Serializable
, Comparable<Long>
, Constable
, ConstantDesc
public final class Long extends Number implements Comparable<Long>, Constable, ConstantDesc
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).
Modifier and Type | Field | Description |
---|---|---|
static final int |
BYTES |
The number of bytes used to represent a long value in two's complement binary form. |
static final long |
MAX_VALUE |
A constant holding the maximum value a long can have, 263-1. |
static final long |
MIN_VALUE |
A constant holding the minimum value a long can have, -263. |
static final int |
SIZE |
The number of bits used to represent a long value in two's complement binary form. |
static final Class |
TYPE |
The Class instance representing the primitive type long . |
Constructor | Description |
---|---|
Long |
Deprecated, for removal: This API element is subject to removal in a future version. It is rarely appropriate to use this constructor. |
Long |
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 long value. |
byte |
byteValue() |
Returns the value of this Long as a byte after a narrowing primitive conversion. |
static int |
compare |
Compares two long values numerically. |
int |
compareTo |
Compares two Long objects numerically. |
static int |
compareUnsigned |
Compares two long values numerically treating the values as unsigned. |
static long |
compress |
Returns the value obtained by compressing the bits of the specified long value, i , in accordance with the specified bit mask. |
static Long |
decode |
Decodes a String into a Long . |
Optional |
describeConstable() |
Returns an Optional containing the nominal descriptor for this instance, which is the instance itself. |
static long |
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 Long as a double after a widening primitive conversion. |
boolean |
equals |
Compares this object to the specified object. |
static long |
expand |
Returns the value obtained by expanding the bits of the specified long value, i , in accordance with the specified bit mask. |
float |
floatValue() |
Returns the value of this Long as a float after a widening primitive conversion. |
static Long |
getLong |
Determines the long value of the system property with the specified name. |
static Long |
getLong |
Determines the long value of the system property with the specified name. |
static Long |
getLong |
Returns the long value of the system property with the specified name. |
int |
hashCode() |
Returns a hash code for this Long . |
static int |
hashCode |
Returns a hash code for a long value; compatible with Long.hashCode() . |
static long |
highestOneBit |
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 |
intValue() |
Returns the value of this Long as an int after a narrowing primitive conversion. |
long |
longValue() |
Returns the value of this Long as a long value. |
static long |
lowestOneBit |
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 |
max |
Returns the greater of two long values as if by calling Math.max . |
static long |
min |
Returns the smaller of two long 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 long 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 long value. |
static long |
parseLong |
Parses the CharSequence argument as a signed long in the specified radix , beginning at the specified beginIndex and extending to endIndex - 1 . |
static long |
parseLong |
Parses the string argument as a signed decimal long . |
static long |
parseLong |
Parses the string argument as a signed long in the radix specified by the second argument. |
static long |
parseUnsignedLong |
Parses the CharSequence argument as an unsigned long in the specified radix , beginning at the specified beginIndex and extending to endIndex - 1 . |
static long |
parseUnsignedLong |
Parses the string argument as an unsigned decimal long . |
static long |
parseUnsignedLong |
Parses the string argument as an unsigned long in the radix specified by the second argument. |
static long |
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. |
Long |
resolveConstantDesc |
Resolves this instance as a ConstantDesc , the result of which is the instance itself. |
static long |
reverse |
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 |
reverseBytes |
Returns the value obtained by reversing the order of the bytes in the two's complement representation of the specified long value. |
static long |
rotateLeft |
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 |
rotateRight |
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 |
shortValue() |
Returns the value of this Long as a short after a narrowing primitive conversion. |
static int |
signum |
Returns the signum function of the specified long value. |
static long |
sum |
Adds two long values together as per the + operator. |
static String |
toBinaryString |
Returns a string representation of the long argument as an unsigned integer in base 2. |
static String |
toHexString |
Returns a string representation of the long argument as an unsigned integer in base 16. |
static String |
toOctalString |
Returns a string representation of the long argument as an unsigned integer in base 8. |
String |
toString() |
Returns a String object representing this Long 's value. |
static String |
toString |
Returns a String object representing the specified long . |
static String |
toString |
Returns a string representation of the first argument in the radix specified by the second argument. |
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 Long |
valueOf |
Returns a Long instance representing the specified long value. |
static Long |
valueOf |
Returns a Long object holding the value of the specified String . |
static Long |
valueOf |
Returns a Long object holding the value extracted from the specified String when parsed with the radix given by the second argument. |
@Native public static final long MIN_VALUE
long
can have, -263.@Native public static final long MAX_VALUE
long
can have, 263-1.public static final Class<Long> TYPE
Class
instance representing the primitive type long
.@Native public static final int SIZE
long
value in two's complement binary form.public static final int BYTES
long
value in two's complement binary form.@Deprecated(since="9", forRemoval=true) public Long(long value)
valueOf(long)
is generally a better choice, as it is likely to yield significantly better space and time performance.Long
object that represents the specified long
argument.value
- the value to be represented by the Long
object.@Deprecated(since="9", forRemoval=true) public Long(String s) throws NumberFormatException
parseLong(String)
to convert a string to a long
primitive, or use valueOf(String)
to convert a string to a Long
object.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
.public static String toString(long 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 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 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: Long.toString(n, 16).toUpperCase()
i
- a long
to be converted to a string.radix
- the radix to use in the string representation.public static String toUnsignedString(long 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(long i)
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 0
s.
