/*

* Copyright (c) 1994, 2013, Oracle and/or its affiliates. All rights reserved.

* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*/

package java.lang;

import java.lang.annotation.Native;

/**

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

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

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

*

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

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

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

* dealing with an {@code int}.

*

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

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

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

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

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

*

* @author Lee Boynton

* @author Arthur van Hoff

* @author Josh Bloch

* @author Joseph D. Darcy

* @since JDK1.0

*/

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

/**

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

* have, -2³¹.

*/

@Native public static final int MIN_VALUE = 0x80000000;

/**

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

* have, 2³¹-1.

*/

@Native public static final int MAX_VALUE = 0x7fffffff;

/**

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

* {@code int}.

*

* @since JDK1.1

*/

@SuppressWarnings("unchecked")

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

/**

* All possible chars for representing a number as a String

*/

final static char[] digits = {

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

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

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

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

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

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

};

/**

* Returns a string representation of the first argument in the

* radix specified by the second argument.

*

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

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

* {@code 10} is used instead.

*

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

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

* ({@code '\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);

}

char buf[] = new char[33];

boolean negative = (i < 0);

int charPos = 32;

if (!negative) {

i = -i;

}

while (i <= -radix) {

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

i = i / radix;

}

buf[charPos] = digits[-i];

if (negative) {

buf[--charPos] = '-';

}

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

}

/**

* Returns a string representation of the 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&nbsp;16.

*

* <p>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&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>

*

* @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 #parseUnsignedInt(String, int)

* @see #toUnsignedString(int, int)

* @since JDK1.0.2

*/

public static String toHexString(int i) {

return toUnsignedString0(i, 4);

}

/**

* Returns a string representation of the integer argument as an

* unsigned integer in base&nbsp;8.

*

* <p>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&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 JDK1.0.2

*/

public static String toOctalString(int i) {

return toUnsignedString0(i, 3);

}

/**

* Returns a string representation of the integer argument as an

* unsigned integer in base&nbsp;2.

*

* <p>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&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 JDK1.0.2

*/

public static String toBinaryString(int i) {

return toUnsignedString0(i, 1);

}

/**

* Convert the integer to an unsigned number.

*/

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

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

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

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

char[] buf = new char[chars];

formatUnsignedInt(val, shift, buf, 0, chars);

// Use special constructor which takes over "buf".

return new String(buf, true);

}

/**

* Format a long (treated as unsigned) into a character buffer.

* @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 character buffer to write to

* @param offset the offset in the destination buffer to start at

* @param len the number of characters to write

* @return the lowest character location used

*/

static int formatUnsignedInt(int val, int shift, char[] buf, int offset, int len) {

int charPos = len;

int radix = 1 << shift;

int mask = radix - 1;

do {

buf[offset + --charPos] = Integer.digits[val & mask];

val >>>= shift;

} while (val != 0 && charPos > 0);

return charPos;

}

final static char [] DigitTens = {

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

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

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

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

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

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

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

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

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

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

} ;

final static char [] DigitOnes = {

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

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

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

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

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

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

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

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

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

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

} ;

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

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

// avoid division by 10.

//

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

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

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

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

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

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

//

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

// sequence.

//

// RE: Division by Invariant Integers using Multiplication

// T Gralund, P Montgomery

// ACM PLDI 1994

//

/**

* Returns a {@code String} object representing the

* specified integer. The argument is converted to signed decimal

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

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

* #toString(int, int)} method.

*

* @param i an integer to be converted.

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

*/

public static String toString(int i) {

if (i == Integer.MIN_VALUE)

return "-2147483648";

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

char[] buf = new char[size];

getChars(i, size, buf);

return new String(buf, true);

}

/**

* 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.

*

* Will fail if i == Integer.MIN_VALUE

*/

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

int q, r;

int charPos = index;

char sign = 0;

if (i < 0) {

sign = '-';

i = -i;

}

// Generate two digits per iteration

while (i >= 65536) {

q = i / 100;

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

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

i = q;

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

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

}

// Fall thru to fast mode for smaller numbers

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

for (;;) {

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

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

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

i = q;

if (i == 0) break;

}

if (sign != 0) {

buf [--charPos] = sign;

}

}

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

99999999, 999999999, Integer.MAX_VALUE };

// Requires positive x

static int stringSize(int x) {

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

if (x <= sizeTable[i])

return i+1;

}

/**

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

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

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

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

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

* ASCII minus sign {@code '-'} ({@code '\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.

* @exception NumberFormatException if the {@code String}

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

*/

public static int parseInt(String s, int radix)

throws NumberFormatException

{

/*

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

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

* the valueOf method.

