radix to be used while parsing s.
Throws:
Returns: the signed int represented by the subsequence in the specified radix.
Since: 9
/**
     * Parses the {@link CharSequence} argument as a signed {@code int} in the
     * specified {@code radix}, beginning at the specified {@code beginIndex}
     * and extending to {@code endIndex - 1}.
     *
     * <p>The method does not take steps to guard against the
     * {@code CharSequence} being mutated while parsing.
     *
     * @param      s   the {@code CharSequence} containing the {@code int}
     *                  representation to be parsed
     * @param      beginIndex   the beginning index, inclusive.
     * @param      endIndex     the ending index, exclusive.
     * @param      radix   the radix to be used while parsing {@code s}.
     * @return     the signed {@code int} represented by the subsequence in
     *             the specified radix.
     * @throws     NullPointerException  if {@code s} is null.
     * @throws     IndexOutOfBoundsException  if {@code beginIndex} is
     *             negative, or if {@code beginIndex} is greater than
     *             {@code endIndex} or if {@code endIndex} is greater than
     *             {@code s.length()}.
     * @throws     NumberFormatException  if the {@code CharSequence} does not
     *             contain a parsable {@code int} in the specified
     *             {@code radix}, or if {@code radix} is either smaller than
     *             {@link java.lang.Character#MIN_RADIX} or larger than
     *             {@link java.lang.Character#MAX_RADIX}.
     * @since  9
     */
    public static int parseInt(CharSequence s, int beginIndex, int endIndex, int radix)
                throws NumberFormatException {
        Objects.requireNonNull(s);

        if (beginIndex < 0 || beginIndex > endIndex || endIndex > s.length()) {
            throw new IndexOutOfBoundsException();
        }
        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");
        }

        boolean negative = false;
        int i = beginIndex;
        int limit = -Integer.MAX_VALUE;

        if (i < endIndex) {
            char firstChar = s.charAt(i);
            if (firstChar < '0') { // Possible leading "+" or "-"
                if (firstChar == '-') {
                    negative = true;
                    limit = Integer.MIN_VALUE;
                } else if (firstChar != '+') {
                    throw NumberFormatException.forCharSequence(s, beginIndex,
                            endIndex, i);
                }
                i++;
                if (i == endIndex) { // Cannot have lone "+" or "-"
                    throw NumberFormatException.forCharSequence(s, beginIndex,
                            endIndex, i);
                }
            }
            int multmin = limit / radix;
            int result = 0;
            while (i < endIndex) {
                // Accumulating negatively avoids surprises near MAX_VALUE
                int digit = Character.digit(s.charAt(i), radix);
                if (digit < 0 || result < multmin) {
                    throw NumberFormatException.forCharSequence(s, beginIndex,
                            endIndex, i);
                }
                result *= radix;
                if (result < limit + digit) {
                    throw NumberFormatException.forCharSequence(s, beginIndex,
                            endIndex, i);
                }
                i++;
                result -= digit;
            }
            return negative ? result : -result;
        } else {
            throw NumberFormatException.forInputString("", radix);
        }
    }

    
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 '-' ('\u005Cu002D') to indicate a negative value or an ASCII plus sign '+' ('\u005Cu002B') 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 parseInt(String, int) method. 
Params:
  • s –  a String containing the int representation to be parsed
Throws:
Returns:    the integer value represented by the argument in decimal.
/**
     * 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 '\u005Cu002D'}) to indicate a negative value or an
     * ASCII plus sign {@code '+'} ({@code '\u005Cu002B'}) 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.
     * @throws     NumberFormatException  if the string does not contain a
     *               parsable integer.
     */
    public static int parseInt(String s) throws NumberFormatException {
        return parseInt(s,10);
    }

    
Parses the string argument as an unsigned integer in the radix specified by the second argument. An unsigned integer maps the values usually associated with negative numbers to positive numbers larger than MAX_VALUE. The characters in the string must all be digits of the specified radix (as determined by whether Character.digit(char, int) returns a nonnegative value), except that the first character may be an ASCII plus sign '+' ('\u005Cu002B'). The resulting integer value is returned. 
An exception of type NumberFormatException is thrown if any of the following situations occurs: 
    

  • The first argument is null or is a string of length zero. 
  • The radix is either smaller than Character.MIN_RADIX or larger than Character.MAX_RADIX. 
  • Any character of the string is not a digit of the specified radix, except that the first character may be a plus sign '+' ('\u005Cu002B') provided that the string is longer than length 1. 
  • The value represented by the string is larger than the largest unsigned int, 232-1.



