public final class Math extends Object
Math
contains methods for performing basic numeric operations such as the
elementary exponential, logarithm, square root, and trigonometric functions.
Unlike some of the numeric methods of class StrictMath
, all implementations of the
equivalent functions of class Math
are not defined to return the bit-for-bit same
results. This relaxation permits better-performing implementations where strict reproducibility
is not required.
By default many of the Math
methods simply call the equivalent method in
StrictMath
for their implementation. Code generators are encouraged to use
platform-specific native libraries or microprocessor instructions, where available, to provide
higher-performance implementations of Math
methods. Such higher-performance
implementations still must conform to the specification for Math
.
The quality of implementation specifications concern two properties, accuracy of the returned
result and monotonicity of the method. Accuracy of the floating-point Math
methods is
measured in terms of ulps, units in the last place. For a given floating-point format, an
ulp of a specific real number value is the distance between the two floating-point values
bracketing that numerical value. When discussing the accuracy of a method as a whole rather than
at a specific argument, the number of ulps cited is for the worst-case error at any argument. If
a method always has an error less than 0.5 ulps, the method always returns the floating-point
number nearest the exact result; such a method is correctly rounded. A correctly rounded
method is generally the best a floating-point approximation can be; however, it is impractical
for many floating-point methods to be correctly rounded. Instead, for the Math
class, a
larger error bound of 1 or 2 ulps is allowed for certain methods. Informally, with a 1 ulp error
bound, when the exact result is a representable number, the exact result should be returned as
the computed result; otherwise, either of the two floating-point values which bracket the exact
result may be returned. For exact results large in magnitude, one of the endpoints of the bracket
may be infinite. Besides accuracy at individual arguments, maintaining proper relations between
the method at different arguments is also important. Therefore, most methods with more than 0.5
ulp errors are required to be semi-monotonic: whenever the mathematical function is
non-decreasing, so is the floating-point approximation, likewise, whenever the mathematical
function is non-increasing, so is the floating-point approximation. Not all approximations that
have 1 ulp accuracy will automatically meet the monotonicity requirements.
Modifier and Type | Field and Description |
---|---|
static double |
E
The
double value that is closer than any other to e, the base of the natural
logarithms. |
static double |
PI
The
double value that is closer than any other to pi, the ratio of the
circumference of a circle to its diameter. |
Modifier and Type | Method and Description |
---|---|
static double |
abs(double a)
Returns the absolute value of a
double value. |
static float |
abs(float a)
Returns the absolute value of a
float value. |
static int |
abs(int a)
Returns the absolute value of an
int value. |
static long |
abs(long a)
Returns the absolute value of a
long value. |
static double |
acos(double a)
Returns the arc cosine of a value; the returned angle is in the range 0.0 through pi.
|
static double |
asin(double a)
Returns the arc sine of a value; the returned angle is in the range -pi/2 through
pi/2.
|
static double |
atan(double a)
Returns the arc tangent of a value; the returned angle is in the range -pi/2 through
pi/2.
|
static double |
atan2(double y,
double x)
Returns the angle theta from the conversion of rectangular coordinates (
x
, y ) to polar coordinates (r, theta). |
static double |
cbrt(double a)
Returns the cube root of a
double value. |
static double |
ceil(double a)
Returns the smallest (closest to negative infinity)
double value that is greater than or
equal to the argument and is equal to a mathematical integer. |
static double |
copySign(double magnitude,
double sign)
Returns the first floating-point argument with the sign of the second floating-point argument.
|
static float |
copySign(float magnitude,
float sign)
Returns the first floating-point argument with the sign of the second floating-point argument.
|
static double |
cos(double a)
Returns the trigonometric cosine of an angle.
|
static double |
cosh(double x)
Returns the hyperbolic cosine of a
double value. |
static double |
exp(double a)
Returns Euler's number e raised to the power of a
double value. |
static double |
expm1(double x)
Returns ex -1.
