Class Long
- All Implemented Interfaces:
Serializable,Comparable<Long>,Constable,ConstantDesc
Long class is thewrapper class for values of the primitivetypelong. An object of typeLong contains asingle field whose type islong. In addition, this class provides several methods for convertingalong to aString and aString to along, as well as other constants and methods useful when dealingwith along.
This is avalue-basedclass; programmers should treat instances that areequal as interchangeable and should notuse instances for synchronization, or unpredictable behavior mayoccur. For example, in a future release, synchronization may fail.
Implementation note: The implementations of the "bit twiddling"methods (such ashighestOneBit andnumberOfTrailingZeros) arebased on material from Henry S. Warren, Jr.'sHacker'sDelight, (Addison Wesley, 2002) andHacker'sDelight, Second Edition, (Pearson Education, 2013).
- Since:
- 1.0
- See Also:
Field Summary
FieldsModifier and TypeFieldDescriptionstatic final intThe number of bytes used to represent alongvalue in two'scomplement binary form.static final longA constant holding the maximum value alongcanhave, 263-1.static final longA constant holding the minimum value alongcanhave, -263.static final intThe number of bits used to represent alongvalue in two'scomplement binary form.TheClassinstance representing the primitive typelong.Constructor Summary
ConstructorsMethod Summary
Modifier and TypeMethodDescriptionstatic intbitCount(long i) Returns the number of one-bits in the two's complement binaryrepresentation of the specifiedlongvalue.byteReturns the value of thisLongas abyteaftera narrowing primitive conversion.static intcompare(long x, long y) Compares twolongvalues numerically.intCompares twoLongobjects numerically.static intcompareUnsigned(long x, long y) Compares twolongvalues numerically treating the valuesas unsigned.static longcompress(long i, long mask) Returns the value obtained by compressing the bits of thespecifiedlongvalue,i, in accordance withthe specified bit mask.staticLongDecodes aStringinto aLong.Returns anOptionalcontaining the nominal descriptor for thisinstance, which is the instance itself.static longdivideUnsigned(long dividend, long divisor) Returns the unsigned quotient of dividing the first argument bythe second where each argument and the result is interpreted asan unsigned value.doubleReturns the value of thisLongas adoubleafter a widening primitive conversion.booleanCompares this object to the specified object.static longexpand(long i, long mask) Returns the value obtained by expanding the bits of thespecifiedlongvalue,i, in accordance withthe specified bit mask.floatReturns the value of thisLongas afloataftera widening primitive conversion.staticLongDetermines thelongvalue of the system propertywith the specified name.staticLongDetermines thelongvalue of the system propertywith the specified name.staticLongReturns thelongvalue of the system property withthe specified name.inthashCode()Returns a hash code for thisLong.static inthashCode(long value) Returns a hash code for alongvalue; compatible withLong.hashCode().static longhighestOneBit(long i) Returns alongvalue with at most a single one-bit, in theposition of the highest-order ("leftmost") one-bit in the specifiedlongvalue.intintValue()Returns the value of thisLongas anintaftera narrowing primitive conversion.longReturns the value of thisLongas alongvalue.static longlowestOneBit(long i) Returns alongvalue with at most a single one-bit, in theposition of the lowest-order ("rightmost") one-bit in the specifiedlongvalue.static longmax(long a, long b) Returns the greater of twolongvaluesas if by callingMath.max.static longmin(long a, long b) Returns the smaller of twolongvaluesas if by callingMath.min.static intnumberOfLeadingZeros(long i) Returns the number of zero bits preceding the highest-order("leftmost") one-bit in the two's complement binary representationof the specifiedlongvalue.static intnumberOfTrailingZeros(long i) Returns the number of zero bits following the lowest-order ("rightmost")one-bit in the two's complement binary representation of the specifiedlongvalue.static longparseLong(CharSequence s, int beginIndex, int endIndex, int radix) Parses theCharSequenceargument as a signedlonginthe specifiedradix, beginning at the specifiedbeginIndexand extending toendIndex - 1.static longParses the string argument as a signed decimallong.static longParses the string argument as a signedlongin theradix specified by the second argument.static longparseUnsignedLong(CharSequence s, int beginIndex, int endIndex, int radix) Parses theCharSequenceargument as an unsignedlonginthe specifiedradix, beginning at the specifiedbeginIndexand extending toendIndex - 1.static longParses the string argument as an unsigned decimallong.static longparseUnsignedLong(String s, int radix) Parses the string argument as an unsignedlongin theradix specified by the second argument.static longremainderUnsigned(long dividend, long divisor) Returns the unsigned remainder from dividing the first argumentby the second where each argument and the result is interpretedas an unsigned value.Resolves this instance as aConstantDesc, the result of which isthe instance itself.static longreverse(long i) Returns the value obtained by reversing the order of the bits in thetwo's complement binary representation of the specifiedlongvalue.static longreverseBytes(long