Serializable, Comparable<Long>, Constable, ConstantDesc
The
Long
class wraps a value of the primitive type
long
in an object. An object of type
Long
contains a single field whose type is
long
.
In addition, this class provides several methods for converting a long to a String and a String to a long, as well as other constants and methods useful when dealing with a long.
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).
Fields
static final int
The number of bytes used to represent a long value in two's complement binary form.
static final long
A constant holding the maximum value a long can have, 263-1.
static final long
A constant holding the minimum value a long can have, -263.
static final int
The number of bits used to represent a long value in two's complement binary form.
The Class instance representing the primitive type long.
Constructors
Deprecated, for removal: This API element is subject to removal in a future version. Deprecated, for removal: This API element is subject to removal in a future version.static int
Returns the number of one-bits in the two's complement binary representation of the specified long value.
byte
Returns the value of this Long as a byte after a narrowing primitive conversion.
static int
Compares two long values numerically.
int
Compares two Long objects numerically.
static int
Compares two long values numerically treating the values as unsigned.
static long
Returns the value obtained by compressing the bits of the specified long value, i, in accordance with the specified bit mask.
Decodes a String into a Long.
Returns an
Optional
containing the nominal descriptor for this instance, which is the instance itself.
static long
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
Returns the value of this Long as a double after a widening primitive conversion.
boolean
Compares this object to the specified object.
static long
Returns the value obtained by expanding the bits of the specified long value, i, in accordance with the specified bit mask.
float
Returns the value of this Long as a float after a widening primitive conversion.
Determines the long value of the system property with the specified name.
Determines the long value of the system property with the specified name.
Returns the long value of the system property with the specified name.
int
Returns a hash code for this Long.
static int
Returns a hash code for a long value; compatible with Long.hashCode().
static long
Returns a long value with at most a single one-bit, in the position of the highest-order ("leftmost") one-bit in the specified long value.
int
Returns the value of this Long as an int after a narrowing primitive conversion.
long
Returns the value of this Long as a long value.
static long
Returns a long value with at most a single one-bit, in the position of the lowest-order ("rightmost") one-bit in the specified long value.
static long
Returns the greater of two
long
values as if by calling
Math.max
.
static long
Returns the smaller of two
long
values as if by calling
Math.min
.
static int
Returns the number of zero bits preceding the highest-order ("leftmost") one-bit in the two's complement binary representation of the specified long value.
static int
Returns the number of zero bits following the lowest-order ("rightmost") one-bit in the two's complement binary representation of the specified long value.
static long
Parses the
CharSequence
argument as a signed
long
in the specified
radix
, beginning at the specified
beginIndex
and extending to
endIndex - 1
.
static long
Parses the string argument as a signed decimal long.
static long
Parses the string argument as a signed long in the radix specified by the second argument.
static long
Parses the
CharSequence
argument as an unsigned
long
in the specified
radix
, beginning at the specified
beginIndex
and extending to
endIndex - 1
.
static long
Parses the string argument as an unsigned decimal long.
static long
Parses the string argument as an unsigned long in the radix specified by the second argument.
static long
Returns the unsigned remainder from dividing the first argument by the second where each argument and the result is interpreted as an unsigned value.
Resolves this instance as a
ConstantDesc
, the result of which is the instance itself.
static long
Returns the value obtained by reversing the order of the bits in the two's complement binary representation of the specified long value.
static long
Returns the value obtained by reversing the order of the bytes in the two's complement representation of the specified long value.
static long
Returns the value obtained by rotating the two's complement binary representation of the specified long value left by the specified number of bits.
static long
Returns the value obtained by rotating the two's complement binary representation of the specified long value right by the specified number of bits.
short
Returns the value of this Long as a short after a narrowing primitive conversion.
static int
Returns the signum function of the specified long value.
static long
Adds two long values together as per the + operator.
Returns a string representation of the long argument as an unsigned integer in base 2.
Returns a string representation of the long argument as an unsigned integer in base 16.
Returns a string representation of the long argument as an unsigned integer in base 8.
Returns a String object representing this Long's value.
Returns a String object representing the specified long.
Returns a string representation of the first argument in the radix specified by the second argument.
Returns a string representation of the argument as an unsigned decimal value.
Returns a string representation of the first argument as an unsigned integer value in the radix specified by the second argument.
Returns a Long instance representing the specified long value.
Returns a Long object holding the value of the specified String.
Returns a Long object holding the value extracted from the specified String when parsed with the radix given by the second argument.
A constant holding the minimum value a long can have, -263.
A constant holding the maximum value a long can have, 263-1.
The Class instance representing the primitive type long.
The number of bits used to represent a long value in two's complement binary form.
public static final int BYTES
The number of bytes used to represent a long value in two's complement binary form.
