Serializable, Comparable<Integer>, Constable, ConstantDesc
public final class Integer extends Number implements Comparable<Integer>, Constable, ConstantDesc
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).
| Modifier and Type | Field | Description |
|---|---|---|
static final int |
BYTES |
The number of bytes used to represent an int value in two's complement binary form. |
static final int |
MAX_VALUE |
A constant holding the maximum value an int can have, 231-1. |
static final int |
MIN_VALUE |
A constant holding the minimum value an int can have, -231. |
static final int |
SIZE |
The number of bits used to represent an int value in two's complement binary form. |
static final Class |
TYPE |
The Class instance representing the primitive type int. |
| Constructor | Description |
|---|---|
Integer |
Deprecated, for removal: This API element is subject to removal in a future version. It is rarely appropriate to use this constructor. |
Integer |
Deprecated, for removal: This API element is subject to removal in a future version. It is rarely appropriate to use this constructor. |
| Modifier and Type | Method | Description |
|---|---|---|
static int |
bitCount |
Returns the number of one-bits in the two's complement binary representation of the specified int value. |
byte |
byteValue() |
Returns the value of this Integer as a byte after a narrowing primitive conversion. |
static int |
compare |
Compares two int values numerically. |
int |
compareTo |
Compares two Integer objects numerically. |
static int |
compareUnsigned |
Compares two int values numerically treating the values as unsigned. |
static int |
compress |
Returns the value obtained by compressing the bits of the specified int value, i, in accordance with the specified bit mask. |
static Integer |
decode |
Decodes a String into an Integer. |
Optional |
describeConstable() |
Returns an Optional containing the nominal descriptor for this instance, which is the instance itself. |
static int |
divideUnsigned |
Returns the unsigned quotient of dividing the first argument by the second where each argument and the result is interpreted as an unsigned value. |
double |
doubleValue() |
Returns the value of this Integer as a double after a widening primitive conversion. |
boolean |
equals |
Compares this object to the specified object. |
static int |
expand |
Returns the value obtained by expanding the bits of the specified int value, i, in accordance with the specified bit mask. |
float |
floatValue() |
Returns the value of this Integer as a float after a widening primitive conversion. |
static Integer |
getInteger |
Determines the integer value of the system property with the specified name. |
static Integer |
getInteger |
Determines the integer value of the system property with the specified name. |
static Integer |
getInteger |
Returns the integer value of the system property with the specified name. |
int |
hashCode() |
Returns a hash code for this Integer. |
static int |
hashCode |
Returns a hash code for an int value; compatible with Integer.hashCode(). |
static int |
highestOneBit |
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. |
int |
intValue() |
Returns the value of this Integer as an int. |
long |
longValue() |
Returns the value of this Integer as a long after a widening primitive conversion. |
static int |
lowestOneBit |
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. |
static int |
max |
Returns the greater of two int values as if by calling Math.max. |
static int |
min |
Returns the smaller of two int values as if by calling Math.min. |
static int |
numberOfLeadingZeros |
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. |
static int |
numberOfTrailingZeros |
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. |
static int |
parseInt |
Parses the CharSequence argument as a signed int in the specified radix, beginning at the specified beginIndex and extending to endIndex - 1. |
static int |
parseInt |
Parses the string argument as a signed decimal integer. |
static int |
parseInt |
Parses the string argument as a signed integer in the radix specified by the second argument. |
static int |
parseUnsignedInt |
Parses the CharSequence argument as an unsigned int in the specified radix, beginning at the specified beginIndex and extending to endIndex - 1. |
static int |
parseUnsignedInt |
Parses the string argument as an unsigned decimal integer. |
static int |
parseUnsignedInt |
Parses the string argument as an unsigned integer in the radix specified by the second argument. |
static int |
remainderUnsigned |
Returns the unsigned remainder from dividing the first argument by the second where each argument and the result is interpreted as an unsigned value. |
Integer |
resolveConstantDesc |
Resolves this instance as a ConstantDesc, the result of which is the instance itself. |
static int |
reverse |
Returns the value obtained by reversing the order of the bits in the two's complement binary representation of the specified int value. |
static int |
reverseBytes |
Returns the value obtained by reversing the order of the bytes in the two's complement representation of the specified int value. |
static int |
rotateLeft |
Returns the value obtained by rotating the two's complement binary representation of the specified int value left by the specified number of bits. |
static int |
rotateRight |
Returns the value obtained by rotating the two's complement binary representation of the specified int value right by the specified number of bits. |
short |
shortValue() |