Params:
  • s –  the String containing the unsigned integer representation to be parsed
  • radix –  the radix to be used while parsing s.
Throws:
Returns:    the integer represented by the string argument in the
            specified radix.
Since:1.8
/**
     * Parses the string argument as an unsigned integer in the radix
     * specified by the second argument.  An unsigned integer maps the
     * values usually associated with negative numbers to positive
     * numbers larger than {@code MAX_VALUE}.
     *
     * 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 plus
     * sign {@code '+'} ({@code '\u005Cu002B'}). 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 plus sign
     * {@code '+'} ({@code '\u005Cu002B'}) provided that the
     * string is longer than length 1.
     *
     * <li>The value represented by the string is larger than the
     * largest unsigned {@code int}, 2<sup>32</sup>-1.
     *
     * </ul>
     *
     *
     * @param      s   the {@code String} containing the unsigned 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.
     * @throws     NumberFormatException if the {@code String}
     *             does not contain a parsable {@code int}.
     * @since 1.8
     */
    public static int parseUnsignedInt(String s, int radix)
                throws NumberFormatException {
        if (s == null)  {
            throw new NumberFormatException("Cannot parse null string");
        }

        int len = s.length();
        if (len > 0) {
            char firstChar = s.charAt(0);
            if (firstChar == '-') {
                throw new
                    NumberFormatException(String.format("Illegal leading minus sign " +
                                                       "on unsigned string %s.", s));
            } else {
                if (len <= 5 || // Integer.MAX_VALUE in Character.MAX_RADIX is 6 digits
                    (radix == 10 && len <= 9) ) { // Integer.MAX_VALUE in base 10 is 10 digits
                    return parseInt(s, radix);
                } else {
                    long ell = Long.parseLong(s, radix);
                    if ((ell & 0xffff_ffff_0000_0000L) == 0) {
                        return (int) ell;
                    } else {
                        throw new
                            NumberFormatException(String.format("String value %s exceeds " +
                                                                "range of unsigned int.", s));
                    }
                }
            }
        } else {
            throw NumberFormatException.forInputString(s, radix);
        }
    }

    
Parses the CharSequence argument as an unsigned int in the specified radix, beginning at the specified beginIndex and extending to endIndex - 1. 
The method does not take steps to guard against the CharSequence being mutated while parsing. 
Params:
  • s –  the CharSequence containing the unsigned int representation to be parsed
  • beginIndex –   the beginning index, inclusive.
  • endIndex –     the ending index, exclusive.
  • radix –  the radix to be used while parsing s.
Throws:
Returns: the unsigned int represented by the subsequence in the specified radix.
Since: 9
/**
     * Parses the {@link CharSequence} argument as an unsigned {@code int} in
     * the specified {@code radix}, beginning at the specified
     * {@code beginIndex} and extending to {@code endIndex - 1}.
     *
     * <p>The method does not take steps to guard against the
     * {@code CharSequence} being mutated while parsing.
     *
     * @param      s   the {@code CharSequence} containing the unsigned
     *                 {@code int} representation to be parsed
     * @param      beginIndex   the beginning index, inclusive.
     * @param      endIndex     the ending index, exclusive.
     * @param      radix   the radix to be used while parsing {@code s}.
     * @return     the unsigned {@code int} represented by the subsequence in
     *             the specified radix.
     * @throws     NullPointerException  if {@code s} is null.
     * @throws     IndexOutOfBoundsException  if {@code beginIndex} is
     *             negative, or if {@code beginIndex} is greater than
     *             {@code endIndex} or if {@code endIndex} is greater than
     *             {@code s.length()}.
     * @throws     NumberFormatException  if the {@code CharSequence} does not
     *             contain a parsable unsigned {@code int} in the specified
     *             {@code radix}, or if {@code radix} is either smaller than
     *             {@link java.lang.Character#MIN_RADIX} or larger than
     *             {@link java.lang.Character#MAX_RADIX}.
     * @since  9
     */
    public static int parseUnsignedInt(CharSequence s, int beginIndex, int endIndex, int radix)
                throws NumberFormatException {
        Objects.requireNonNull(s);

        if (beginIndex < 0 || beginIndex > endIndex || endIndex > s.length()) {
            throw new IndexOutOfBoundsException();
        }
        int start = beginIndex, len = endIndex - beginIndex;

        if (len > 0) {
            char firstChar = s.charAt(start);
            if (firstChar == '-') {
                throw new
                    NumberFormatException(String.format("Illegal leading minus sign " +
                                                       "on unsigned string %s.", s));
            } else {
                if (len <= 5 || // Integer.MAX_VALUE in Character.MAX_RADIX is 6 digits
                        (radix == 10 && len <= 9)) { // Integer.MAX_VALUE in base 10 is 10 digits
                    return parseInt(s, start, start + len, radix);
                } else {
                    long ell = Long.parseLong(s, start, start + len, radix);
                    if ((ell & 0xffff_ffff_0000_0000L) == 0) {
                        return (int) ell;
                    } else {
                        throw new
                            NumberFormatException(String.format("String value %s exceeds " +
                                                                "range of unsigned int.", s));
                    }
                }
            }
        } else {
            throw new NumberFormatException("");
        }
    }