Constructs a newly allocated Long object that represents the specified long argument.
value - the value to be represented by the Long object.
Constructs a newly allocated Long object that represents the long value indicated by the String parameter. The string is converted to a long value in exactly the manner used by the parseLong method for radix 10.
s - the String to be converted to a Long.
NumberFormatException - if the String does not contain a parsable long.
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 sign '-' ('\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
Nof these characters are used as radix-
Ndigits 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:
Long.toString(n, 16).toUpperCase()
i - a long to be converted to a string.
radix - the radix to use in the string representation.
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' ('\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.
Returns a string representation of the
long
argument as an unsigned integer in base 16.
The unsigned long value is the argument plus 264 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 Long.parseUnsignedLong(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:
Long.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 - a long to be converted to a string.
long value represented by the argument in hexadecimal (base 16).
Returns a string representation of the
long
argument as an unsigned integer in base 8.
The unsigned long value is the argument plus 264 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 Long.parseUnsignedLong(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 - a long to be converted to a string.
long value represented by the argument in octal (base 8).
Returns a string representation of the
long
argument as an unsigned integer in base 2.
The unsigned long value is the argument plus 264 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 Long.parseUnsignedLong(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 - a long to be converted to a string.
long value represented by the argument in binary (base 2).
Returns a
String
object representing the specified
long
. The argument is converted to signed decimal representation and returned as a string, exactly as if the argument and the radix 10 were given as arguments to the
toString(long, int)
method.
i - a long to be converted.
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(long, int)
method.
i - an integer to be converted to an unsigned string.
Parses the string argument as a signed
long
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
'-'
(
'\u002D'
) to indicate a negative value or an ASCII plus sign
'+'
(
'\u002B'
) to indicate a positive value. The resulting
long
value is returned.
Note that neither the character L ('\u004C') nor l ('\u006C') is permitted to appear at the end of the string as a type indicator, as would be permitted in Java programming language source code - except that either L or l may appear as a digit for a radix greater than or equal to 22.
An exception of type NumberFormatException is thrown if any of the following situations occurs:
null or is a string of length zero.radix is either smaller than Character.MIN_RADIX or larger than Character.MAX_RADIX.'-' ('\u002d') or plus sign '+' ('\u002B') provided that the string is longer than length 1.long.Examples:
parseLong("0", 10) returns 0L
parseLong("473", 10) returns 473L
parseLong("+42", 10) returns 42L
parseLong("-0", 10) returns 0L
parseLong("-FF", 16) returns -255L
parseLong("1100110", 2) returns 102L
parseLong("99", 8) throws a NumberFormatException
parseLong("Hazelnut", 10) throws a NumberFormatException
parseLong("Hazelnut", 36) returns 1356099454469L
s - the String containing the long representation to be parsed.
radix - the radix to be used while parsing s.
long represented by the string argument in the specified radix.
NumberFormatException - if the string does not contain a parsable long.
Parses the
CharSequence
argument as a signed
long
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 long representation to be parsed
beginIndex - the beginning index, inclusive.
endIndex - the ending index, exclusive.
radix - the radix to be used while parsing s.
long 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 long in the specified radix, or if radix is either smaller than Character.MIN_RADIX or larger than Character.MAX_RADIX.
Parses the string argument as a signed decimal
long
. The characters in the string must all be decimal digits, 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
long
value is returned, exactly as if the argument and the radix
10
were given as arguments to the
parseLong(java.lang.String, int)
method.
Note that neither the character L ('\u004C') nor l ('\u006C') is permitted to appear at the end of the string as a type indicator, as would be permitted in Java programming language source code.
s - a String containing the long representation to be parsed
long represented by the argument in decimal.
NumberFormatException - if the string does not contain a parsable long.
Parses the string argument as an unsigned
long
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
'+'
(
'\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.long, 264-1.s - the String containing the unsigned integer representation to be parsed
radix - the radix to be used while parsing s.
long represented by the string argument in the specified radix.
NumberFormatException - if the String does not contain a parsable long.
Parses the
CharSequence
argument as an unsigned
long
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 long representation to be parsed
beginIndex - the beginning index, inclusive.
endIndex - the ending index, exclusive.
radix - the radix to be used while parsing s.
long 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 long in the specified radix, or if radix is either smaller than Character.MIN_RADIX or larger than Character.MAX_RADIX.
Parses the string argument as an unsigned decimal
long
. The characters in the string must all be decimal digits, except that the first character may be an ASCII plus sign
'+'
(
'\u002B'
). The resulting integer value is returned, exactly as if the argument and the radix 10 were given as arguments to the
parseUnsignedLong(java.lang.String, int)
method.
s - a String containing the unsigned long representation to be parsed
long value represented by the decimal string argument
NumberFormatException - if the string does not contain a parsable unsigned integer.