|
static double |
floor(double a)
Returns the largest (closest to positive infinity)
double value that is less than or
equal to the argument and is equal to a mathematical integer. |
static int |
getExponent(double d)
Returns the unbiased exponent used in the representation of a
double . |
static int |
getExponent(float f)
Returns the unbiased exponent used in the representation of a
float . |
static double |
hypot(double x,
double y)
Returns sqrt(x2 +y2) without intermediate overflow or
underflow.
|
static double |
IEEEremainder(double f1,
double f2)
Computes the remainder operation on two arguments as prescribed by the IEEE 754 standard.
|
static double |
log(double a)
Returns the natural logarithm (base e) of a
double value. |
static double |
log10(double a)
Returns the base 10 logarithm of a
double value. |
static double |
log1p(double x)
Returns the natural logarithm of the sum of the argument and 1.
|
static double |
max(double a,
double b)
Returns the greater of two
double values. |
static float |
max(float a,
float b)
Returns the greater of two
float values. |
static int |
max(int a,
int b)
Returns the greater of two
int values. |
static long |
max(long a,
long b)
Returns the greater of two
long values. |
static double |
min(double a,
double b)
Returns the smaller of two
double values. |
static float |
min(float a,
float b)
Returns the smaller of two
float values. |
static int |
min(int a,
int b)
Returns the smaller of two
int values. |
static long |
min(long a,
long b)
Returns the smaller of two
long values. |
static double |
nextAfter(double start,
double direction)
Returns the floating-point number adjacent to the first argument in the direction of the second
argument.
|
static float |
nextAfter(float start,
double direction)
Returns the floating-point number adjacent to the first argument in the direction of the second
argument.
|
static double |
nextUp(double d)
Returns the floating-point value adjacent to
d in the direction of positive infinity. |
static float |
nextUp(float f)
Returns the floating-point value adjacent to
f in the direction of positive infinity. |
static double |
pow(double a,
double b)
Returns the value of the first argument raised to the power of the second argument.
|
static double |
random()
Returns a
double value with a positive sign, greater than or equal to 0.0 and
less than 1.0 . |
static double |
rint(double a)
Returns the
double value that is closest in value to the argument and is equal to a
mathematical integer. |
static long |
round(double a)
Returns the closest
long to the argument, with ties rounding up. |
static int |
round(float a)
Returns the closest
int to the argument, with ties rounding up. |
static double |
scalb(double d,
int scaleFactor)
Return
d × 2scaleFactor rounded as if performed by a single
correctly rounded floating-point multiply to a member of the double value set. |
static float |
scalb(float f,
int scaleFactor)
Return
f × 2scaleFactor rounded as if performed by a single
correctly rounded floating-point multiply to a member of the float value set. |
static double |
signum(double d)
Returns the signum function of the argument; zero if the argument is zero, 1.0 if the argument is
greater than zero, -1.0 if the argument is less than zero.
|
static float |
signum(float f)
Returns the signum function of the argument; zero if the argument is zero, 1.0f if the argument
is greater than zero, -1.0f if the argument is less than zero.
|
static double |
sin(double a)
Returns the trigonometric sine of an angle.
|
static double |
sinh(double x)
Returns the hyperbolic sine of a
double value. |
static double |
sqrt(double a)
Returns the correctly rounded positive square root of a
double value. |
static double |
tan(double a)
Returns the trigonometric tangent of an angle.
|
static double |
tanh(double x)
Returns the hyperbolic tangent of a
double value. |
static double |
toDegrees(double angrad)
Converts an angle measured in radians to an approximately equivalent angle measured in degrees.
|
static double |
toRadians(double angdeg)
Converts an angle measured in degrees to an approximately equivalent angle measured in radians.
|
static double |
ulp(double d)
Returns the size of an ulp of the argument.
|
static float |
ulp(float f)
Returns the size of an ulp of the argument.
|
public static final double E
double
value that is closer than any other to e, the base of the natural
logarithms.public static final double PI
double
value that is closer than any other to pi, the ratio of the
circumference of a circle to its diameter.public static double abs(double a)
double
value. If the argument is not negative, the
argument is returned. If the argument is negative, the negation of the argument is returned.