Returns the value of this Integer as a short after a narrowing primitive conversion. |
static int |
signum |
Returns the signum function of the specified int value. |
static int |
sum |
Adds two integers together as per the + operator. |
static String |
toBinaryString |
Returns a string representation of the integer argument as an unsigned integer in base 2. |
static String |
toHexString |
Returns a string representation of the integer argument as an unsigned integer in base 16. |
static String |
toOctalString |
Returns a string representation of the integer argument as an unsigned integer in base 8. |
String |
toString() |
Returns a String object representing this Integer's value. |
static String |
toString |
Returns a String object representing the specified integer. |
static String |
toString |
Returns a string representation of the first argument in the radix specified by the second argument. |
static long |
toUnsignedLong |
Converts the argument to a long by an unsigned conversion. |
static String |
toUnsignedString |
Returns a string representation of the argument as an unsigned decimal value. |
static String |
toUnsignedString |
Returns a string representation of the first argument as an unsigned integer value in the radix specified by the second argument. |
static Integer |
valueOf |
Returns an Integer instance representing the specified int value. |
static Integer |
valueOf |
Returns an Integer object holding the value of the specified String. |
static Integer |
valueOf |
Returns an Integer object holding the value extracted from the specified String when parsed with the radix given by the second argument. |
@Native public static final int MIN_VALUE
int can have, -231.@Native public static final int MAX_VALUE
int can have, 231-1.public static final Class<Integer> TYPE
Class instance representing the primitive type int.@Native public static final int SIZE
int value in two's complement binary form.public static final int BYTES
int value in two's complement binary form.@Deprecated(since="9", forRemoval=true) public Integer(int value)
valueOf(int) is generally a better choice, as it is likely to yield significantly better space and time performance.Integer object that represents the specified int value.value - the value to be represented by the Integer object.@Deprecated(since="9", forRemoval=true) public Integer(String s) throws NumberFormatException
parseInt(String) to convert a string to a int primitive, or use valueOf(String) to convert a string to an Integer object.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.s - the String to be converted to an Integer.NumberFormatException - if the String does not contain a parsable integer.public static String toString(int i, int radix)
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 '-' ('\u002D'). 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' ('\u0030'); 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 '\u0030' through '\u0039' and '\u0061' through '\u007A'. 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()
i - an integer to be converted to a string.radix - the radix to use in the string representation.public static String toUnsignedString(int i, int radix)
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' ('\u0030'); 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.
i - an integer to be converted to an unsigned string.radix - the radix to use in the string representation.public static String toHexString(int i)
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' ('\u0030'); 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 '\u0030' through '\u0039' and '\u0061' through '\u0066'. If uppercase letters are desired, the String.toUpperCase() method may be called on the result: Integer.toHexString(n).toUpperCase()
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.i - an integer to be converted to a string.public static String toOctalString(int i)
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' ('\u0030'); 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 '\u0030' through '\u0037'.i - an integer to be converted to a string.public static String toBinaryString(int i)
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' ('\u0030'); otherwise, the first character of the representation of the unsigned magnitude will not be the zero character. The characters '0' ('\u0030') and
'1' ('\u0031') are used as binary digits.
i - an integer to be converted to a string.public static String toString(int i)
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.i - an integer to be converted.public static String toUnsignedString(int i)
toUnsignedString(int, int) method.i - an integer to be converted to an unsigned string.public static int parseInt(String s, int radix) throws NumberFormatException
Character.digit(char, int) returns a nonnegative value), except that the first character may be an ASCII minus sign '-' ('\u002D') to indicate a negative value or an ASCII plus sign '+' ('\u002B') 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:
null or is a string of length zero. Character.MIN_RADIX or larger than Character.MAX_RADIX. '-' ('\u002D') or plus sign '+' ('\u002B') provided that the string is longer than length 1. 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
s - the String containing the integer representation to be parsedradix - the radix to be used while parsing s.NumberFormatException - if the String does not contain a parsable int.public static int parseInt(CharSequence s, int beginIndex, int endIndex, int radix) throws NumberFormatException
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.