Returns a
Long
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
long
in the radix specified by the second argument, exactly as if the arguments were given to the
parseLong(java.lang.String, int)
method. The result is a
Long
object that represents the
long
value specified by the string.
In other words, this method returns a Long object equal to the value of:
Long.valueOf(Long.parseLong(s, radix))
s - the string to be parsed
radix - the radix to be used in interpreting s
Long object holding the value represented by the string argument in the specified radix.
NumberFormatException - If the String does not contain a parsable long.
Returns a
Long
object holding the value of the specified
String
. The argument is interpreted as representing a signed decimal
long
, exactly as if the argument were given to the
parseLong(java.lang.String)
method. The result is a
Long
object that represents the integer value specified by the string.
In other words, this method returns a Long object equal to the value of:
Long.valueOf(Long.parseLong(s))
s - the string to be parsed.
Long object holding the value represented by the string argument.
NumberFormatException - If the string cannot be parsed as a long.
Returns a
Long
instance representing the specified
long
value. If a new
Long
instance is not required, this method should generally be used in preference to the constructor
Long(long)
, 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.
l - a long value.
Long instance representing l.
Decodes a
String
into a
Long
. Accepts decimal, hexadecimal, and octal numbers given by the following grammar:
DecimalNumeral
- DecodableString:
- Signopt DecimalNumeral
- Signopt
0xHexDigits- Signopt
0XHexDigits- Signopt
#HexDigits- Signopt
0OctalDigits- Sign:
-+
,
HexDigits, and
OctalDigitsare as defined in section
3.10.1of
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 Long.parseLong 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.
Long object holding the long value represented by nm
NumberFormatException - if the String does not contain a parsable long.
public byte byteValue()
Returns the value of this Long as a byte after a narrowing primitive conversion.
byteValue in class Number
byte.
public short shortValue()
Returns the value of this Long as a short after a narrowing primitive conversion.
shortValue in class Number
short.
public int intValue()
Returns the value of this Long as an int after a narrowing primitive conversion.
intValue in class Number
int.
public long longValue()
Returns the value of this Long as a long value.
public float floatValue()
Returns the value of this Long as a float after a widening primitive conversion.
floatValue in class Number
float.
public double doubleValue()
Returns the value of this Long as a double after a widening primitive conversion.
doubleValue in class Number
double.
Returns a
String
object representing this
Long
's value. The value is converted to signed decimal representation and returned as a string, exactly as if the
long
value were given as an argument to the
toString(long)
method.
public int hashCode()
Returns a hash code for this
Long
. The result is the exclusive OR of the two halves of the primitive
long
value held by this
Long
object. That is, the hashcode is the value of the expression:
(int)(this.longValue()^(this.longValue()>>>32))
public static int hashCode(long value)
Returns a hash code for a long value; compatible with Long.hashCode().
value - the value to hash
long value.
Compares this object to the specified object. The result is true if and only if the argument is not null and is a Long object that contains the same long value as this object.
Determines the
long
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(java.lang.String) method. The string value of this property is then interpreted as a long value using the grammar supported by decode and a Long 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 a Long object equal to the value of:
getLong(nm, null)
nm - property name.
Long value of the property.
SecurityException - for the same reasons as System.getProperty
Determines the
long
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(java.lang.String) method. The string value of this property is then interpreted as a long value using the grammar supported by decode and a Long object representing this value is returned.
The second argument is the default value. A Long 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 a Long object equal to the value of:
getLong(nm, Long.valueOf(val))
but in practice it may be implemented in a manner such as:
Long result = getLong(nm, null); return (result == null) ? Long.valueOf(val) : result;
to avoid the unnecessary allocation of a
Long
object when the default value is not needed.
nm - property name.
val - default value.
Long value of the property.
SecurityException - for the same reasons as System.getProperty
Returns the
long
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(java.lang.String)
method. The string value of this property is then interpreted as a
long
value, as per the
decode
method, and a
Long
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 for 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.Note that, in every case, neither L ('\u004C') nor l ('\u006C') is permitted to appear at the end of the property value as a type indicator, as would be permitted in Java programming language source code.
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.
Long value of the property.
SecurityException - for the same reasons as System.getProperty
Compares two Long objects numerically.
compareTo in interface Comparable<Long>
anotherLong - the Long to be compared.