*/

if (s == null) {

throw new NumberFormatException("null");

}

if (radix < Character.MIN_RADIX) {

throw new NumberFormatException("radix " + radix +

" less than Character.MIN_RADIX");

}

if (radix > Character.MAX_RADIX) {

throw new NumberFormatException("radix " + radix +

" greater than Character.MAX_RADIX");

}

int result = 0;

boolean negative = false;

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

int limit = -Integer.MAX_VALUE;

int multmin;

int digit;

if (len > 0) {

char firstChar = s.charAt(0);

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

if (firstChar == '-') {

negative = true;

limit = Integer.MIN_VALUE;

} else if (firstChar != '+')

throw NumberFormatException.forInputString(s);

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

throw NumberFormatException.forInputString(s);

i++;

}

multmin = limit / radix;

while (i < len) {

// Accumulating negatively avoids surprises near MAX_VALUE

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

if (digit < 0) {

throw NumberFormatException.forInputString(s);

}

if (result < multmin) {

throw NumberFormatException.forInputString(s);

}

result *= radix;

if (result < limit + digit) {

throw NumberFormatException.forInputString(s);

}

result -= digit;

}

} else {

throw NumberFormatException.forInputString(s);

}

return negative ? result : -result;

}

/**

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

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

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

* ({@code '\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.

* @exception 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 {@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}, 2³²-1.

*

* </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("null");

}

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);

}

}

/**

* 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 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 {@code Integer} object holding the value

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

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

* is interpreted as representing a signed integer in the radix

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

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

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

* represents the integer value specified by the string.

*

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

* object equal to the value of:

*

* <blockquote>

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

* </blockquote>

*

* @param s the string to be parsed.

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

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

* represented by the string argument in the specified

* radix.

* @exception NumberFormatException if the {@code String}

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

*/

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

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

}

/**

* Returns an {@code Integer} object holding the

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

* interpreted as representing a signed decimal integer, exactly

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

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

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

* specified by the string.

*

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

* object equal to the value of:

*

* <blockquote>

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

* </blockquote>

*

* @param s the string to be parsed.

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

* represented by the string argument.

* @exception NumberFormatException if the string cannot be parsed

* as an integer.

*/

public static Integer valueOf(String s) throws NumberFormatException {

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

}

/**

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

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

*

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

* may be controlled by the {@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

* sun.misc.VM class.

*/

private static class IntegerCache {

static final int low = -128;

static final int high;

static final Integer cache[];

static {

// high value may be configured by property

int h = 127;

String integerCacheHighPropValue =

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

if (integerCacheHighPropValue != null) {

try {

int i = parseInt(integerCacheHighPropValue);

i = Math.max(i, 127);

// Maximum array size is Integer.MAX_VALUE

h = Math.min(i, Integer.MAX_VALUE - (-low) -1);

} catch( NumberFormatException nfe) {

// If the property cannot be parsed into an int, ignore it.

}

}

high = h;

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

int j = low;

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

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

// range [-128, 127] must be interned (JLS7 5.1.7)

assert IntegerCache.high >= 127;

}

private IntegerCache() {}

}

/**

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

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

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

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

* to yield significantly better space and time performance by

* caching frequently requested values.

*

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

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

*

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

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

* @since 1.5

*/

public static Integer valueOf(int i) {

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

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

return new Integer(i);

}

/**

* The value of the {@code Integer}.

*

* @serial

*/

private final int value;

/**

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

* represents the specified {@code int} value.

*

* @param value the value to be represented by the

* {@code Integer} object.

*/

public Integer(int value) {

this.value = value;

}

/**

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

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

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

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

* {@code parseInt} method for radix 10.

*

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

* {@code Integer}.

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

* contain a parsable integer.

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

*/

public Integer(String s) throws NumberFormatException {

this.value = parseInt(s, 10);

}

/**

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

* after a narrowing primitive conversion.

* @jls 5.1.3 Narrowing Primitive Conversions

*/

public byte byteValue() {

return (byte)value;

}

/**

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

* after a narrowing primitive conversion.

* @jls 5.1.3 Narrowing Primitive Conversions

*/

public short shortValue() {

return (short)value;

}

/**

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

* {@code int}.

*/

public int intValue() {

return value;

}

/**

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

* after a widening primitive conversion.

* @jls 5.1.2 Widening Primitive Conversions

* @see Integer#toUnsignedLong(int)

*/

public long longValue() {

return (long)value;

}

/**

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

* after a widening primitive conversion.

* @jls 5.1.2 Widening Primitive Conversions

*/

public float floatValue() {

return (float)value;

}

/**

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

* after a widening primitive conversion.

* @jls 5.1.2 Widening Primitive Conversions

*/

public double doubleValue() {

return (double)value;

}

/**

* Returns a {@code String} object representing this

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

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

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

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

*

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

* base&nbsp;10.

*/

public String toString() {

return toString(value);

}

/**

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

*

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

* primitive {@code int} value represented by this

* {@code Integer} object.

*/

@Override

public int hashCode() {

return Integer.hashCode(value);

}

/**

* Returns a hash code for a {@code int} value; compatible with

* {@code Integer.hashCode()}.

*

* @param value the value to hash

* @since 1.8

*

* @return a hash code value for a {@code int} value.

*/

public static int hashCode(int value) {

return value;

}

/**

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

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

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

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

*

* @param obj the object to compare with.

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

* {@code false} otherwise.

*/

public boolean equals(Object obj) {

if (obj instanceof Integer) {

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

}

return false;

}

/**

* Determines the integer value of the system property with the

* specified name.

*

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

* property. System properties are accessible through the {@link

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

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

* value 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)}