@GwtCompatible(emulated=true) public final class IntMath extends Object
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
.
Modifier and Type | Method and Description |
---|---|
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 |
ceilingPowerOfTwo(int x)
Returns the smallest power of two greater than or equal to
x . |
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 k th 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 |
floorPowerOfTwo(int x)
Returns the largest power of two less than or equal to
x . |
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 boolean |
isPrime(int n)
Returns
true if n is a prime number: an integer greater
than one that cannot be factored into a product of smaller positive integers. |
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 |
mean(int x,
int y)
Returns the arithmetic mean of
x and y , rounded towards negative infinity. |
static int |
mod(int x,
int m)
Returns
x mod m , a non-negative value less than m . |
static int |
pow(int b,
int k)
Returns
b to the k th power. |
static int |
saturatedAdd(int a,
int b)
Returns the sum of
a and b unless it would overflow or underflow in which case
Integer.MAX_VALUE or Integer.MIN_VALUE is returned, respectively. |
static int |
saturatedMultiply(int a,
int b)
Returns the product of
a and b unless it would overflow or underflow in which
case Integer.MAX_VALUE or Integer.MIN_VALUE is returned, respectively. |
static int |
saturatedPow(int b,
int k)
Returns the
b to the k th power, unless it would overflow or underflow in which
case Integer.MAX_VALUE or Integer.MIN_VALUE is returned, respectively. |
static int |
saturatedSubtract(int a,
int b)
Returns the difference of
a and b unless it would overflow or underflow in
which case Integer.MAX_VALUE or Integer.MIN_VALUE is returned, respectively. |
static int |
sqrt(int x,
RoundingMode mode)
Returns the square root of
x , rounded with the specified rounding mode. |
@Beta public static int ceilingPowerOfTwo(int x)
x
. This is equivalent to
checkedPow(2, log2(x, CEILING))
.IllegalArgumentException
- if x <= 0
ArithmeticException
- of the next-higher power of two is not representable as an int
, i.e. when x > 2^30
@Beta public static int floorPowerOfTwo(int x)
x
. This is equivalent to checkedPow(2, log2(x, FLOOR))
.IllegalArgumentException
- if x <= 0
public static boolean isPowerOfTwo(int x)
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.
public static int log2(int 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@GwtIncompatible public static int log10(int 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@GwtIncompatible public static int pow(int b, int k)
b
to the k
th 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.
IllegalArgumentException
- if k < 0
@GwtIncompatible public static int sqrt(int 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 integerpublic static int divide(int p, int 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(int x, int m)
x mod m
, a non-negative value less than m
. This differs from x %
m
, which might be negative.
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 int gcd(int a, int b)
a, b
. Returns 0
if a == 0 && b ==
0
.IllegalArgumentException
- if a < 0
or b < 0
public static int checkedAdd(int a, int b)
a
and b
, provided it does not overflow.ArithmeticException
- if a + b
overflows in signed int
arithmeticpublic static int checkedSubtract(int a, int b)
a
and b
, provided it does not overflow.ArithmeticException
- if a - b
overflows in signed int
arithmeticpublic static int checkedMultiply(int a, int b)
a
and b
, provided it does not overflow.ArithmeticException
- if a * b
overflows in signed int
arithmeticpublic static int checkedPow(int b, int k)
b
to the k
th power, provided it does not overflow.
pow(int, int)
may be faster, but does not check for overflow.
ArithmeticException
- if b
to the k
th power overflows in signed int
arithmetic@Beta public static int saturatedAdd(int a, int b)
a
and b
unless it would overflow or underflow in which case
Integer.MAX_VALUE
or Integer.MIN_VALUE
is returned, respectively.@Beta public static int saturatedSubtract(int a, int b)
a
and b
unless it would overflow or underflow in
which case Integer.MAX_VALUE
or Integer.MIN_VALUE
is returned, respectively.@Beta public static int saturatedMultiply(int a, int b)
a
and b
unless it would overflow or underflow in which
case Integer.MAX_VALUE
or Integer.MIN_VALUE
is returned, respectively.@Beta public static int saturatedPow(int b, int k)
b
to the k
th power, unless it would overflow or underflow in which
case Integer.MAX_VALUE
or Integer.MIN_VALUE
is returned, respectively.public static int factorial(int n)
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
.IllegalArgumentException
- if n < 0
public static int binomial(int n, int k)
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
.IllegalArgumentException
- if n < 0
, k < 0
or k > n
public static int mean(int x, int y)
x
and y
, rounded towards negative infinity. This
method is overflow resilient.@GwtIncompatible @Beta public static boolean isPrime(int n)
true
if n
is a prime number: an integer greater
than one that cannot be factored into a product of smaller positive integers.
Returns false
if n
is zero, one, or a composite number (one which can be
factored into smaller positive integers).
To test larger numbers, use LongMath.isPrime(long)
or BigInteger.isProbablePrime(int)
.
IllegalArgumentException
- if n
is negativeCopyright © 2010–2019. All rights reserved.