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).public static String toOctalString(long i)
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 0
s.
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).public static String toBinaryString(long i)
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 0
s.
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).public static String toString(long i)
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.public static String toUnsignedString(long i)
toUnsignedString(long, int)
method.i
- an integer to be converted to an unsigned string.public static long parseLong(String s, int radix) throws NumberFormatException
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
.public static long parseLong(CharSequence s, int beginIndex, int endIndex, int radix) throws NumberFormatException
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 parsedbeginIndex
- 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
.public static long parseLong(String s) throws NumberFormatException
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 parsedlong
represented by the argument in decimal.NumberFormatException
- if the string does not contain a parsable long
.public static long parseUnsignedLong(String s, int radix) throws NumberFormatException
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 parsedradix
- 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
.public static long parseUnsignedLong(CharSequence s, int beginIndex, int endIndex, int radix) throws NumberFormatException
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 parsedbeginIndex
- 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
.public static long parseUnsignedLong(String s) throws NumberFormatException
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 parsedlong
value represented by the decimal string argumentNumberFormatException
- if the string does not contain a parsable unsigned integer.public static Long valueOf(String s, int radix) throws NumberFormatException
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 parsedradix
- 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
.public static Long valueOf(String s) throws NumberFormatException
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
.public static Long valueOf(long l)
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
.public static Long decode(String nm) throws NumberFormatException
String
into a Long
. 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
0x
HexDigits- Signopt
0X
HexDigits- Signopt
#
HexDigits- Signopt
0
OctalDigits- Sign:
-
+
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()
Long
as a byte
after a narrowing primitive conversion.byteValue
in class Number
byte
.public short shortValue()
Long
as a short
after a narrowing primitive conversion.shortValue
in class Number
short
.public int intValue()
Long
as an int
after a narrowing primitive conversion.intValue
in class Number
int
.public long longValue()
Long
as a long
value.public float floatValue()
Long
as a float
after a widening primitive conversion.floatValue
in class Number
float
.public double doubleValue()
Long
as a double
after a widening primitive conversion.doubleValue
in class Number
double
.public String toString()
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()
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)
long
value; compatible with Long.hashCode()
.value
- the value to hashlong
value.public boolean equals(Object obj)
true
if and only if the argument is not null
and is a Long
object that contains the same long
value as this object.public static Long getLong(String nm)
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
public static Long getLong(String nm, long val)
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: to avoid the unnecessary allocation of aLong result = getLong(nm, null); return (result == null) ? Long.valueOf(val) : result;
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
public static Long getLong(String nm, Long val)
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
public int compareTo(Long anotherLong)
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)
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 comparey
- the second long
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(long x, long y)
long
values numerically treating the values as unsigned.x
- the first long
to comparey
- the second long
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 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 divideddivisor
- the value doing the dividingpublic static long remainderUnsigned(long dividend, long divisor)
dividend
- the value to be divideddivisor
- the value doing the dividingpublic static long highestOneBit(long i)
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 computedlong
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)
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 computedlong
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)
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 computedlong
value, or 64 if the value is equal to zero.public static int numberOfTrailingZeros(long i)
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 computedlong
value, or 64 if the value is equal to zero.public static int bitCount(long i)
long
value. This function is sometimes referred to as the population count.i
- the value whose bits are to be countedlong
value.public static long rotateLeft(long i, int distance)
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 leftdistance
- the number of bit positions to rotate leftlong
value left by the specified number of bits.public static long rotateRight(long i, int distance)
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 rightdistance
- the number of bit positions to rotate rightlong
value right by the specified number of bits.public static long reverse(long i)
long
value.i
- the value to be reversedlong
value.public static long compress(long i, long mask)
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 compressedmask
- the bit maskpublic static long expand(long i, long mask)
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 expandedmask
- the bit maskpublic static int signum(long i)
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 computedlong
value.public static long reverseBytes(long i)
long
value.i
- the value whose bytes are to be reversedlong
value.public static long sum(long a, long b)
long
values together as per the + operator.a
- the first operandb
- the second operanda
and b
public static long max(long a, long b)
long
values as if by calling Math.max
.a
- the first operandb
- the second operanda
and b
public static long min(long a, long b)
long
values as if by calling Math.min
.a
- the first operandb
- the second operanda
and b
public Optional<Long> describeConstable()
Optional
containing the nominal descriptor for this instance, which is the instance itself.describeConstable
in interface Constable
Optional
describing the Long instancepublic Long resolveConstantDesc(MethodHandles.Lookup lookup)
ConstantDesc
, the result of which is the instance itself.resolveConstantDesc
in interface ConstantDesc
lookup
- ignored
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Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
Various third party code in OpenJDK is licensed under different licenses (see Debian package).
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https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/lang/Long.html