s - the CharSequence containing the int representation to be parsedbeginIndex - the beginning index, inclusive.endIndex - the ending index, exclusive.radix - the radix to be used while parsing s.int represented by the subsequence in the specified radix.NullPointerException - if s is null.IndexOutOfBoundsException - if beginIndex is negative, or if beginIndex is greater than endIndex or if endIndex is greater than s.length().NumberFormatException - if the CharSequence does not contain a parsable int in the specified radix, or if radix is either smaller than Character.MIN_RADIX or larger than Character.MAX_RADIX.public static int parseInt(String s) throws NumberFormatException
'-' ('\u002D') to indicate a negative value or an ASCII plus sign '+' ('\u002B') 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(java.lang.String, int) method.s - a String containing the int representation to be parsedNumberFormatException - if the string does not contain a parsable integer.public static int parseUnsignedInt(String s, int radix) throws NumberFormatException
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 '+' ('\u002B'). The resulting integer value is returned. An exception of type NumberFormatException is thrown if any of the following situations occurs:
null or is a string of length zero. Character.MIN_RADIX or larger than Character.MAX_RADIX. '+' ('\u002B') provided that the string is longer than length 1. int, 232-1. s - the String containing the unsigned integer representation to be parsedradix - the radix to be used while parsing s.NumberFormatException - if the String does not contain a parsable int.public static int parseUnsignedInt(CharSequence s, int beginIndex, int endIndex, int radix) throws NumberFormatException
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.
s - the CharSequence containing the unsigned int representation to be parsedbeginIndex - the beginning index, inclusive.endIndex - the ending index, exclusive.radix - the radix to be used while parsing s.int represented by the subsequence in the specified radix.NullPointerException - if s is null.IndexOutOfBoundsException - if beginIndex is negative, or if beginIndex is greater than endIndex or if endIndex is greater than s.length().NumberFormatException - if the CharSequence does not contain a parsable unsigned int in the specified radix, or if radix is either smaller than Character.MIN_RADIX or larger than Character.MAX_RADIX.public static int parseUnsignedInt(String s) throws NumberFormatException
'+' ('\u002B'). The resulting integer value is returned, exactly as if the argument and the radix 10 were given as arguments to the parseUnsignedInt(java.lang.String, int) method.s - a String containing the unsigned int representation to be parsedNumberFormatException - if the string does not contain a parsable unsigned integer.public static Integer valueOf(String s, int radix) throws NumberFormatException
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(java.lang.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:
Integer.valueOf(Integer.parseInt(s, radix))
s - the string to be parsed.radix - the radix to be used in interpreting s
Integer object holding the value represented by the string argument in the specified radix.NumberFormatException - if the String does not contain a parsable int.public static Integer valueOf(String s) throws NumberFormatException
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(java.lang.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:
Integer.valueOf(Integer.parseInt(s))
s - the string to be parsed.Integer object holding the value represented by the string argument.NumberFormatException - if the string cannot be parsed as an integer.public static Integer valueOf(int i)
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.i - an int value.Integer instance representing i.public byte byteValue()
Integer as a byte after a narrowing primitive conversion.byteValue in class Number
byte.public short shortValue()
Integer as a short after a narrowing primitive conversion.shortValue in class Number
short.public int intValue()
Integer as an int.public long longValue()
Integer as a long after a widening primitive conversion.longValue in class Number
long.public float floatValue()
Integer as a float after a widening primitive conversion.floatValue in class Number
float.public double doubleValue()
Integer as a double after a widening primitive conversion.doubleValue in class Number
double.public String toString()
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.public int hashCode()
Integer.public static int hashCode(int value)
int value; compatible with Integer.hashCode().value - the value to hashint value.public boolean equals(Object obj)
true if and only if the argument is not null and is an Integer object that contains the same int value as this object.public static Integer getInteger(String nm)
The first argument is treated as the name of a system property. System properties are accessible through the System.getProperty(java.lang.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)
nm - property name.Integer value of the property.SecurityException - for the same reasons as System.getProperty
public static Integer getInteger(String nm, int val)
The first argument is treated as the name of a system property. System properties are accessible through the System.getProperty(java.lang.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, Integer.valueOf(val)) but in practice it may be implemented in a manner such as: to avoid the unnecessary allocation of anInteger result = getInteger(nm, null); return (result == null) ? Integer.valueOf(val) : result;
Integer object when the default value is not needed.nm - property name.val - default value.Integer value of the property.SecurityException - for the same reasons as System.getProperty
public static Integer getInteger(String nm, Integer val)
System.getProperty(java.lang.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: 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(java.lang.String, int) with radix 16. 0 followed by another character, it is parsed as an octal integer exactly as by the method valueOf(java.lang.String, int) with radix 8. valueOf(java.lang.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.