Special cases:
Double.longBitsToDouble((Double.doubleToLongBits(a)<<1)>>>1)
a
- the argument whose absolute value is to be determinedpublic static float abs(float a)
float
value. If the argument is not negative, the
argument is returned. If the argument is negative, the negation of the argument is returned.
Special cases:
Float.intBitsToFloat(0x7fffffff & Float.floatToIntBits(a))
a
- the argument whose absolute value is to be determinedpublic static int abs(int a)
int
value. If the argument is not negative, the argument
is returned. If the argument is negative, the negation of the argument is returned.
Note that if the argument is equal to the value of Integer.MIN_VALUE
, the most negative
representable int
value, the result is that same value, which is negative.
a
- the argument whose absolute value is to be determinedpublic static long abs(long a)
long
value. If the argument is not negative, the argument
is returned. If the argument is negative, the negation of the argument is returned.
Note that if the argument is equal to the value of Long.MIN_VALUE
, the most negative
representable long
value, the result is that same value, which is negative.
a
- the argument whose absolute value is to be determinedpublic static double acos(double a)
The computed result must be within 1 ulp of the exact result. Results must be semi-monotonic.
a
- the value whose arc cosine is to be returned.public static double asin(double a)
The computed result must be within 1 ulp of the exact result. Results must be semi-monotonic.
a
- the value whose arc sine is to be returned.public static double atan(double a)
The computed result must be within 1 ulp of the exact result. Results must be semi-monotonic.
a
- the value whose arc tangent is to be returned.public static double atan2(double y, double x)
x
, y
) to polar coordinates (r, theta). This method computes the phase
theta by computing an arc tangent of y/x
in the range of -pi to pi.
Special cases:
double
value closest to pi.
double
value closest to -pi.
double
value closest to pi/2.
double
value closest to -pi/2.
double
value closest
to pi/4.
double
value closest to 3*pi/4.
double
value closest to -pi/4.
double
value closest
to -3*pi/4.
The computed result must be within 2 ulps of the exact result. Results must be semi-monotonic.
y
- the ordinate coordinatex
- the abscissa coordinatepublic static double cbrt(double a)
double
value. For positive finite x
,
cbrt(-x) ==
-cbrt(x)
; that is, the cube root of a negative value is the negative of the cube root of that
value's magnitude.
Special cases:
The computed result must be within 1 ulp of the exact result.
a
- a value.a
.public static double ceil(double a)
double
value that is greater than or
equal to the argument and is equal to a mathematical integer. Special cases:
Math.ceil(x)
is exactly the value of -Math.floor(-x)
.a
- a value.public static double copySign(double magnitude, double sign)
magnitude
- the parameter providing the magnitude of the resultsign
- the parameter providing the sign of the resultmagnitude
and the sign of sign
.public static float copySign(float magnitude, float sign)
magnitude
- the parameter providing the magnitude of the resultsign
- the parameter providing the sign of the resultmagnitude
and the sign of sign
.public static double cos(double a)
The computed result must be within 1 ulp of the exact result. Results must be semi-monotonic.
a
- an angle, in radians.public static double cosh(double x)
double
value. The hyperbolic cosine of x is
defined to be (ex + e-x)/2 where e is
Euler's number.
Special cases:
1.0
.
The computed result must be within 2.5 ulps of the exact result.
x
- The number whose hyperbolic cosine is to be returned.x
.public static double exp(double a)
double
value. Special cases:
The computed result must be within 1 ulp of the exact result. Results must be semi-monotonic.
a
- the exponent to raise e to.a
, where e is the base of the natural
logarithms.public static double expm1(double x)
expm1(x)
+ 1 is much closer to the true result of ex than
exp(x)
.