    
Parses the string argument as an unsigned decimal integer. The characters in the string must all be decimal digits, except that the first character may be an ASCII plus sign 
'+' ('\u005Cu002B'). The resulting integer value is returned, exactly as if the argument and the radix 10 were given as arguments to the parseUnsignedInt(String, int) method. 
Params:
  • s –  a String containing the unsigned int representation to be parsed
Throws:
Returns:   the unsigned integer value represented by the argument in decimal.
Since:1.8
/**
     * Parses the string argument as an unsigned decimal integer. The
     * characters in the string must all be decimal digits, except
     * that the first character may be an ASCII plus sign {@code
     * '+'} ({@code '\u005Cu002B'}). The resulting integer value
     * is returned, exactly as if the argument and the radix 10 were
     * given as arguments to the {@link
     * #parseUnsignedInt(java.lang.String, int)} method.
     *
     * @param s   a {@code String} containing the unsigned {@code int}
     *            representation to be parsed
     * @return    the unsigned integer value represented by the argument in decimal.
     * @throws    NumberFormatException  if the string does not contain a
     *            parsable unsigned integer.
     * @since 1.8
     */
    public static int parseUnsignedInt(String s) throws NumberFormatException {
        return parseUnsignedInt(s, 10);
    }

    
Returns an Integer object holding the value extracted from the specified 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 parseInt(String, int) method. The result is an Integer object that represents the integer value specified by the string. 
In other words, this method returns an Integer object equal to the value of: 
 new Integer(Integer.parseInt(s, radix)) 


Params:
  • s –   the string to be parsed.
  • radix – the radix to be used in interpreting s
Throws:
Returns: an Integer object holding the value represented by the string argument in the specified radix.
/**
     * 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.
     * @throws    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 Integer object holding the value of the specified String. The argument is interpreted as representing a signed decimal integer, exactly as if the argument were given to the parseInt(String) method. The result is an Integer object that represents the integer value specified by the string. 
In other words, this method returns an Integer object equal to the value of: 
 new Integer(Integer.parseInt(s)) 


Params:
  • s –   the string to be parsed.
Throws:
Returns: an Integer object holding the value represented by the string argument.
/**
     * 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.
     * @throws     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 jdk.internal.misc.VM class. WARNING: The cache is archived with CDS and reloaded from the shared archive at runtime. The archived cache (Integer[]) and Integer objects reside in the closed archive heap regions. Care should be taken when changing the implementation and the cache array should not be assigned with new Integer object(s) after initialization. 
/**
     * 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 {@code -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
     * jdk.internal.misc.VM class.
     *
     * WARNING: The cache is archived with CDS and reloaded from the shared
     * archive at runtime. The archived cache (Integer[]) and Integer objects
     * reside in the closed archive heap regions. Care should be taken when
     * changing the implementation and the cache array should not be assigned
     * with new Integer object(s) after initialization.
     */

    private static class IntegerCache {
        static final int low = -128;
        static final int high;
        static final Integer[] cache;
        static Integer[] archivedCache;

        static {
            // high value may be configured by property
            int h = 127;
            String integerCacheHighPropValue =
                VM.getSavedProperty("java.lang.Integer.IntegerCache.high");
            if (integerCacheHighPropValue != null) {
                try {
                    h = Math.max(parseInt(integerCacheHighPropValue), 127);
                    // Maximum array size is Integer.MAX_VALUE
                    h = Math.min(h, Integer.MAX_VALUE - (-low) -1);
                } catch( NumberFormatException nfe) {
                    // If the property cannot be parsed into an int, ignore it.
                }
            }
            high = h;

            // Load IntegerCache.archivedCache from archive, if possible
            CDS.initializeFromArchive(IntegerCache.class);
            int size = (high - low) + 1;