nm - property name.val - default value.Integer value of the property.SecurityException - for the same reasons as System.getProperty
public static Integer decode(String nm) throws NumberFormatException
String into an Integer. Accepts decimal, hexadecimal, and octal numbers given by the following grammar: DecimalNumeral, HexDigits, and OctalDigits are as defined in section 3.10.1 of The Java Language Specification, except that underscores are not accepted between digits.
- DecodableString:
- Signopt DecimalNumeral
- Signopt
0xHexDigits- Signopt
0XHexDigits- Signopt
#HexDigits- Signopt
0OctalDigits- Sign:
-+
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.
nm - the String to decode.Integer object holding the int value represented by nm
NumberFormatException - if the String does not contain a parsable integer.public int compareTo(Integer anotherInteger)
Integer objects numerically.compareTo in interface Comparable<Integer>
anotherInteger - the Integer to be compared.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).public static int compare(int x, int y)
int values numerically. The value returned is identical to what would be returned by:
Integer.valueOf(x).compareTo(Integer.valueOf(y))
x - the first int to comparey - the second int to compare0 if x == y; a value less than 0 if x < y; and a value greater than 0 if x > y
public static int compareUnsigned(int x, int y)
int values numerically treating the values as unsigned.x - the first int to comparey - the second int to compare0 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 valuespublic static long toUnsignedLong(int x)
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.x - the value to convert to an unsigned long
long by an unsigned conversionpublic static int divideUnsigned(int dividend, int divisor)
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.
dividend - the value to be divideddivisor - the value doing the dividingpublic static int remainderUnsigned(int dividend, int divisor)
dividend - the value to be divideddivisor - the value doing the dividingpublic static int highestOneBit(int i)
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.i - the value whose highest one bit is to be computedint 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.public static int lowestOneBit(int i)
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.i - the value whose lowest one bit is to be computedint 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.public static int numberOfLeadingZeros(int i)
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:
31 - numberOfLeadingZeros(x) 32 - numberOfLeadingZeros(x - 1) i - the value whose number of leading zeros is to be computedint value, or 32 if the value is equal to zero.public static int numberOfTrailingZeros(int i)
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.i - the value whose number of trailing zeros is to be computedint value, or 32 if the value is equal to zero.public static int bitCount(int i)
int value. This function is sometimes referred to as the population count.i - the value whose bits are to be countedint value.public static int rotateLeft(int i, int distance)
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).
i - the value whose bits are to be rotated leftdistance - the number of bit positions to rotate leftint value left by the specified number of bits.public static int rotateRight(int i, int distance)
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).
i - the value whose bits are to be rotated rightdistance - the number of bit positions to rotate rightint value right by the specified number of bits.public static int reverse(int i)
int value.i - the value to be reversedint value.public static int compress(int i, int mask)
int value, i, in accordance with the specified bit mask. For each one-bit value mb of the mask, from least significant to most significant, the bit value of i at the same bit location as mb is assigned to the compressed value contiguously starting from the least significant bit location. All the upper remaining bits of the compressed value are set to zero.
