Class Longs
- java.lang.Object
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- com.google.common.primitives.Longs
-
@GwtCompatible public final class Longs extends java.lang.Object
Static utility methods pertaining tolong
primitives, that are not already found in eitherLong
orArrays
.See the Guava User Guide article on primitive utilities.
- Since:
- 1.0
- Author:
- Kevin Bourrillion
-
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Field Summary
Fields Modifier and Type Field Description static int
BYTES
The number of bytes required to represent a primitivelong
value.static long
MAX_POWER_OF_TWO
The largest power of two that can be represented as along
.
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Method Summary
All Methods Static Methods Concrete Methods Modifier and Type Method Description static java.util.List<java.lang.Long>
asList(long... backingArray)
Returns a fixed-size list backed by the specified array, similar toArrays.asList(Object[])
.static int
compare(long a, long b)
Compares the two specifiedlong
values.static long[]
concat(long[]... arrays)
Returns the values from each provided array combined into a single array.static long
constrainToRange(long value, long min, long max)
Returns the value nearest tovalue
which is within the closed range[min..max]
.static boolean
contains(long[] array, long target)
Returnstrue
iftarget
is present as an element anywhere inarray
.static long[]
ensureCapacity(long[] array, int minLength, int padding)
Returns an array containing the same values asarray
, but guaranteed to be of a specified minimum length.static long
fromByteArray(byte[] bytes)
Returns thelong
value whose big-endian representation is stored in the first 8 bytes ofbytes
; equivalent toByteBuffer.wrap(bytes).getLong()
.static long
fromBytes(byte b1, byte b2, byte b3, byte b4, byte b5, byte b6, byte b7, byte b8)
Returns thelong
value whose byte representation is the given 8 bytes, in big-endian order; equivalent toLongs.fromByteArray(new byte[] {b1, b2, b3, b4, b5, b6, b7, b8})
.static int
hashCode(long value)
Returns a hash code forvalue
; equal to the result of invoking((Long) value).hashCode()
.static int
indexOf(long[] array, long target)
Returns the index of the first appearance of the valuetarget
inarray
.static int
indexOf(long[] array, long[] target)
Returns the start position of the first occurrence of the specifiedtarget
withinarray
, or-1
if there is no such occurrence.static java.lang.String
join(java.lang.String separator, long... array)
Returns a string containing the suppliedlong
values separated byseparator
.static int
lastIndexOf(long[] array, long target)
Returns the index of the last appearance of the valuetarget
inarray
.static java.util.Comparator<long[]>
lexicographicalComparator()
Returns a comparator that compares twolong
arrays lexicographically.static long
max(long... array)
Returns the greatest value present inarray
.static long
min(long... array)
Returns the least value present inarray
.static void
reverse(long[] array)
Reverses the elements ofarray
.static void
reverse(long[] array, int fromIndex, int toIndex)
Reverses the elements ofarray
betweenfromIndex
inclusive andtoIndex
exclusive.static void
rotate(long[] array, int distance)
Performs a right rotation ofarray
of "distance" places, so that the first element is moved to index "distance", and the element at indexi
ends up at index(distance + i) mod array.length
.static void
rotate(long[] array, int distance, int fromIndex, int toIndex)
Performs a right rotation ofarray
betweenfromIndex
inclusive andtoIndex
exclusive.static void
sortDescending(long[] array)
Sorts the elements ofarray
in descending order.static void
sortDescending(long[] array, int fromIndex, int toIndex)
Sorts the elements ofarray
betweenfromIndex
inclusive andtoIndex
exclusive in descending order.static Converter<java.lang.String,java.lang.Long>
stringConverter()
Returns a serializable converter object that converts between strings and longs usingLong.decode(java.lang.String)
andLong.toString()
.static long[]
toArray(java.util.Collection<? extends java.lang.Number> collection)
Returns an array containing each value ofcollection
, converted to along
value in the manner ofNumber.longValue()
.static byte[]
toByteArray(long value)
Returns a big-endian representation ofvalue
in an 8-element byte array; equivalent toByteBuffer.allocate(8).putLong(value).array()
.static java.lang.Long
tryParse(java.lang.String string)
Parses the specified string as a signed decimal long value.static java.lang.Long
tryParse(java.lang.String string, int radix)
Parses the specified string as a signed long value using the specified radix.