i) Returns the value obtained by reversing the order of the bytes in thetwo's complement representation of the specifiedlongvalue.static longrotateLeft(long i, int distance) Returns the value obtained by rotating the two's complement binaryrepresentation of the specifiedlongvalue left by thespecified number of bits.static longrotateRight(long i, int distance) Returns the value obtained by rotating the two's complement binaryrepresentation of the specifiedlongvalue right by thespecified number of bits.shortReturns the value of thisLongas ashortaftera narrowing primitive conversion.static intsignum(long i) Returns the signum function of the specifiedlongvalue.static longsum(long a, long b) Adds twolongvalues together as per the + operator.staticStringtoBinaryString(long i) Returns a string representation of thelongargument as an unsigned integer in base 2.staticStringtoHexString(long i) Returns a string representation of thelongargument as an unsigned integer in base 16.staticStringtoOctalString(long i) Returns a string representation of thelongargument as an unsigned integer in base 8.toString()Returns aStringobject representing thisLong's value.staticStringtoString(long i) Returns aStringobject representing the specifiedlong.staticStringtoString(long i, int radix) Returns a string representation of the first argument in theradix specified by the second argument.staticStringtoUnsignedString(long i) Returns a string representation of the argument as an unsigneddecimal value.staticStringtoUnsignedString(long i, int radix) Returns a string representation of the first argument as anunsigned integer value in the radix specified by the secondargument.staticLongvalueOf(long l) Returns aLonginstance representing the specifiedlongvalue.staticLongReturns aLongobject holding the valueof the specifiedString.staticLongReturns aLongobject holding the valueextracted from the specifiedStringwhen parsedwith the radix given by the second argument.
Field Details
MIN_VALUE
A constant holding the minimum value alongcanhave, -263.- See Also:
MAX_VALUE
A constant holding the maximum value alongcanhave, 263-1.- See Also:
TYPE
SIZE
The number of bits used to represent alongvalue in two'scomplement binary form.- Since:
- 1.5
- See Also:
BYTES
public static final int BYTESThe number of bytes used to represent alongvalue in two'scomplement binary form.- Since:
- 1.8
- See Also:
Constructor Details
Long
Deprecated.It is rarely appropriate to use this constructor. The static factoryvalueOf(long)is generally a better choice, as it islikely to yield significantly better space and time performance.Constructs a newly allocatedLongobject thatrepresents the specifiedlongargument.- Parameters:
value- the value to be represented by theLongobject.
Long
Deprecated.It is rarely appropriate to use this constructor.UseparseLong(String)to convert a string to alongprimitive, or usevalueOf(String)to convert a string to aLongobject.Constructs a newly allocatedLongobject thatrepresents thelongvalue indicated by theStringparameter. The string is converted to alongvalue in exactly the manner used by theparseLongmethod for radix 10.- Parameters:
s- theStringto be converted to aLong.- Throws:
NumberFormatException- if theStringdoes not contain a parsablelong.
Method Details
toString
Returns a string representation of the first argument in theradix specified by the second argument.If the radix is smaller than
Character.MIN_RADIXor larger thanCharacter.MAX_RADIX, then the radix10is used instead.If the first argument is negative, the first element of theresult is the ASCII minus sign
'-'('\u002d'). If the first argument is notnegative, no sign character appears in the result.The remaining characters of the result represent the magnitudeof the first argument. If the magnitude is zero, it isrepresented by a single zero character
'0'('\u0030'); otherwise, the first character ofthe representation of the magnitude will not be the zerocharacter. The following ASCII characters are used as digits:
These are0123456789abcdefghijklmnopqrstuvwxyz'\u0030'through'\u0039'and'\u0061'through'\u007a'. IfradixisN, then the firstN of these charactersare used as radix-N digits in the order shown. Thus,the digits for hexadecimal (radix 16) are0123456789abcdef. If uppercase letters aredesired, theString.toUpperCase()method maybe called on the result:Long.toString(n, 16).toUpperCase()- Parameters:
i- alongto be converted to a string.radix- the radix to use in the string representation.- Returns:
- a string representation of the argument in the specified radix.
- See Also:
toUnsignedString
Returns a string representation of the first argument as anunsigned integer value in the radix specified by the secondargument.If the radix is smaller than
Character.MIN_RADIXor larger thanCharacter.MAX_RADIX, then the radix10is used instead.Note that since the first argument is treated as an unsignedvalue, no leading sign character is printed.
If the magnitude is zero, it is represented by a single zerocharacter
'0'('\u0030'); otherwise,the first character of the representation of the magnitude willnot be the zero character.The behavior of radixes and the characters used as digitsare the same as
toString.- Parameters:
i- an integer to be converted to an unsigned string.radix- the radix to use in the string representation.- Returns:
- an unsigned string representation of the argument in the specified radix.