// Compressing drink to food
compress(0xCAFEBABE, 0xFF00FFF0) == 0xCABAB
0xFF00FFF0 selects hexadecimal digits at positions 1, 2, 3, 6 and 7 of 0xCAFEBABE. The selected digits occur in the resulting compressed value contiguously from digit position 0 in the same order. The following identities all return true and are helpful to understand the behaviour of compress:
// Returns 1 if the bit at position n is one
compress(x, 1 << n) == (x >> n & 1)
// Logical shift right
compress(x, -1 << n) == x >>> n
// Any bits not covered by the mask are ignored
compress(x, m) == compress(x & m, m)
// Compressing a value by itself
compress(m, m) == (m == -1 || m == 0) ? m : (1 << bitCount(m)) - 1
// Expanding then compressing with the same mask
compress(expand(x, m), m) == x & compress(m, m)
The Sheep And Goats (SAG) operation (see Hacker's Delight, section 7.7) can be implemented as follows:
int compressLeft(int i, int mask) {
// This implementation follows the description in Hacker's Delight which
// is informative. A more optimal implementation is:
// Integer.compress(i, mask) << -Integer.bitCount(mask)
return Integer.reverse(
Integer.compress(Integer.reverse(i), Integer.reverse(mask)));
}
int sag(int i, int mask) {
return compressLeft(i, mask) | Integer.compress(i, ~mask);
}
// Separate the sheep from the goats
sag(0xCAFEBABE, 0xFF00FFF0) == 0xCABABFEE
i - the value whose bits are to be compressedmask - the bit maskpublic static int expand(int i, int mask)
int value, i, in accordance with the specified bit mask. For each one-bit value mb of the mask, from least significant to most significant, the next contiguous bit value of i starting at the least significant bit is assigned to the expanded value at the same bit location as mb. All other remaining bits of the expanded value are set to zero.
expand(0x0000CABAB, 0xFF00FFF0) == 0xCA00BAB0
0xFF00FFF0 selects the first five hexadecimal digits of 0x0000CABAB. The selected digits occur in the resulting expanded value in order at positions 1, 2, 3, 6, and 7. The following identities all return true and are helpful to understand the behaviour of expand:
// Logically shift right the bit at position 0
expand(x, 1 << n) == (x & 1) << n
// Logically shift right
expand(x, -1 << n) == x << n
// Expanding all bits returns the mask
expand(-1, m) == m
// Any bits not covered by the mask are ignored
expand(x, m) == expand(x, m) & m
// Compressing then expanding with the same mask
expand(compress(x, m), m) == x & m
The select operation for determining the position of the one-bit with index n in a int value can be implemented as follows:
int select(int i, int n) {
// the one-bit in i (the mask) with index n
int nthBit = Integer.expand(1 << n, i);
// the bit position of the one-bit with index n
return Integer.numberOfTrailingZeros(nthBit);
}
// The one-bit with index 0 is at bit position 1
select(0b10101010_10101010, 0) == 1
// The one-bit with index 3 is at bit position 7
select(0b10101010_10101010, 3) == 7
i - the value whose bits are to be expandedmask - the bit maskpublic static int signum(int i)
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.)i - the value whose signum is to be computedint value.public static int reverseBytes(int i)
int value.i - the value whose bytes are to be reversedint value.public static int sum(int a, int b)
a - the first operandb - the second operanda and b
public static int max(int a, int b)
int values as if by calling Math.max.a - the first operandb - the second operanda and b
public static int min(int a, int b)
int values as if by calling Math.min.a - the first operandb - the second operanda and b
public Optional<Integer> describeConstable()
Optional containing the nominal descriptor for this instance, which is the instance itself.describeConstable in interface Constable
Optional describing the Integer instancepublic Integer resolveConstantDesc(MethodHandles.Lookup lookup)
ConstantDesc, the result of which is the instance itself.resolveConstantDesc in interface ConstantDesc
lookup - ignored
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