            // Use the archived cache if it exists and is large enough
            if (archivedCache == null || size > archivedCache.length) {
                Integer[] c = new Integer[size];
                int j = low;
                for(int i = 0; i < c.length; i++) {
                    c[i] = new Integer(j++);
                }
                archivedCache = c;
            }
            cache = archivedCache;
            // range [-128, 127] must be interned (JLS7 5.1.7)
            assert IntegerCache.high >= 127;
        }

        private IntegerCache() {}
    }

    
Returns an Integer instance representing the specified int value. If a new Integer instance is not required, this method should generally be used in preference to the constructor 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. 
Params:
  • i – an int value.
Returns:an Integer instance representing i.
Since: 1.5
/**
     * 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
     */
    @IntrinsicCandidate
    public static Integer valueOf(int i) {
        if (i >= IntegerCache.low && i <= IntegerCache.high)
            return IntegerCache.cache[i + (-IntegerCache.low)];
        return new Integer(i);
    }

    
The value of the Integer. 
@serial
/**
     * The value of the {@code Integer}.
     *
     * @serial
     */
    private final int value;

    
Constructs a newly allocated Integer object that represents the specified int value. 
Params:
  • value –  the value to be represented by the Integer object.
Deprecated: It is rarely appropriate to use this constructor. The static factory valueOf(int) is generally a better choice, as it is likely to yield significantly better space and time performance.
/**
     * 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.
     *
     * @deprecated
     * It is rarely appropriate to use this constructor. The static factory
     * {@link #valueOf(int)} is generally a better choice, as it is
     * likely to yield significantly better space and time performance.
     */
    @Deprecated(since="9", forRemoval = true)
    public Integer(int value) {
        this.value = value;
    }

    
Constructs a newly allocated Integer object that represents the int value indicated by the String parameter. The string is converted to an int value in exactly the manner used by the parseInt method for radix 10. 
Params:
  • s –  the String to be converted to an Integer.
Throws:
Deprecated: It is rarely appropriate to use this constructor. Use parseInt(String) to convert a string to a int primitive, or use valueOf(String) to convert a string to an Integer object.
/**
     * 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}.
     * @throws      NumberFormatException if the {@code String} does not
     *              contain a parsable integer.
     *
     * @deprecated
     * It is rarely appropriate to use this constructor.
     * Use {@link #parseInt(String)} to convert a string to a
     * {@code int} primitive, or use {@link #valueOf(String)}
     * to convert a string to an {@code Integer} object.
     */
    @Deprecated(since="9", forRemoval = true)
    public Integer(String s) throws NumberFormatException {
        this.value = parseInt(s, 10);
    }

    
Returns the value of this Integer as a byte after a narrowing primitive conversion. 
@jls5.1.3 Narrowing Primitive Conversion
/**
     * Returns the value of this {@code Integer} as a {@code byte}
     * after a narrowing primitive conversion.
     * @jls 5.1.3 Narrowing Primitive Conversion
     */
    public byte byteValue() {
        return (byte)value;
    }

    
Returns the value of this Integer as a short after a narrowing primitive conversion. 
@jls5.1.3 Narrowing Primitive Conversion
/**
     * Returns the value of this {@code Integer} as a {@code short}
     * after a narrowing primitive conversion.
     * @jls 5.1.3 Narrowing Primitive Conversion
     */
    public short shortValue() {
        return (short)value;
    }

    
Returns the value of this Integer as an int. 
/**
     * Returns the value of this {@code Integer} as an
     * {@code int}.
     */
    @IntrinsicCandidate
    public int intValue() {
        return value;
    }

    
Returns the value of this Integer as a long after a widening primitive conversion. 
See Also:
@jls5.1.2 Widening Primitive Conversion
/**
     * Returns the value of this {@code Integer} as a {@code long}
     * after a widening primitive conversion.
     * @jls 5.1.2 Widening Primitive Conversion
     * @see Integer#toUnsignedLong(int)
     */
    public long longValue() {
        return (long)value;
    }

    
Returns the value of this Integer as a float after a widening primitive conversion. 
@jls5.1.2 Widening Primitive Conversion
/**
     * Returns the value of this {@code Integer} as a {@code float}
     * after a widening primitive conversion.
     * @jls 5.1.2 Widening Primitive Conversion
     */
    public float floatValue() {
        return (float)value;
    }

    
Returns the value of this Integer as a double after a widening primitive conversion. 
@jls5.1.2 Widening Primitive Conversion
/**
     * Returns the value of this {@code Integer} as a {@code double}
     * after a widening primitive conversion.
     * @jls 5.1.2 Widening Primitive Conversion
     */
    public double doubleValue() {
        return (double)value;
    }

    
Returns a String object representing this 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 toString(int) method. 
Returns: a string representation of the value of this object in
         base 10.
/**
     * 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&nbsp;10.
     */
    public String toString() {
        return toString(value);
    }