- Since:
- 1.8
- See Also:
toHexString
Returns a string representation of thelongargument as an unsigned integer in base 16.The unsigned
longvalue is the argument plus264 if the argument is negative; otherwise, it isequal to the argument. This value is converted to a string ofASCII digits in hexadecimal (base 16) with no extraleading0s.The value of the argument can be recovered from the returnedstring
sby callingLong.parseUnsignedLong(s,16).If the unsigned magnitude is zero, it is represented by asingle zero character
'0'('\u0030');otherwise, the first character of the representation of theunsigned magnitude will not be the zero character. Thefollowing characters are used as hexadecimal digits:
These are the characters0123456789abcdef'\u0030'through'\u0039'and'\u0061'through'\u0066'. If uppercase letters are desired,theString.toUpperCase()method may be calledon the result:Long.toHexString(n).toUpperCase()- API Note:
- The
HexFormatclass provides formatting and parsingof byte arrays and primitives to return a string or adding to anAppendable.HexFormatformats and parses uppercase or lowercase hexadecimal characters,with leading zeros and for byte arrays includes for each bytea delimiter, prefix, and suffix. - Parameters:
i- alongto be converted to a string.- Returns:
- the string representation of the unsigned
longvalue represented by the argument in hexadecimal (base 16). - Since:
- 1.0.2
- See Also:
toOctalString
Returns a string representation of thelongargument as an unsigned integer in base 8.The unsigned
longvalue is the argument plus264 if the argument is negative; otherwise, it isequal to the argument. This value is converted to a string ofASCII digits in octal (base 8) with no extra leading0s.The value of the argument can be recovered from the returnedstring
sby callingLong.parseUnsignedLong(s,8).If the unsigned magnitude is zero, it is represented by asingle zero character
'0'('\u0030');otherwise, the first character of the representation of theunsigned magnitude will not be the zero character. Thefollowing characters are used as octal digits:
These are the characters01234567'\u0030'through'\u0037'.- Parameters:
i- alongto be converted to a string.- Returns:
- the string representation of the unsigned
longvalue represented by the argument in octal (base 8). - Since:
- 1.0.2
- See Also:
toBinaryString
Returns a string representation of thelongargument as an unsigned integer in base 2.The unsigned
longvalue is the argument plus264 if the argument is negative; otherwise, it isequal to the argument. This value is converted to a string ofASCII digits in binary (base 2) with no extra leading0s.The value of the argument can be recovered from the returnedstring
sby callingLong.parseUnsignedLong(s,2).If the unsigned magnitude is zero, it is represented by asingle zero character
'0'('\u0030');otherwise, the first character of the representation of theunsigned magnitude will not be the zero character. Thecharacters'0'('\u0030') and'1'('\u0031') are used as binary digits.- Parameters:
i- alongto be converted to a string.- Returns:
- the string representation of the unsigned
longvalue represented by the argument in binary (base 2). - Since:
- 1.0.2
- See Also:
toString
Returns aStringobject representing the specifiedlong. The argument is converted to signed decimalrepresentation and returned as a string, exactly as if theargument and the radix 10 were given as arguments to thetoString(long, int)method.- Parameters:
i- alongto be converted.- Returns:
- a string representation of the argument in base 10.
toUnsignedString
Returns a string representation of the argument as an unsigneddecimal value.The argument is converted to unsigned decimal representationand returned as a string exactly as if the argument and radix10 were given as arguments to thetoUnsignedString(long, int)method.- Parameters:
i- an integer to be converted to an unsigned string.- Returns:
- an unsigned string representation of the argument.
- Since:
- 1.8
- See Also:
parseLong
Parses the string argument as a signedlongin theradix specified by the second argument. The characters in thestring must all be digits of the specified radix (as determinedby whetherCharacter.digit(char, int)returnsa nonnegative value), except that the first character may be anASCII minus sign'-'('\u002D') toindicate a negative value or an ASCII plus sign'+'('\u002B') to indicate a positive value. Theresultinglongvalue is returned.Note that neither the character
L('\u004C') norl('\u006C') is permitted to appear at the endof the string as a type indicator, as would be permitted inJava programming language source code - except that eitherLorlmay appear as a digit for aradix greater than or equal to 22.An exception of type
NumberFormatExceptionisthrown if any of the following situations occurs:- The first argument is
nullor is a string oflength zero. - The
radixis either smaller thanCharacter.MIN_RADIXor larger thanCharacter.MAX_RADIX. - Any character of the string is not a digit of the specifiedradix, except that the first character may be a minus sign
'-'('\u002d') or plus sign'+'('\u002B') provided that the string islonger than length 1. - The value represented by the string is not a value of type
long.