Special cases:
The computed result must be within 1 ulp of the exact result. Results must be semi-monotonic. The
result of expm1
for any finite input must be greater than or equal to -1.0
. Note
that once the exact result of ex
- 1 is within 1/2 ulp of the
limit value -1, -1.0
should be returned.
x
- the exponent to raise e to in the computation of ex
-1.x
- 1.public static double floor(double a)
double
value that is less than or
equal to the argument and is equal to a mathematical integer. Special cases:
a
- a value.public static int getExponent(double d)
double
. Special cases:
Double.MAX_EXPONENT
+ 1.
Double.MIN_EXPONENT
-1.
d
- a double
valuepublic static int getExponent(float f)
float
. Special cases:
Float.MAX_EXPONENT
+ 1.
Float.MIN_EXPONENT
-1.
f
- a float
valuepublic static double hypot(double x, double y)
Special cases:
The computed result must be within 1 ulp of the exact result. If one parameter is held constant, the results must be semi-monotonic in the other parameter.
x
- a valuey
- a valuepublic static double IEEEremainder(double f1, double f2)
f1 - f2
× n, where n is the mathematical integer closest to the exact
mathematical value of the quotient f1/f2
, and if two mathematical integers are equally
close to f1/f2
, then n is the integer that is even. If the remainder is zero, its
sign is the same as the sign of the first argument. Special cases:
f1
- the dividend.f2
- the divisor.f1
is divided by f2
.public static double log(double a)
double
value. Special cases:
The computed result must be within 1 ulp of the exact result. Results must be semi-monotonic.
a
- a valuea
, the natural logarithm of a
.public static double log10(double a)
double
value. Special cases:
The computed result must be within 1 ulp of the exact result. Results must be semi-monotonic.
a
- a valuea
.public static double log1p(double x)
x
, the result of log1p(x)
is much closer to the true result of ln(1 + x
)
than the floating-point evaluation of log(1.0+x)
.
Special cases:
The computed result must be within 1 ulp of the exact result. Results must be semi-monotonic.
x
- a valuex
+ 1), the natural log of x
+ 1public static double max(double a, double b)
double
values. That is, the result is the argument closer to
positive infinity. If the arguments have the same value, the result is that same value. If either
value is NaN, then the result is NaN. Unlike the numerical comparison operators, this method
considers negative zero to be strictly smaller than positive zero. If one argument is positive
zero and the other negative zero, the result is positive zero.a
- an argument.b
- another argument.a
and b
.public static float max(float a, float b)
float
values. That is, the result is the argument closer to
positive infinity. If the arguments have the same value, the result is that same value. If either
value is NaN, then the result is NaN. Unlike the numerical comparison operators, this method
considers negative zero to be strictly smaller than positive zero. If one argument is positive
zero and the other negative zero, the result is positive zero.a
- an argument.b
- another argument.a
and b
.public static int max(int a, int b)
int
values. That is, the result is the argument closer to the
value of Integer.MAX_VALUE
. If the arguments have the same value, the result is that same
value.a
- an argument.b
- another argument.a
and b
.public static long max(long a, long b)
long
values. That is, the result is the argument closer to the
value of Long.MAX_VALUE
. If the arguments have the same value, the result is that same
value.a
- an argument.b
- another argument.a
and b
.public static double min(double a, double b)
double
values. That is, the result is the value closer to
negative infinity. If the arguments have the same value, the result is that same value. If either
value is NaN, then the result is NaN. Unlike the numerical comparison operators, this method
considers negative zero to be strictly smaller than positive zero. If one argument is positive
zero and the other is negative zero, the result is negative zero.a
- an argument.b
- another argument.a
and b
.public static float min(float a, float b)
float
values. That is, the result is the value closer to
negative infinity. If the arguments have the same value, the result is that same value. If either
value is NaN, then the result is NaN. Unlike the numerical comparison operators, this method
considers negative zero to be strictly smaller than positive zero. If one argument is positive
zero and the other is negative zero, the result is negative zero.a
- an argument.b
- another argument.a
and b
.public static int min(int a, int b)
int
values. That is, the result the argument closer to the
value of Integer.MIN_VALUE
. If the arguments have the same value, the result is that same
value.a
- an argument.b
- another argument.a
and b
.public static long min(long a, long b)
long
values. That is, the result is the argument closer to the
value of Long.MIN_VALUE
. If the arguments have the same value, the result is that same
value.a
- an argument.b
- another argument.a
and b
.public static double nextAfter(double start, double direction)
Special cases:
direction
is returned unchanged (as implied by
the requirement of returning the second argument if the arguments compare as equal).