    
Returns a hash code for this Integer. 
Returns: a hash code value for this object, equal to the primitive int value represented by this Integer object.
/**
     * 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.
     */
    @Override
    public int hashCode() {
        return Integer.hashCode(value);
    }

    
Returns a hash code for an int value; compatible with Integer.hashCode(). 
Params:
  • value – the value to hash
Since:1.8
Returns:a hash code value for an int value.
/**
     * Returns a hash code for an {@code int} value; compatible with
     * {@code Integer.hashCode()}.
     *
     * @param value the value to hash
     * @since 1.8
     *
     * @return a hash code value for an {@code int} value.
     */
    public static int hashCode(int value) {
        return value;
    }

    
Compares this object to the specified object. The result is true if and only if the argument is not null and is an Integer object that contains the same int value as this object. 
Params:
  • obj –   the object to compare with.
Returns: true if the objects are the same; false otherwise.
/**
     * 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.

The first argument is treated as the name of a system property. System properties are accessible through the System.getProperty(String) method. The string value of this property is then interpreted as an integer value using the grammar supported by decode and an Integer object representing this value is returned. 
If there is no property with the specified name, if the specified name is empty or null, or if the property does not have the correct numeric format, then null is returned. 
In other words, this method returns an Integer object equal to the value of: 
 getInteger(nm, null) 


Params:
  • nm –   property name.
Throws:
See Also:
Returns: the Integer value of the property.
/**
     * 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 using the grammar supported by {@link Integer#decode decode} and
     * an {@code Integer} object representing this value is returned.
     *
     * <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.
     * @throws  SecurityException for the same reasons as
     *          {@link System#getProperty(String) System.getProperty}
     * @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.

The first argument is treated as the name of a system property. System properties are accessible through the System.getProperty(String) method. The string value of this property is then interpreted as an integer value using the grammar supported by decode and an Integer object representing this value is returned. 
The second argument is the default value. An 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 null. 
In other words, this method returns an Integer object equal to the value of: 
 getInteger(nm, new Integer(val)) 

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

Integer result = getInteger(nm, null);
return (result == null) ? new Integer(val) : result;

 to avoid the unnecessary allocation of an Integer object when the default value is not needed. 
Params:
  • nm –   property name.
  • val –   default value.
Throws:
See Also:
Returns: the Integer value of the property.
/**
     * 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 using the grammar supported by {@link Integer#decode decode} and
     * an {@code Integer} object representing this value is returned.
     *
     * <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.
     * @throws  SecurityException for the same reasons as
     *          {@link System#getProperty(String) System.getProperty}
     * @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 System.getProperty(String) method. The string value of this property is then interpreted as an integer value, as per the decode method, and an Integer object representing this value is returned; in summary: 
  • If the property value begins with the two ASCII characters 0x or the ASCII character #, not followed by a minus sign, then the rest of it is parsed as a hexadecimal integer exactly as by the method valueOf(String, int) with radix 16. 
  • If the property value begins with the ASCII character 0 followed by another character, it is parsed as an octal integer exactly as by the method valueOf(String, int) with radix 8. 
  • Otherwise, the property value is parsed as a decimal integer exactly as by the method valueOf(String, int) with radix 10. 


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 null. 
Params:
  • nm –   property name.
  • val –   default value.
Throws:
See Also:
Returns: the Integer value of the property.
/**
     * 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 {@link Integer#decode decode} method,
     * and an {@code Integer} object representing this value is
     * returned; in summary:
     *
     * <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.
     * @throws  SecurityException for the same reasons as
     *          {@link System#getProperty(String) System.getProperty}
     * @see     System#getProperty(java.lang.String)
     * @see     System#getProperty(java.lang.String, java.lang.String)
     */
    public static Integer getInteger(String nm, Integer val) {
        String v = null;
        try {
            v = System.getProperty(nm);
        } catch (IllegalArgumentException | NullPointerException e) {
        }
        if (v != null) {
            try {
                return Integer.decode(v);
            } catch (NumberFormatException e) {
            }
        }
        return val;
    }

    
Decodes a String into an Integer. Accepts decimal, hexadecimal, and octal numbers given by the following grammar: 




DecodableString:

Signopt DecimalNumeral

Signopt 0x HexDigits

Signopt 0X HexDigits

Signopt # HexDigits

Signopt 0 OctalDigits

Sign:

- 
+ 



DecimalNumeral, HexDigits, and OctalDigits
are as defined in section {@jls 3.10.1} of
The Java Language Specification,
except that underscores are not accepted between digits.