Examples:
parseLong("0", 10) returns 0LparseLong("473", 10) returns 473LparseLong("+42", 10) returns 42LparseLong("-0", 10) returns 0LparseLong("-FF", 16) returns -255LparseLong("1100110", 2) returns 102LparseLong("99", 8) throws a NumberFormatExceptionparseLong("Hazelnut", 10) throws a NumberFormatExceptionparseLong("Hazelnut", 36) returns 1356099454469L- Parameters:
s- theStringcontaining thelongrepresentation to be parsed.radix- the radix to be used while parsings.- Returns:
- the
longrepresented by the string argument in the specified radix. - Throws:
NumberFormatException- if the string does not contain a parsablelong.
- The first argument is
parseLong
public static long parseLong(CharSequence s, int beginIndex, int endIndex, int radix) throwsNumberFormatException Parses theCharSequenceargument as a signedlonginthe specifiedradix, beginning at the specifiedbeginIndexand extending toendIndex - 1.The method does not take steps to guard against the
CharSequencebeing mutated while parsing.- Parameters:
s- theCharSequencecontaining thelongrepresentation to be parsedbeginIndex- the beginning index, inclusive.endIndex- the ending index, exclusive.radix- the radix to be used while parsings.- Returns:
- the signed
longrepresented by the subsequence in the specified radix. - Throws:
NullPointerException- ifsis null.IndexOutOfBoundsException- ifbeginIndexis negative, or ifbeginIndexis greater thanendIndexor ifendIndexis greater thans.length().NumberFormatException- if theCharSequencedoes not contain a parsablelongin the specifiedradix, or ifradixis either smaller thanCharacter.MIN_RADIXor larger thanCharacter.MAX_RADIX.- Since:
- 9
parseLong
Parses the string argument as a signed decimallong.The characters in the string must all be decimal digits, exceptthat the first character may be an ASCII minus sign'-'(\u002D') to indicate a negative value or anASCII plus sign'+'('\u002B') toindicate a positive value. The resultinglongvalue isreturned, exactly as if the argument and the radix10were given as arguments to theparseLong(java.lang.String, int)method.Note that neither the character
L('\u004C') norl('\u006C') is permitted to appear at the endof the string as a type indicator, as would be permitted inJava programming language source code.- Parameters:
s- aStringcontaining thelongrepresentation to be parsed- Returns:
- the
longrepresented by the argument in decimal. - Throws:
NumberFormatException- if the string does not contain a parsablelong.
parseUnsignedLong
Parses the string argument as an unsignedlongin theradix specified by the second argument. An unsigned integermaps the values usually associated with negative numbers topositive numbers larger thanMAX_VALUE.The characters in the string must all be digits of thespecified radix (as determined by whetherCharacter.digit(char, int)returns a nonnegativevalue), except that the first character may be an ASCII plussign'+'('\u002B'). The resultinginteger value is returned.An exception of type
NumberFormatExceptionisthrown if any of the following situations occurs:- The first argument is
nullor is a string oflength zero. - The radix is either smaller than
Character.MIN_RADIXorlarger thanCharacter.MAX_RADIX. - Any character of the string is not a digit of the specifiedradix, except that the first character may be a plus sign
'+'('\u002B') provided that thestring is longer than length 1. - The value represented by the string is larger than thelargest unsigned
long, 264-1.
- Parameters:
s- theStringcontaining the unsigned integer representation to be parsedradix- the radix to be used while parsings.- Returns:
- the unsigned
longrepresented by the string argument in the specified radix. - Throws:
NumberFormatException- if theStringdoes not contain a parsablelong.- Since:
- 1.8
- The first argument is
parseUnsignedLong
public static long parseUnsignedLong(CharSequence s, int beginIndex, int endIndex, int radix) throwsNumberFormatException Parses theCharSequenceargument as an unsignedlonginthe specifiedradix, beginning at the specifiedbeginIndexand extending toendIndex - 1.The method does not take steps to guard against the
CharSequencebeing mutated while parsing.- Parameters:
s- theCharSequencecontaining the unsignedlongrepresentation to be parsedbeginIndex- the beginning index, inclusive.endIndex- the ending index, exclusive.radix- the radix to be used while parsings.- Returns:
- the unsigned
longrepresented by the subsequence in the specified radix. - Throws:
NullPointerException- ifsis null.IndexOutOfBoundsException- ifbeginIndexis negative, or ifbeginIndexis greater thanendIndexor ifendIndexis greater thans.length().NumberFormatException- if theCharSequencedoes not contain a parsable unsignedlongin the specifiedradix, or ifradixis either smaller thanCharacter.MIN_RADIXor larger thanCharacter.MAX_RADIX.- Since:
- 9
parseUnsignedLong
Parses the string argument as an unsigned decimallong. Thecharacters in the string must all be decimal digits, exceptthat the first character may be an ASCII plus sign'+'('\u002B'). The resulting integer valueis returned, exactly as if the argument and the radix 10 weregiven as arguments to theparseUnsignedLong(java.lang.String, int)method.- Parameters:
s- aStringcontaining the unsignedlongrepresentation to be parsed- Returns:
- the unsigned
longvalue represented by the decimal string argument - Throws:
NumberFormatException- if the string does not contain a parsable unsigned integer.- Since:
- 1.8
valueOf
Returns aLongobject holding the valueextracted from the specifiedStringwhen parsedwith the radix given by the second argument. The firstargument is interpreted as representing a signedlongin the radix specified by the secondargument, exactly as if the arguments were given to theparseLong(java.lang.String, int)method. The result is aLongobject that represents thelongvalue specified by the string.In other words, this method returns a
Longobject equalto the value of:Long.valueOf(Long.parseLong(s, radix))- Parameters:
s- the string to be parsedradix- the radix to be used in interpretings- Returns:
- a
Longobject holding the value represented by the string argument in the specified radix. - Throws:
NumberFormatException- If theStringdoes not contain a parsablelong.
