com.google.common.math
Class LongMath

java.lang.Object
  com.google.common.math.LongMath

@Beta
public final class LongMath
extends Object

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.

Since:

11.0

Author:

Louis Wasserman

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

isPowerOfTwo

public static boolean isPowerOfTwo(long x)

Returns 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.

log2

public static int log2(long x,
                       RoundingMode mode)

Returns the base-2 logarithm of x, rounded according to the specified rounding mode.

Throws:

IllegalArgumentException - if x <= 0

ArithmeticException - if mode is RoundingMode.UNNECESSARY and x is not a power of two

log10

public static int log10(long x,
                        RoundingMode mode)

Returns the base-10 logarithm of x, rounded according to the specified rounding mode.

Throws:

IllegalArgumentException - if x <= 0

ArithmeticException - if mode is RoundingMode.UNNECESSARY and x is not a power of ten

pow

public static long pow(long b,
                       int k)

Returns 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.

Throws:

IllegalArgumentException - if k < 0

sqrt

public static long sqrt(long x,
                        RoundingMode mode)

Returns the square root of x, rounded with the specified rounding mode.

Throws:

IllegalArgumentException - if x < 0

ArithmeticException - if mode is RoundingMode.UNNECESSARY and sqrt(x) is not an integer

divide

public static long divide(long p,
                          long q,
                          RoundingMode mode)

Returns the result of dividing p by q, rounding using the specified RoundingMode.

Throws:

ArithmeticException - if q == 0, or if mode == UNNECESSARY and a is not an integer multiple of b

mod

public static int mod(long x,
                      int m)

Returns 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

Throws:

ArithmeticException - if m <= 0

mod

public static long mod(long x,
                       long m)

Returns 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

Throws:

ArithmeticException - if m <= 0

gcd

public static long gcd(long a,
                       long b)

Returns the greatest common divisor of a, b. Returns 0 if a == 0 && b == 0.

Throws:

IllegalArgumentException - if a < 0 or b < 0

checkedAdd

public static long checkedAdd(long a,
                              long b)

Returns the sum of a and b, provided it does not overflow.

Throws:

ArithmeticException - if a + b overflows in signed long arithmetic

checkedSubtract

public static long checkedSubtract(long a,
                                   long b)

Returns the difference of a and b, provided it does not overflow.

Throws:

ArithmeticException - if a - b overflows in signed long arithmetic

checkedMultiply

public static long checkedMultiply(long a,
                                   long b)

Returns the product of a and b, provided it does not overflow.

Throws:

ArithmeticException - if a * b overflows in signed long arithmetic

checkedPow

public static long checkedPow(long b,
                              int k)

Returns the b to the kth power, provided it does not overflow.

Throws:

ArithmeticException - if b to the kth power overflows in signed long arithmetic

factorial

public 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.

Throws:

IllegalArgumentException - if n < 0

binomial

public 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.

Throws:

IllegalArgumentException - if n < 0, k < 0, or k > n