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Field Detail
-
BYTES
public static final int BYTES
The number of bytes required to represent a primitivelong
value.Java 8 users: use
Long.BYTES
instead.- See Also:
- Constant Field Values
-
MAX_POWER_OF_TWO
public static final long MAX_POWER_OF_TWO
The largest power of two that can be represented as along
.- Since:
- 10.0
- See Also:
- Constant Field Values
-
-
Method Detail
-
hashCode
public static int hashCode(long value)
Returns a hash code forvalue
; equal to the result of invoking((Long) value).hashCode()
.This method always return the value specified by
Long.hashCode()
in java, which might be different from((Long) value).hashCode()
in GWT becauseLong.hashCode()
in GWT does not obey the JRE contract.Java 8 users: use
Long.hashCode(long)
instead.- Parameters:
value
- a primitivelong
value- Returns:
- a hash code for the value
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compare
public static int compare(long a, long b)
Compares the two specifiedlong
values. The sign of the value returned is the same as that of((Long) a).compareTo(b)
.Note for Java 7 and later: this method should be treated as deprecated; use the equivalent
Long.compare(long, long)
method instead.- Parameters:
a
- the firstlong
to compareb
- the secondlong
to compare- Returns:
- a negative value if
a
is less thanb
; a positive value ifa
is greater thanb
; or zero if they are equal
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contains
public static boolean contains(long[] array, long target)
Returnstrue
iftarget
is present as an element anywhere inarray
.- Parameters:
array
- an array oflong
values, possibly emptytarget
- a primitivelong
value- Returns:
true
ifarray[i] == target
for some value ofi
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indexOf
public static int indexOf(long[] array, long target)
Returns the index of the first appearance of the valuetarget
inarray
.- Parameters:
array
- an array oflong
values, possibly emptytarget
- a primitivelong
value- Returns:
- the least index
i
for whicharray[i] == target
, or-1
if no such index exists.
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indexOf
public static int indexOf(long[] array, long[] target)
Returns the start position of the first occurrence of the specifiedtarget
withinarray
, or-1
if there is no such occurrence.More formally, returns the lowest index
i
such thatArrays.copyOfRange(array, i, i + target.length)
contains exactly the same elements astarget
.- Parameters:
array
- the array to search for the sequencetarget
target
- the array to search for as a sub-sequence ofarray
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lastIndexOf
public static int lastIndexOf(long[] array, long target)
Returns the index of the last appearance of the valuetarget
inarray
.- Parameters:
array
- an array oflong
values, possibly emptytarget
- a primitivelong
value- Returns:
- the greatest index
i
for whicharray[i] == target
, or-1
if no such index exists.
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min
public static long min(long... array)
Returns the least value present inarray
.- Parameters:
array
- a nonempty array oflong
values- Returns:
- the value present in
array
that is less than or equal to every other value in the array - Throws:
java.lang.IllegalArgumentException
- ifarray
is empty
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max
public static long max(long... array)
Returns the greatest value present inarray
.- Parameters:
array
- a nonempty array oflong
values- Returns:
- the value present in
array
that is greater than or equal to every other value in the array - Throws:
java.lang.IllegalArgumentException
- ifarray
is empty
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constrainToRange
public static long constrainToRange(long value, long min, long max)
Returns the value nearest tovalue
which is within the closed range[min..max]
.If
value
is within the range[min..max]
,value
is returned unchanged. Ifvalue
is less thanmin
,min
is returned, and ifvalue
is greater thanmax
,max
is returned.- Parameters:
value
- thelong
value to constrainmin
- the lower bound (inclusive) of the range to constrainvalue
tomax
- the upper bound (inclusive) of the range to constrainvalue
to- Throws:
java.lang.IllegalArgumentException
- ifmin > max
- Since:
- 21.0
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concat
public static long[] concat(long[]... arrays)
Returns the values from each provided array combined into a single array. For example,concat(new long[] {a, b}, new long[] {}, new long[] {c}
returns the array{a, b, c}
.- Parameters:
arrays
- zero or morelong
arrays- Returns:
- a single array containing all the values from the source arrays, in order
- Throws:
java.lang.IllegalArgumentException
- if the total number of elements inarrays
does not fit in anint
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toByteArray
public static byte[] toByteArray(long value)
Returns a big-endian representation ofvalue
in an 8-element byte array; equivalent toByteBuffer.allocate(8).putLong(value).array()
. For example, the input value0x1213141516171819L
would yield the byte array{0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19}
.If you need to convert and concatenate several values (possibly even of different types), use a shared
ByteBuffer
instance, or useByteStreams.newDataOutput()
to get a growable buffer.