0 if this Long is equal to the argument Long; a value less than 0 if this Long is numerically less than the argument Long; and a value greater than 0 if this Long is numerically greater than the argument Long (signed comparison).
public static int compare(long x, long y)
Compares two
long
values numerically. The value returned is identical to what would be returned by:
Long.valueOf(x).compareTo(Long.valueOf(y))
x - the first long to compare
y - the second long to compare
0 if x == y; a value less than 0 if x < y; and a value greater than 0 if x > y
public static int compareUnsigned(long x, long y)
Compares two long values numerically treating the values as unsigned.
x - the first long to compare
y - the second long to compare
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
public static long divideUnsigned(long dividend, long 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 divided
divisor - the value doing the dividing
public static long remainderUnsigned(long dividend, long 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.
dividend - the value to be divided
divisor - the value doing the dividing
public static long highestOneBit(long i)
Returns a long value with at most a single one-bit, in the position of the highest-order ("leftmost") one-bit in the specified long 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 computed
long 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 long lowestOneBit(long i)
Returns a long value with at most a single one-bit, in the position of the lowest-order ("rightmost") one-bit in the specified long 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 computed
long 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(long i)
Returns the number of zero bits preceding the highest-order ("leftmost") one-bit in the two's complement binary representation of the specified
long
value. Returns 64 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 long values x:
63 - numberOfLeadingZeros(x)64 - numberOfLeadingZeros(x - 1)i - the value whose number of leading zeros is to be computed
long value, or 64 if the value is equal to zero.
public static int numberOfTrailingZeros(long i)
Returns the number of zero bits following the lowest-order ("rightmost") one-bit in the two's complement binary representation of the specified long value. Returns 64 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 computed
long value, or 64 if the value is equal to zero.
public static int bitCount(long i)
Returns the number of one-bits in the two's complement binary representation of the specified long value. This function is sometimes referred to as the population count.
i - the value whose bits are to be counted
long value.
public static long rotateLeft(long i, int distance)
Returns the value obtained by rotating the two's complement binary representation of the specified
long
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 64 is a no-op, so all but the last six bits of the rotation distance can be ignored, even if the distance is negative: rotateLeft(val, distance) == rotateLeft(val, distance & 0x3F).
i - the value whose bits are to be rotated left
distance - the number of bit positions to rotate left
long value left by the specified number of bits.
public static long rotateRight(long i, int distance)
Returns the value obtained by rotating the two's complement binary representation of the specified
long
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 64 is a no-op, so all but the last six bits of the rotation distance can be ignored, even if the distance is negative: rotateRight(val, distance) == rotateRight(val, distance & 0x3F).
i - the value whose bits are to be rotated right
distance - the number of bit positions to rotate right
long value right by the specified number of bits.
public static long reverse(long i)
Returns the value obtained by reversing the order of the bits in the two's complement binary representation of the specified long value.
i - the value to be reversed
long value.
public static long compress(long i, long mask)
Returns the value obtained by compressing the bits of the specified
long
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(0xCAFEBABEL, 0xFF00FFF0L) == 0xCABABL
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, 1L << n) == (x >> n & 1)
// Logical shift right
compress(x, -1L << 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 : (1L << 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:
long compressLeft(long i, long mask) {
// This implementation follows the description in Hacker's Delight which
// is informative. A more optimal implementation is:
// Long.compress(i, mask) << -Long.bitCount(mask)
return Long.reverse(
Long.compress(Long.reverse(i), Long.reverse(mask)));
}
long sag(long i, long mask) {
return compressLeft(i, mask) | Long.compress(i, ~mask);
}
// Separate the sheep from the goats
sag(0x00000000_CAFEBABEL, 0xFFFFFFFF_FF00FFF0L) == 0x00000000_CABABFEEL
i - the value whose bits are to be compressed
mask - the bit mask
public static long expand(long i, long mask)
Returns the value obtained by expanding the bits of the specified
long
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(0x0000CABABL, 0xFF00FFF0L) == 0xCA00BAB0L
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, 1L << n) == (x & 1) << n
// Logically shift right
expand(x, -1L << n) == x << n
// Expanding all bits returns the mask
expand(-1L, 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 long value can be implemented as follows:
long select(long i, long n) {
// the one-bit in i (the mask) with index n
long nthBit = Long.expand(1L << n, i);
// the bit position of the one-bit with index n
return Long.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 expanded
mask - the bit mask
public static int signum(long i)
Returns the signum function of the specified long 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 computed
long value.
public static long reverseBytes(long i)
Returns the value obtained by reversing the order of the bytes in the two's complement representation of the specified long value.
i - the value whose bytes are to be reversed
long value.
public static long sum(long a, long b)
Adds two long values together as per the + operator.
a - the first operand
b - the second operand
a and b
public static long max(long a, long b)
Returns the greater of two
long
values as if by calling
Math.max
.
a - the first operand
b - the second operand
a and b
public static long min(long a, long b)
Returns the smaller of two
long
values as if by calling
Math.min
.
a - the first operand
b - the second operand
a and b
Returns an
Optional
containing the nominal descriptor for this instance, which is the instance itself.
describeConstable in interface Constable
Optional describing the Long instance
Resolves this instance as a
ConstantDesc
, the result of which is the instance itself.
resolveConstantDesc in interface ConstantDesc
lookup - ignored
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