The sequence of characters following an optional sign and/or radix specifier ("0x", "0X", "#", or leading zero) is parsed as by the 
Integer.parseInt method with the indicated radix (10, 16, or 8). This sequence of characters must represent a positive value or a NumberFormatException will be thrown. The result is negated if first character of the specified 
String is the minus sign. No whitespace characters are permitted in the String. 
Params:
  • nm – the String to decode.
Throws:
See Also:
Returns: an Integer object holding the int value represented by nm
/**
     * 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>
     *
     * <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 {@jls 3.10.1} of
     * <cite>The Java 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}
     * @throws    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.isEmpty())
            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 Integer objects numerically. 
Params:
  • anotherInteger –  the Integer to be compared.
Returns: the value 0 if this Integer is equal to the argument Integer; a value less than 0 if this Integer is numerically less than the argument Integer; and a value greater than 0 if this Integer is numerically greater than the argument Integer (signed comparison).
Since:  1.2
/**
     * 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 int values numerically. The value returned is identical to what would be returned by: 
   Integer.valueOf(x).compareTo(Integer.valueOf(y))



Params:
  • x – the first int to compare
  • y – the second int to compare
Returns:the value 0 if x == y; a value less than 0 if x < y; and a value greater than 0 if x > y
Since:1.7
/**
     * 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);
    }

    
Compares two int values numerically treating the values as unsigned. 
Params:
  • x – the first int to compare
  • y – the second int to compare
Returns:the value 0 if x == y; a value less than 0 if x < y as unsigned values; and a value greater than 0 if x > y as unsigned values
Since:1.8
/**
     * Compares two {@code int} values numerically treating the values
     * as unsigned.
     *
     * @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} as unsigned values; and
     *         a value greater than {@code 0} if {@code x > y} as
     *         unsigned values
     * @since 1.8
     */
    public static int compareUnsigned(int x, int y) {
        return compare(x + MIN_VALUE, y + MIN_VALUE);
    }

    
Converts the argument to a long by an unsigned conversion. In an unsigned conversion to a long, the high-order 32 bits of the long are zero and the low-order 32 bits are equal to the bits of the integer argument. Consequently, zero and positive int values are mapped to a numerically equal long value and negative 
int values are mapped to a long value equal to the input plus 232.

Params:
  • x – the value to convert to an unsigned long
Returns:the argument converted to long by an unsigned conversion
Since:1.8
/**
     * Converts the argument to a {@code long} by an unsigned
     * conversion.  In an unsigned conversion to a {@code long}, the
     * high-order 32 bits of the {@code long} are zero and the
     * low-order 32 bits are equal to the bits of the integer
     * argument.
     *
     * Consequently, zero and positive {@code int} values are mapped
     * to a numerically equal {@code long} value and negative {@code
     * int} values are mapped to a {@code long} value equal to the
     * input plus 2<sup>32</sup>.
     *
     * @param  x the value to convert to an unsigned {@code long}
     * @return the argument converted to {@code long} by an unsigned
     *         conversion
     * @since 1.8
     */
    public static long toUnsignedLong(int x) {
        return ((long) x) & 0xffffffffL;
    }

    
Returns the unsigned quotient of dividing the first argument by
the second where each argument and the result is interpreted as
an unsigned value.

Note that in two's complement arithmetic, the three other basic arithmetic operations of add, subtract, and multiply are bit-wise identical if the two operands are regarded as both being signed or both being unsigned. Therefore separate 
addUnsigned, etc. methods are not provided. 
Params:
  • dividend – the value to be divided
  • divisor – the value doing the dividing
See Also:
Returns:the unsigned quotient of the first argument divided by
the second argument
Since:1.8
/**
     * Returns the unsigned quotient of dividing the first argument by
     * the second where each argument and the result is interpreted as
     * an unsigned value.
     *
     * <p>Note that in two's complement arithmetic, the three other
     * basic arithmetic operations of add, subtract, and multiply are
     * bit-wise identical if the two operands are regarded as both
     * being signed or both being unsigned.  Therefore separate {@code
     * addUnsigned}, etc. methods are not provided.
     *
     * @param dividend the value to be divided
     * @param divisor the value doing the dividing
     * @return the unsigned quotient of the first argument divided by
     * the second argument
     * @see #remainderUnsigned
     * @since 1.8
     */
    public static int divideUnsigned(int dividend, int divisor) {
        // In lieu of tricky code, for now just use long arithmetic.
        return (int)(toUnsignedLong(dividend) / toUnsignedLong(divisor));
    }

    
Returns the unsigned remainder from dividing the first argument
by the second where each argument and the result is interpreted
as an unsigned value.