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fromByteArray
public static long fromByteArray(byte[] bytes)
Returns thelong
value whose big-endian representation is stored in the first 8 bytes ofbytes
; equivalent toByteBuffer.wrap(bytes).getLong()
. For example, the input byte array{0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19}
would yield thelong
value0x1213141516171819L
.Arguably, it's preferable to use
ByteBuffer
; that library exposes much more flexibility at little cost in readability.- Throws:
java.lang.IllegalArgumentException
- ifbytes
has fewer than 8 elements
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fromBytes
public static long fromBytes(byte b1, byte b2, byte b3, byte b4, byte b5, byte b6, byte b7, byte b8)
Returns thelong
value whose byte representation is the given 8 bytes, in big-endian order; equivalent toLongs.fromByteArray(new byte[] {b1, b2, b3, b4, b5, b6, b7, b8})
.- Since:
- 7.0
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tryParse
@CheckForNull public static java.lang.Long tryParse(java.lang.String string)
Parses the specified string as a signed decimal long value. The ASCII character'-'
('\u002D'
) is recognized as the minus sign.Unlike
Long.parseLong(String)
, this method returnsnull
instead of throwing an exception if parsing fails. Additionally, this method only accepts ASCII digits, and returnsnull
if non-ASCII digits are present in the string.Note that strings prefixed with ASCII
'+'
are rejected, even under JDK 7, despite the change toLong.parseLong(String)
for that version.- Parameters:
string
- the string representation of a long value- Returns:
- the long value represented by
string
, ornull
ifstring
has a length of zero or cannot be parsed as a long value - Throws:
java.lang.NullPointerException
- ifstring
isnull
- Since:
- 14.0
-
tryParse
@CheckForNull public static java.lang.Long tryParse(java.lang.String string, int radix)
Parses the specified string as a signed long value using the specified radix. The ASCII character'-'
('\u002D'
) is recognized as the minus sign.Unlike
Long.parseLong(String, int)
, this method returnsnull
instead of throwing an exception if parsing fails. Additionally, this method only accepts ASCII digits, and returnsnull
if non-ASCII digits are present in the string.Note that strings prefixed with ASCII
'+'
are rejected, even under JDK 7, despite the change toLong.parseLong(String, int)
for that version.- Parameters:
string
- the string representation of a long valueradix
- the radix to use when parsing- Returns:
- the long value represented by
string
usingradix
, ornull
ifstring
has a length of zero or cannot be parsed as a long value - Throws:
java.lang.IllegalArgumentException
- ifradix < Character.MIN_RADIX
orradix > Character.MAX_RADIX
java.lang.NullPointerException
- ifstring
isnull
- Since:
- 19.0
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stringConverter
public static Converter<java.lang.String,java.lang.Long> stringConverter()
Returns a serializable converter object that converts between strings and longs usingLong.decode(java.lang.String)
andLong.toString()
. The returned converter throwsNumberFormatException
if the input string is invalid.Warning: please see
Long.decode(java.lang.String)
to understand exactly how strings are parsed. For example, the string"0123"
is treated as octal and converted to the value83L
.- Since:
- 16.0
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ensureCapacity
public static long[] ensureCapacity(long[] array, int minLength, int padding)
Returns an array containing the same values asarray
, but guaranteed to be of a specified minimum length. Ifarray
already has a length of at leastminLength
, it is returned directly. Otherwise, a new array of sizeminLength + padding
is returned, containing the values ofarray
, and zeroes in the remaining places.- Parameters:
array
- the source arrayminLength
- the minimum length the returned array must guaranteepadding
- an extra amount to "grow" the array by if growth is necessary- Returns:
- an array containing the values of
array
, with guaranteed minimum lengthminLength
- Throws:
java.lang.IllegalArgumentException
- ifminLength
orpadding
is negative
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join
public static java.lang.String join(java.lang.String separator, long... array)
Returns a string containing the suppliedlong
values separated byseparator
. For example,join("-", 1L, 2L, 3L)
returns the string"1-2-3"
.- Parameters:
separator