valueOf
Returns aLongobject holding the valueof the specifiedString. The argument isinterpreted as representing a signed decimallong,exactly as if the argument were given to theparseLong(java.lang.String)method. The result is aLongobject that represents the integer valuespecified by the string.In other words, this method returns a
Longobjectequal to the value of:Long.valueOf(Long.parseLong(s))- Parameters:
s- the string to be parsed.- Returns:
- a
Longobject holding the value represented by the string argument. - Throws:
NumberFormatException- If the string cannot be parsed as along.
valueOf
Returns aLonginstance representing the specifiedlongvalue.If a newLonginstance is not required, this methodshould generally be used in preference to the constructorLong(long), as this method is likely to yieldsignificantly better space and time performance by cachingfrequently requested values.This method will always cache values in the range -128 to 127,inclusive, and may cache other values outside of this range.- Parameters:
l- a long value.- Returns:
- a
Longinstance representingl. - Since:
- 1.5
decode
Decodes aStringinto aLong.Accepts decimal, hexadecimal, and octal numbers given by thefollowing grammar:
DecimalNumeral,HexDigits, andOctalDigitsare as defined in section3.10.1 ofThe Java Language Specification,except that underscores are not accepted between digits.- DecodableString:
- Signopt DecimalNumeral
- Signopt
0xHexDigits- Signopt
0XHexDigits- Signopt
#HexDigits- Signopt
0OctalDigits - Signopt
- Sign:
-+
The sequence of characters following an optionalsign and/or radix specifier ("
0x", "0X","#", or leading zero) is parsed as by theLong.parseLongmethod with the indicated radix (10, 16, or 8).This sequence of characters must represent a positive value oraNumberFormatExceptionwill be thrown. The result isnegated if first character of the specifiedStringisthe minus sign. No whitespace characters are permitted in theString.- Parameters:
nm- theStringto decode.- Returns:
- a
Longobject holding thelongvalue represented bynm - Throws:
NumberFormatException- if theStringdoes not contain a parsablelong.- Since:
- 1.2
- See Also:
byteValue
public byte byteValue()Returns the value of thisLongas abyteaftera narrowing primitive conversion.- Overrides:
byteValuein classNumber- Returns:
- the numeric value represented by this object after conversion to type
byte. - SeeJava Language Specification:
- 5.1.3 Narrowing Primitive Conversion
shortValue
public short shortValue()Returns the value of thisLongas ashortaftera narrowing primitive conversion.- Overrides:
shortValuein classNumber- Returns:
- the numeric value represented by this object after conversion to type
short. - SeeJava Language Specification:
- 5.1.3 Narrowing Primitive Conversion
intValue
public int intValue()Returns the value of thisLongas anintaftera narrowing primitive conversion.- Specified by:
intValuein classNumber- Returns:
- the numeric value represented by this object after conversion to type
int. - SeeJava Language Specification:
- 5.1.3 Narrowing Primitive Conversion
longValue
floatValue
public float floatValue()Returns the value of thisLongas afloataftera widening primitive conversion.- Specified by:
floatValuein classNumber- Returns:
- the numeric value represented by this object after conversion to type
float. - SeeJava Language Specification:
- 5.1.2 Widening Primitive Conversion
doubleValue
public double doubleValue()Returns the value of thisLongas adoubleafter a widening primitive conversion.- Specified by:
doubleValuein classNumber- Returns:
- the numeric value represented by this object after conversion to type
double. - SeeJava Language Specification:
- 5.1.2 Widening Primitive Conversion
toString
Returns aStringobject representing thisLong's value. The value is converted to signeddecimal representation and returned as a string, exactly as ifthelongvalue were given as an argument to thetoString(long)method.hashCode
public int hashCode()Returns a hash code for thisLong. The result isthe exclusive OR of the two halves of the primitivelongvalue held by thisLongobject. That is, the hashcode is the value of the expression:(int)(this.longValue()^(this.longValue()>>>32))hashCode
public static int hashCode(long value) Returns a hash code for alongvalue; compatible withLong.hashCode().- Parameters:
value- the value to hash- Returns:
- a hash code value for a
longvalue. - Since:
- 1.8
equals
Compares this object to the specified object. The result istrueif and only if the argument is notnulland is aLongobject thatcontains the samelongvalue as this object.getLong
Determines thelongvalue of the system propertywith the specified name.The first argument is treated as the name of a systemproperty. System properties are accessible through the
System.getProperty(java.lang.String)method. Thestring value of this property is then interpreted as alongvalue using the grammar supported bydecodeand aLongobject representing this value is returned.If there is no property with the specified name, if thespecified name is empty or