Params:
  • dividend – the value to be divided
  • divisor – the value doing the dividing
See Also:
Returns:the unsigned remainder of the first argument divided by
the second argument
Since:1.8
/**
     * Returns the unsigned remainder from dividing the first argument
     * by the second where each argument and the result is interpreted
     * as an unsigned value.
     *
     * @param dividend the value to be divided
     * @param divisor the value doing the dividing
     * @return the unsigned remainder of the first argument divided by
     * the second argument
     * @see #divideUnsigned
     * @since 1.8
     */
    public static int remainderUnsigned(int dividend, int divisor) {
        // In lieu of tricky code, for now just use long arithmetic.
        return (int)(toUnsignedLong(dividend) % toUnsignedLong(divisor));
    }


    // Bit twiddling

    
The number of bits used to represent an int value in two's complement binary form. 
Since:1.5
/**
     * The number of bits used to represent an {@code int} value in two's
     * complement binary form.
     *
     * @since 1.5
     */
    @Native public static final int SIZE = 32;

    
The number of bytes used to represent an int value in two's complement binary form. 
Since:1.8
/**
     * The number of bytes used to represent an {@code int} value in two's
     * complement binary form.
     *
     * @since 1.8
     */
    public static final int BYTES = SIZE / Byte.SIZE;

    
Returns an int value with at most a single one-bit, in the position of the highest-order ("leftmost") one-bit in the specified 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. 
Params:
  • i – the value whose highest one bit is to be computed
Returns:an 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
/**
     * 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.
     *
     * @param i the value whose highest one bit is to be computed
     * @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) {
        return i & (MIN_VALUE >>> numberOfLeadingZeros(i));
    }

    
Returns an int value with at most a single one-bit, in the position of the lowest-order ("rightmost") one-bit in the specified 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. 
Params:
  • i – the value whose lowest one bit is to be computed
Returns:an 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
/**
     * 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.
     *
     * @param i the value whose lowest one bit is to be computed
     * @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 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. 
Note that this method is closely related to the logarithm base 2. For all positive int values x: 
    

  • floor(log2(x)) = 31 - numberOfLeadingZeros(x) 
  • ceil(log2(x)) = 32 - numberOfLeadingZeros(x - 1) 


Params:
  • i – the value whose number of leading zeros is to be computed
Returns:the number of zero bits preceding the highest-order ("leftmost") one-bit in the two's complement binary representation of the specified int value, or 32 if the value is equal to zero.
Since:1.5
/**
     * 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>
     *
     * @param i the value whose number of leading zeros is to be computed
     * @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
     */
    @IntrinsicCandidate
    public static int numberOfLeadingZeros(int i) {
        // HD, Count leading 0's
        if (i <= 0)
            return i == 0 ? 32 : 0;
        int n = 31;
        if (i >= 1 << 16) { n -= 16; i >>>= 16; }
        if (i >= 1 <<  8) { n -=  8; i >>>=  8; }
        if (i >= 1 <<  4) { n -=  4; i >>>=  4; }
        if (i >= 1 <<  2) { n -=  2; i >>>=  2; }
        return n - (i >>> 1);
    }

    
Returns the number of zero bits following the lowest-order ("rightmost") one-bit in the two's complement binary representation of the specified 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. 
Params:
  • i – the value whose number of trailing zeros is to be computed
Returns:the number of zero bits following the lowest-order ("rightmost") one-bit in the two's complement binary representation of the specified int value, or 32 if the value is equal to zero.
Since:1.5
/**
     * 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.
     *
     * @param i the value whose number of trailing zeros is to be computed
     * @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
     */
    @IntrinsicCandidate
    public static int numberOfTrailingZeros(int i) {
        // HD, Count trailing 0's
        i = ~i & (i - 1);
        if (i <= 0) return i & 32;
        int n = 1;
        if (i > 1 << 16) { n += 16; i >>>= 16; }
        if (i > 1 <<  8) { n +=  8; i >>>=  8; }
        if (i > 1 <<  4) { n +=  4; i >>>=  4; }
        if (i > 1 <<  2) { n +=  2; i >>>=  2; }
        return n + (i >>> 1);
    }

    
Returns the number of one-bits in the two's complement binary representation of the specified int value. This function is sometimes referred to as the population count.