- the text that should appear between consecutive values in the resulting string (but not at the start or end)array
- an array oflong
values, possibly empty
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lexicographicalComparator
public static java.util.Comparator<long[]> lexicographicalComparator()
Returns a comparator that compares twolong
arrays lexicographically. That is, it compares, usingcompare(long, long)
), the first pair of values that follow any common prefix, or when one array is a prefix of the other, treats the shorter array as the lesser. For example,[] < [1L] < [1L, 2L] < [2L]
.The returned comparator is inconsistent with
Object.equals(Object)
(since arrays support only identity equality), but it is consistent withArrays.equals(long[], long[])
.- Since:
- 2.0
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sortDescending
public static void sortDescending(long[] array)
Sorts the elements ofarray
in descending order.- Since:
- 23.1
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sortDescending
public static void sortDescending(long[] array, int fromIndex, int toIndex)
Sorts the elements ofarray
betweenfromIndex
inclusive andtoIndex
exclusive in descending order.- Since:
- 23.1
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reverse
public static void reverse(long[] array)
Reverses the elements ofarray
. This is equivalent toCollections.reverse(Longs.asList(array))
, but is likely to be more efficient.- Since:
- 23.1
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reverse
public static void reverse(long[] array, int fromIndex, int toIndex)
Reverses the elements ofarray
betweenfromIndex
inclusive andtoIndex
exclusive. This is equivalent toCollections.reverse(Longs.asList(array).subList(fromIndex, toIndex))
, but is likely to be more efficient.- Throws:
java.lang.IndexOutOfBoundsException
- iffromIndex < 0
,toIndex > array.length
, ortoIndex > fromIndex
- Since:
- 23.1
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rotate
public static void rotate(long[] array, int distance)
Performs a right rotation ofarray
of "distance" places, so that the first element is moved to index "distance", and the element at indexi
ends up at index(distance + i) mod array.length
. This is equivalent toCollections.rotate(Longs.asList(array), distance)
, but is considerably faster and avoids allocation and garbage collection.The provided "distance" may be negative, which will rotate left.
- Since:
- 32.0.0
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rotate
public static void rotate(long[] array, int distance, int fromIndex, int toIndex)
Performs a right rotation ofarray
betweenfromIndex
inclusive andtoIndex
exclusive. This is equivalent toCollections.rotate(Longs.asList(array).subList(fromIndex, toIndex), distance)
, but is considerably faster and avoids allocations and garbage collection.The provided "distance" may be negative, which will rotate left.
- Throws:
java.lang.IndexOutOfBoundsException
- iffromIndex < 0
,toIndex > array.length
, ortoIndex > fromIndex
- Since:
- 32.0.0
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toArray
public static long[] toArray(java.util.Collection<? extends java.lang.Number> collection)
Returns an array containing each value ofcollection
, converted to along
value in the manner ofNumber.longValue()
.Elements are copied from the argument collection as if by
collection.toArray()
. Calling this method is as thread-safe as calling that method.- Parameters:
collection
- a collection ofNumber
instances- Returns:
- an array containing the same values as
collection
, in the same order, converted to primitives - Throws:
java.lang.NullPointerException
- ifcollection
or any of its elements is null- Since:
- 1.0 (parameter was
Collection<Long>
before 12.0)
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asList
public static java.util.List<java.lang.Long> asList(long... backingArray)
Returns a fixed-size list backed by the specified array, similar toArrays.asList(Object[])
. The list supportsList.set(int, Object)
, but any attempt to set a value tonull
will result in aNullPointerException
.The returned list maintains the values, but not the identities, of
Long
objects written to or read from it. For example, whetherlist.get(0) == list.get(0)
is true for the returned list is unspecified.The returned list is serializable.
Note: when possible, you should represent your data as an
ImmutableLongArray
instead, which has anasList
view.- Parameters:
backingArray
- the array to back the list- Returns:
- a list view of the array
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