null, or if the propertydoes not have the correct numeric format, thennullisreturned.In other words, this method returns a
Longobjectequal to the value of:getLong(nm, null)- Parameters:
nm- property name.- Returns:
- the
Longvalue of the property. - See Also:
getLong
Determines thelongvalue of the system propertywith the specified name.The first argument is treated as the name of a systemproperty. System properties are accessible through the
System.getProperty(java.lang.String)method. Thestring value of this property is then interpreted as alongvalue using the grammar supported bydecodeand aLongobject representing this value is returned.The second argument is the default value. A
Longobjectthat represents the value of the second argument is returned if thereis no property of the specified name, if the property does not havethe correct numeric format, or if the specified name is empty or null.In other words, this method returns a
Longobject equalto the value of:
but in practice it may be implemented in a manner such as:getLong(nm, Long.valueOf(val))
to avoid the unnecessary allocation of aLong result = getLong(nm, null);return (result == null) ? Long.valueOf(val) : result;
Longobject whenthe default value is not needed.- Parameters:
nm- property name.val- default value.- Returns:
- the
Longvalue of the property. - See Also:
getLong
Returns thelongvalue of the system property withthe specified name. The first argument is treated as the nameof a system property. System properties are accessible throughtheSystem.getProperty(java.lang.String)method. The string value of this property is then interpretedas alongvalue, as per thedecodemethod, and aLongobjectrepresenting this value is returned; in summary:- If the property value begins with the two ASCII characters
0xor the ASCII character#, not followed bya minus sign, then the rest of it is parsed as a hexadecimal integerexactly as for the methodvalueOf(java.lang.String, int)with radix 16. - If the property value begins with the ASCII character
0followed by another character, it is parsed asan octal integer exactly as by the methodvalueOf(java.lang.String, int)with radix 8. - Otherwise the property value is parsed as a decimalinteger exactly as by the method
valueOf(java.lang.String, int)with radix 10.
Note that, in every case, neither
L('\u004C') norl('\u006C') is permitted to appear at the endof the property value as a type indicator, as would bepermitted in Java programming language source code.The second argument is the default value. The default value isreturned if there is no property of the specified name, if theproperty does not have the correct numeric format, or if thespecified name is empty or
null.- Parameters:
nm- property name.val- default value.- Returns:
- the
Longvalue of the property. - See Also:
- If the property value begins with the two ASCII characters
compareTo
Compares twoLongobjects numerically.- Specified by:
compareToin interfaceComparable<Long>- Parameters:
anotherLong- theLongto be compared.- Returns:
- the value
0if thisLongis equal to the argumentLong; a value less than0if thisLongis numerically less than the argumentLong; and a value greater than0if thisLongis numerically greater than the argumentLong(signed comparison). - Since:
- 1.2
compare
public static int compare(long x, long y) Compares twolongvalues numerically.The value returned is identical to what would be returned by:Long.valueOf(x).compareTo(Long.valueOf(y))
- Parameters:
x- the firstlongto comparey- the secondlongto compare- Returns:
- the value
0ifx == y; a value less than0ifx < y; and a value greater than0ifx > y - Since:
- 1.7
compareUnsigned
public static int compareUnsigned(long x, long y) Compares twolongvalues numerically treating the valuesas unsigned.- Parameters:
x- the firstlongto comparey- the secondlongto compare- Returns:
- the value
0ifx == y; a value less than0ifx < yas unsigned values; and a value greater than0ifx > yas unsigned values - Since:
- 1.8
divideUnsigned
public static long divideUnsigned(long dividend, long divisor) Returns the unsigned quotient of dividing the first argument bythe second where each argument and the result is interpreted asan unsigned value.Note that in two's complement arithmetic, the three otherbasic arithmetic operations of add, subtract, and multiply arebit-wise identical if the two operands are regarded as bothbeing signed or both being unsigned. Therefore separate
addUnsigned, etc. methods are not provided.- Parameters:
dividend- the value to be divideddivisor- the value doing the dividing- Returns:
- the unsigned quotient of the first argument divided bythe second argument
- Since:
- 1.8
- See Also:
remainderUnsigned
public static long remainderUnsigned(long dividend, long divisor) Returns the unsigned remainder from dividing the first argumentby the second where each argument and the result is interpretedas an unsigned value.- Parameters:
dividend- the value to be divideddivisor- the value doing the dividing- Returns:
- the unsigned remainder of the first argument divided bythe second argument
- Since:
- 1.8
- See Also:
highestOneBit
public static long highestOneBit(long i) Returns alongvalue with at most a single one-bit, in theposition of the highest-order ("leftmost") one-bit in the specifiedlongvalue. Returns zero if the specified value has noone-bits in its two's complement binary representation, that is, if itis equal to zero.- Parameters:
i- the value whose highest one bit is to be computed- Returns:
- a
longvalue with a single one-bit, in the position of the highest-order one-bit in the specified value, or zero if the specified value is itself equal to zero. - Since:
- 1.5
lowestOneBit
public static long lowestOneBit(long i) Returns alongvalue with at most a single one-bit, in theposition of the lowest-order ("rightmost") one-bit in the specifiedlongvalue. Returns zero if the specified value has noone-bits in its two's complement binary representation, that is, if itis equal to zero.- Parameters:
i- the value whose lowest one bit is to be computed- Returns:
- a
longvalue with a single one-bit, in the position of the lowest-order one-bit in the specified value, or zero if the specified value is itself equal to zero. - Since:
- 1.5
numberOfLeadingZeros
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 representationof the specifiedlongvalue. Returns 64 if thespecified 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
longvalues x:- floor(log2(x)) =
63 - numberOfLeadingZeros(x) - ceil(log2(x)) =
64 - numberOfLeadingZeros(x - 1)
- Parameters:
i- the value whose number of leading zeros is to be computed- Returns:
- the number of zero bits preceding the highest-order ("leftmost") one-bit in the two's complement binary representation of the specified
longvalue, or 64 if the value is equal to zero. - Since:
- 1.5
- floor(log2(x)) =
numberOfTrailingZeros
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 specifiedlongvalue. Returns 64 if the specified value has noone-bits in its two's complement representation, in other words if it isequal to zero.- Parameters:
i- the value whose number of trailing zeros is to be computed- Returns:
- the number of zero bits following the lowest-order ("rightmost") one-bit in the two's complement binary representation of the specified
longvalue, or 64 if the value is equal to zero. - Since:
- 1.5
bitCount
public static int bitCount(long i) Returns the number of one-bits in the two's complement binaryrepresentation of the specifiedlongvalue. This function issometimes referred to as thepopulation count.- Parameters:
i- the value whose bits are to be counted- Returns:
- the number of one-bits in the two's complement binary representation of the specified
longvalue. - Since:
- 1.5
rotateLeft
public static long rotateLeft(long i, int distance) Returns the value obtained by rotating the two's complement binaryrepresentation of the specifiedlongvalue left by thespecified number of bits. (Bits shifted out of the left hand, orhigh-order, side reenter on the right, or low-order.)Note that left rotation with a negative distance is equivalent toright rotation:
rotateLeft(val, -distance) == rotateRight(val,distance). Note also that rotation by any multiple of 64 is ano-op, so all but the last six bits of the rotation distance can beignored, even if the distance is negative:rotateLeft(val,distance) == rotateLeft(val, distance & 0x3F).- Parameters:
i- the value whose bits are to be rotated leftdistance- the number of bit positions to rotate left- Returns:
- the value obtained by rotating the two's complement binary representation of the specified
longvalue left by the specified number of bits. - Since:
- 1.5
rotateRight
public static long rotateRight(long i, int distance) Returns the value obtained by rotating the two's complement binaryrepresentation of the specifiedlongvalue right by thespecified number of bits. (Bits shifted out of the right hand, orlow-order, side reenter on the left, or high-order.)Note that right rotation with a negative distance is equivalent toleft rotation:
rotateRight(val, -distance) == rotateLeft(val,distance). Note also that rotation by any multiple of 64 is ano-op, so all but the last six bits of the rotation distance can beignored, even if the distance is negative:rotateRight(val,distance) == rotateRight(val, distance & 0x3F).- Parameters:
i- the value whose bits are to be rotated rightdistance- the number of bit positions to rotate right- Returns:
- the value obtained by rotating the two's complement binary representation of the specified
longvalue right by the specified number of bits. - Since:
- 1.5
reverse
public static long reverse(long i) Returns the value obtained by reversing the order of the bits in thetwo's complement binary representation of the specifiedlongvalue.- Parameters:
i- the value to be reversed- Returns:
- the value obtained by reversing order of the bits in the specified
longvalue. - Since:
- 1.5
compress
