com.google.common.math
Class IntMath

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

@Beta
@GwtCompatible(emulated=true)
public final class IntMath
extends Object

A class for arithmetic on values of type int. 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 long and for BigInteger can be found in LongMath and BigIntegerMath respectively. For other common operations on int values, see Ints.

Since:

11.0

Author:

Louis Wasserman

Method Summary

static int	binomial(int n, int k) Returns n choose k, also known as the binomial coefficient of n and k, or Integer.MAX_VALUE if the result does not fit in an int.
static int	checkedAdd(int a, int b) Returns the sum of a and b, provided it does not overflow.
static int	checkedMultiply(int a, int b) Returns the product of a and b, provided it does not overflow.
static int	checkedPow(int b, int k) Returns the b to the kth power, provided it does not overflow.
static int	checkedSubtract(int a, int b) Returns the difference of a and b, provided it does not overflow.
static int	divide(int p, int q, RoundingMode mode) Returns the result of dividing p by q, rounding using the specified RoundingMode.
static int	factorial(int n) Returns n!, that is, the product of the first n positive integers, 1 if n == 0, or Integer.MAX_VALUE if the result does not fit in a int.
static int	gcd(int a, int b) Returns the greatest common divisor of a, b.
static boolean	isPowerOfTwo(int x) Returns true if x represents a power of two.
static int	log10(int x, RoundingMode mode) Returns the base-10 logarithm of x, rounded according to the specified rounding mode.
static int	log2(int x, RoundingMode mode) Returns the base-2 logarithm of x, rounded according to the specified rounding mode.
static int	mod(int x, int m) Returns x mod m.
static int	pow(int b, int k) Returns b to the kth power.
static int	sqrt(int 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(int x)

Returns true if x represents a power of two.

This differs from Integer.bitCount(x) == 1, because Integer.bitCount(Integer.MIN_VALUE) == 1, but Integer.MIN_VALUE is not a power of two.

log2

public static int log2(int 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

@GwtIncompatible(value="need BigIntegerMath to adequately test")
public static int log10(int 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

@GwtIncompatible(value="failing tests")
public static int pow(int b,
                                           int k)

Returns b to the kth power. Even if the result overflows, it will be equal to BigInteger.valueOf(b).pow(k).intValue(). This implementation runs in O(log k) time.

Compare checkedPow(int, int), which throws an ArithmeticException upon overflow.

Throws:

IllegalArgumentException - if k < 0

sqrt

@GwtIncompatible(value="need BigIntegerMath to adequately test")
public static int sqrt(int 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 int divide(int p,
                         int 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(int 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

gcd

public static int gcd(int a,
                      int 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 int checkedAdd(int a,
                             int b)

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

Throws:

ArithmeticException - if a + b overflows in signed int arithmetic

checkedSubtract

public static int checkedSubtract(int a,
                                  int b)

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

Throws:

ArithmeticException - if a - b overflows in signed int arithmetic

checkedMultiply

public static int checkedMultiply(int a,
                                  int b)

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

Throws:

ArithmeticException - if a * b overflows in signed int arithmetic

checkedPow

public static int checkedPow(int b,
                             int k)

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

pow(int, int) may be faster, but does not check for overflow.

Throws:

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

factorial

public static int factorial(int n)

Returns n!, that is, the product of the first n positive integers, 1 if n == 0, or Integer.MAX_VALUE if the result does not fit in a int.

Throws:

IllegalArgumentException - if n < 0

binomial

@GwtIncompatible(value="need BigIntegerMath to adequately test")
public static int binomial(int n,
                                                int k)

Returns n choose k, also known as the binomial coefficient of n and k, or Integer.MAX_VALUE if the result does not fit in an int.

Throws:

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