Params:
  • i – the value whose bits are to be counted
Returns:the number of one-bits in the two's complement binary representation of the specified int value.
Since:1.5
/**
     * 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>.
     *
     * @param i the value whose bits are to be counted
     * @return the number of one-bits in the two's complement binary
     *     representation of the specified {@code int} value.
     * @since 1.5
     */
    @IntrinsicCandidate
    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 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.) 
Note that left rotation with a negative distance is equivalent to right rotation: 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: rotateLeft(val,
distance) == rotateLeft(val, distance & 0x1F). 
Params:
  • i – the value whose bits are to be rotated left
  • distance – the number of bit positions to rotate left
Returns:the value obtained by rotating the two's complement binary representation of the specified int value left by the specified number of bits.
Since:1.5
/**
     * 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)}.
     *
     * @param i the value whose bits are to be rotated left
     * @param distance the number of bit positions to rotate left
     * @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 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.) 
Note that right rotation with a negative distance is equivalent to left rotation: 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: rotateRight(val,
distance) == rotateRight(val, distance & 0x1F). 
Params:
  • i – the value whose bits are to be rotated right
  • distance – the number of bit positions to rotate right
Returns:the value obtained by rotating the two's complement binary representation of the specified int value right by the specified number of bits.
Since:1.5
/**
     * 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)}.
     *
     * @param i the value whose bits are to be rotated right
     * @param distance the number of bit positions to rotate right
     * @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 int value. 
Params:
  • i – the value to be reversed
Returns:the value obtained by reversing order of the bits in the specified int value.
Since:1.5
/**
     * Returns the value obtained by reversing the order of the bits in the
     * two's complement binary representation of the specified {@code int}
     * value.
     *
     * @param i the value to be reversed
     * @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;

        return reverseBytes(i);
    }

    
Returns the signum function of the specified 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.) 
Params:
  • i – the value whose signum is to be computed
Returns:the signum function of the specified int value.
Since:1.5
/**
     * 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.)
     *
     * @param i the value whose signum is to be computed
     * @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 int value. 
Params:
  • i – the value whose bytes are to be reversed
Returns:the value obtained by reversing the bytes in the specified int value.
Since:1.5
/**
     * Returns the value obtained by reversing the order of the bytes in the
     * two's complement representation of the specified {@code int} value.
     *
     * @param i the value whose bytes are to be reversed
     * @return the value obtained by reversing the bytes in the specified
     *     {@code int} value.
     * @since 1.5
     */
    @IntrinsicCandidate
    public static int reverseBytes(int i) {
        return (i << 24)            |
               ((i & 0xff00) << 8)  |
               ((i >>> 8) & 0xff00) |
               (i >>> 24);
    }

    
Adds two integers together as per the + operator.

Params:
  • a – the first operand
  • b – the second operand
See Also:
Returns:the sum of a and b
Since:1.8
/**
     * Adds two integers together as per the + operator.
     *
     * @param a the first operand
     * @param b the second operand
     * @return the sum of {@code a} and {@code b}
     * @see java.util.function.BinaryOperator
     * @since 1.8
     */
    public static int sum(int a, int b) {
        return a + b;
    }

    
Returns the greater of two int values as if by calling Math.max. 
Params:
  • a – the first operand
  • b – the second operand
See Also:
Returns:the greater of a and b
Since:1.8
/**
     * Returns the greater of two {@code int} values
     * as if by calling {@link Math#max(int, int) 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 int max(int a, int b) {
        return Math.max(a, b);
    }

    
Returns the smaller of two int values as if by calling Math.min. 
Params:
  • a – the first operand
  • b – the second operand
See Also:
Returns:the smaller of a and b
Since:1.8
/**
     * Returns the smaller of two {@code int} values
     * as if by calling {@link Math#min(int, int) 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 int min(int a, int b) {
        return Math.min(a, b);
    }

    
Returns an Optional containing the nominal descriptor for this instance, which is the instance itself. 
Returns:an Optional describing the Integer instance
Since:12
/**
     * Returns an {@link Optional} containing the nominal descriptor for this
     * instance, which is the instance itself.
     *
     * @return an {@link Optional} describing the {@linkplain Integer} instance
     * @since 12
     */
    @Override
    public Optional<Integer> describeConstable() {
        return Optional.of(this);
    }

    
Resolves this instance as a ConstantDesc, the result of which is the instance itself. 
Params:
  • lookup – ignored
Returns:the Integer instance
Since:12
/**
     * Resolves this instance as a {@link ConstantDesc}, the result of which is
     * the instance itself.
     *
     * @param lookup ignored
     * @return the {@linkplain Integer} instance
     * @since 12
     */
    @Override
    public Integer resolveConstantDesc(MethodHandles.Lookup lookup) {
        return this;
    }

    
use serialVersionUID from JDK 1.0.2 for interoperability 
/** use serialVersionUID from JDK 1.0.2 for interoperability */
    @java.io.Serial
    @Native private static final long serialVersionUID = 1360826667806852920L;
}