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java.lang.Objectcom.google.common.math.LongMath
@Beta public final class LongMath
A class for arithmetic on values of type long. Where possible, methods are defined and
named analogously to their BigInteger counterparts.
The implementations of many methods in this class are based on material from Henry S. Warren, Jr.'s Hacker's Delight, (Addison Wesley, 2002).
Similar functionality for int and for BigInteger can be found in
IntMath and BigIntegerMath respectively. For other common operations on
long values, see Longs.
| Method Summary | |
|---|---|
static long |
binomial(int n,
int k)
Returns n choose k, also known as the binomial coefficient of n and
k, or Long.MAX_VALUE if the result does not fit in a long. |
static long |
checkedAdd(long a,
long b)
Returns the sum of a and b, provided it does not overflow. |
static long |
checkedMultiply(long a,
long b)
Returns the product of a and b, provided it does not overflow. |
static long |
checkedPow(long b,
int k)
Returns the b to the kth power, provided it does not overflow. |
static long |
checkedSubtract(long a,
long b)
Returns the difference of a and b, provided it does not overflow. |
static long |
divide(long p,
long q,
RoundingMode mode)
Returns the result of dividing p by q, rounding using the specified
RoundingMode. |
static long |
factorial(int n)
Returns n!, that is, the product of the first n positive
integers, 1 if n == 0, or Long.MAX_VALUE if the
result does not fit in a long. |
static long |
gcd(long a,
long b)
Returns the greatest common divisor of a, b. |
static boolean |
isPowerOfTwo(long x)
Returns true if x represents a power of two. |
static int |
log10(long x,
RoundingMode mode)
Returns the base-10 logarithm of x, rounded according to the specified rounding mode. |
static int |
log2(long x,
RoundingMode mode)
Returns the base-2 logarithm of x, rounded according to the specified rounding mode. |
static int |
mod(long x,
int m)
Returns x mod m. |
static long |
mod(long x,
long m)
Returns x mod m. |
static long |
pow(long b,
int k)
Returns b to the kth power. |
static long |
sqrt(long x,
RoundingMode mode)
Returns the square root of x, rounded with the specified rounding mode. |
| Methods inherited from class java.lang.Object |
|---|
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
| Method Detail |
|---|
public static boolean isPowerOfTwo(long x)
true if x represents a power of two.
This differs from Long.bitCount(x) == 1, because
Long.bitCount(Long.MIN_VALUE) == 1, but Long.MIN_VALUE is not a power of two.
public static int log2(long x,
RoundingMode mode)
x, rounded according to the specified rounding mode.
IllegalArgumentException - if x <= 0
ArithmeticException - if mode is RoundingMode.UNNECESSARY and x
is not a power of two
public static int log10(long x,
RoundingMode mode)
x, rounded according to the specified rounding mode.
IllegalArgumentException - if x <= 0
ArithmeticException - if mode is RoundingMode.UNNECESSARY and x
is not a power of ten
public static long pow(long b,
int k)
b to the kth power. Even if the result overflows, it will be equal to
BigInteger.valueOf(b).pow(k).longValue(). This implementation runs in O(log k)
time.
IllegalArgumentException - if k < 0
public static long sqrt(long x,
RoundingMode mode)
x, rounded with the specified rounding mode.
IllegalArgumentException - if x < 0
ArithmeticException - if mode is RoundingMode.UNNECESSARY and
sqrt(x) is not an integer
public static long divide(long p,
long q,
RoundingMode mode)
p by q, rounding using the specified
RoundingMode.
ArithmeticException - if q == 0, or if mode == UNNECESSARY and a
is not an integer multiple of b
public static int mod(long x,
int m)
x mod m. This differs from x % m in that it always returns a
non-negative result.
For example:
mod(7, 4) == 3
mod(-7, 4) == 1
mod(-1, 4) == 3
mod(-8, 4) == 0
mod(8, 4) == 0
ArithmeticException - if m <= 0
public static long mod(long x,
long m)
x mod m. This differs from x % m in that it always returns a
non-negative result.
For example:
mod(7, 4) == 3
mod(-7, 4) == 1
mod(-1, 4) == 3
mod(-8, 4) == 0
mod(8, 4) == 0
ArithmeticException - if m <= 0
public static long gcd(long a,
long b)
a, b. Returns 0 if
a == 0 && b == 0.
IllegalArgumentException - if a < 0 or b < 0
public static long checkedAdd(long a,
long b)
a and b, provided it does not overflow.
ArithmeticException - if a + b overflows in signed long arithmetic
public static long checkedSubtract(long a,
long b)
a and b, provided it does not overflow.
ArithmeticException - if a - b overflows in signed long arithmetic
public static long checkedMultiply(long a,
long b)
a and b, provided it does not overflow.
ArithmeticException - if a * b overflows in signed long arithmetic
public static long checkedPow(long b,
int k)
b to the kth power, provided it does not overflow.
ArithmeticException - if b to the kth power overflows in signed
long arithmeticpublic static long factorial(int n)
n!, that is, the product of the first n positive
integers, 1 if n == 0, or Long.MAX_VALUE if the
result does not fit in a long.
IllegalArgumentException - if n < 0
public static long binomial(int n,
int k)
n choose k, also known as the binomial coefficient of n and
k, or Long.MAX_VALUE if the result does not fit in a long.
IllegalArgumentException - if n < 0, k < 0, or k > n
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