public static long compress(long i, long mask) Returns the value obtained by compressing the bits of thespecifiedlongvalue,i, in accordance withthe specified bit mask.For each one-bit value
mbof the mask, from leastsignificant to most significant, the bit value ofiatthe same bit location asmbis assigned to the compressedvalue contiguously starting from the least significant bit location.All the upper remaining bits of the compressed value are setto zero.- API Note:
- Consider the simple case of compressing the digits of a hexadecimalvalue:Starting from the least significant hexadecimal digit at position 0from the right, the mask
// Compressing drink to foodcompress(0xCAFEBABEL, 0xFF00FFF0L) == 0xCABABL0xFF00FFF0selects hexadecimal digitsat positions 1, 2, 3, 6 and 7 of0xCAFEBABE. The selected digitsoccur in the resulting compressed value contiguously from digit position0 in the same order.The following identities all return
trueand are helpful tounderstand the behaviour ofcompress:// Returns 1 if the bit at position n is onecompress(x, 1L << n) == (x >> n & 1)// Logical shift rightcompress(x, -1L << n) == x >>> n// Any bits not covered by the mask are ignoredcompress(x, m) == compress(x & m, m)// Compressing a value by itselfcompress(m, m) == (m == -1 || m == 0) ? m : (1L << bitCount(m)) - 1// Expanding then compressing with the same maskcompress(expand(x, m), m) == x & compress(m, m)The Sheep And Goats (SAG) operation (see Hacker's Delight, Second Edition, 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 goatssag(0x00000000_CAFEBABEL, 0xFFFFFFFF_FF00FFF0L) == 0x00000000_CABABFEEL - Parameters:
i- the value whose bits are to be compressedmask- the bit mask- Returns:
- the compressed value
- Since:
- 19
- See Also:
expand
public static long expand(long i, long mask) Returns the value obtained by expanding the bits of thespecifiedlongvalue,i, in accordance withthe specified bit mask.For each one-bit value
mbof the mask, from leastsignificant to most significant, the next contiguous bit valueofistarting at the least significant bit is assignedto the expanded value at the same bit location asmb.All other remaining bits of the expanded value are set to zero.- API Note:
- Consider the simple case of expanding the digits of a hexadecimalvalue:Starting from the least significant hexadecimal digit at position 0from the right, the mask
expand(0x0000CABABL, 0xFF00FFF0L) == 0xCA00BAB0L0xFF00FFF0selects the first fivehexadecimal digits of0x0000CABAB. The selected digits occurin the resulting expanded value in order at positions 1, 2, 3, 6, and 7.The following identities all return
trueand are helpful tounderstand the behaviour ofexpand:// Logically shift right the bit at position 0expand(x, 1L << n) == (x & 1) << n// Logically shift rightexpand(x, -1L << n) == x << n// Expanding all bits returns the maskexpand(-1L, m) == m// Any bits not covered by the mask are ignoredexpand(x, m) == expand(x, m) & m// Compressing then expanding with the same maskexpand(compress(x, m), m) == x & mThe select operation for determining the position of the one-bit withindex
nin alongvalue 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 1select(0b10101010_10101010, 0) == 1// The one-bit with index 3 is at bit position 7select(0b10101010_10101010, 3) == 7 - Parameters:
i- the value whose bits are to be expandedmask- the bit mask- Returns:
- the expanded value
- Since:
- 19
- See Also:
signum
public static int signum(long i) Returns the signum function of the specifiedlongvalue. (Thereturn value is -1 if the specified value is negative; 0 if thespecified value is zero; and 1 if the specified value is positive.)- Parameters:
i- the value whose signum is to be computed- Returns:
- the signum function of the specified
longvalue. - Since:
- 1.5
reverseBytes
public static long reverseBytes(long i) Returns the value obtained by reversing the order of the bytes in thetwo's complement representation of the specifiedlongvalue.- Parameters:
i- the value whose bytes are to be reversed- Returns:
- the value obtained by reversing the bytes in the specified
longvalue. - Since:
- 1.5
sum
public static long sum(long a, long b) Adds twolongvalues together as per the + operator.- Parameters:
a- the first operandb- the second operand- Returns:
- the sum of
aandb - Since:
- 1.8
- See Also:
max
public static long max(long a, long b) Returns the greater of twolongvaluesas if by callingMath.max.- Parameters:
a- the first operandb- the second operand- Returns:
- the greater of
aandb - Since:
- 1.8
- See Also:
min
public static long min(long a, long b) Returns the smaller of twolongvaluesas if by callingMath.min.- Parameters:
a- the first operandb- the second operand- Returns:
- the smaller of
aandb - Since:
- 1.8
- See Also:
describeConstable
resolveConstantDesc
Resolves this instance as aConstantDesc, the result of which isthe instance itself.- Specified by:
resolveConstantDescin interfaceConstantDesc- Parameters:
lookup- ignored- Returns:
- theLong instance
- Since:
- 12