start
is ±Double.MIN_VALUE
and direction
has a value such
that the result should have a smaller magnitude, then a zero with the same sign as start
is returned.
start
is infinite and direction
has a value such that the result should
have a smaller magnitude, Double.MAX_VALUE
with the same sign as start
is
returned.
start
is equal to ± Double.MAX_VALUE
and direction
has a
value such that the result should have a larger magnitude, an infinity with same sign as
start
is returned.
start
- starting floating-point valuedirection
- value indicating which of start
's neighbors or start
should be returnedstart
in the direction of
direction
.public static float nextAfter(float start, double direction)
Special cases:
direction
is returned.
start
is ±Float.MIN_VALUE
and direction
has a value such
that the result should have a smaller magnitude, then a zero with the same sign as start
is returned.
start
is infinite and direction
has a value such that the result should
have a smaller magnitude, Float.MAX_VALUE
with the same sign as start
is
returned.
start
is equal to ± Float.MAX_VALUE
and direction
has a
value such that the result should have a larger magnitude, an infinity with same sign as
start
is returned.
start
- starting floating-point valuedirection
- value indicating which of start
's neighbors or start
should be returnedstart
in the direction of
direction
.public static double nextUp(double d)
d
in the direction of positive infinity.
This method is semantically equivalent to nextAfter(d,
Double.POSITIVE_INFINITY)
; however, a nextUp
implementation may run faster than its
equivalent nextAfter
call.
Special Cases:
Double.MIN_VALUE
d
- starting floating-point valuepublic static float nextUp(float f)
f
in the direction of positive infinity.
This method is semantically equivalent to nextAfter(f,
Float.POSITIVE_INFINITY)
; however, a nextUp
implementation may run faster than its
equivalent nextAfter
call.
Special Cases:
Float.MIN_VALUE
f
- starting floating-point valuepublic static double pow(double a, double b)
double
value.
(In the foregoing descriptions, a floating-point value is considered to be an integer if and only
if it is finite and a fixed point of the method ceil
or, equivalently, a fixed
point of the method floor
. A value is a fixed point of a one-argument method if
and only if the result of applying the method to the value is equal to the value.)
The computed result must be within 1 ulp of the exact result. Results must be semi-monotonic.
a
- the base.b
- the exponent.a
b
.public static double random()
double
value with a positive sign, greater than or equal to 0.0
and
less than 1.0
. Returned values are chosen pseudorandomly with (approximately) uniform
distribution from that range.
When this method is first called, it creates a single new pseudorandom-number generator, exactly as if by the expression
new java.util.Random()
This new pseudorandom-number generator is used thereafter for all calls to this method and is
used nowhere else.
This method is properly synchronized to allow correct use by more than one thread. However, if many threads need to generate pseudorandom numbers at a great rate, it may reduce contention for each thread to have its own pseudorandom-number generator.
double
greater than or equal to 0.0
and less than
1.0
.Random.nextDouble()
public static double rint(double a)
double
value that is closest in value to the argument and is equal to a
mathematical integer. If two double
values that are mathematical integers are equally
close, the result is the integer value that is even. Special cases:
a
- a double
value.a
that is equal to a mathematical integer.public static long round(double a)
long
to the argument, with ties rounding up.
Special cases:
Long.MIN_VALUE
, the result is equal to the value of Long.MIN_VALUE
.
Long.MAX_VALUE
, the result is equal to the value of Long.MAX_VALUE
.
a
- a floating-point value to be rounded to a long
.long
value.Long.MAX_VALUE
,
Long.MIN_VALUE
public static int round(float a)
int
to the argument, with ties rounding up.
Special cases:
Integer.MIN_VALUE
, the result is equal to the value of Integer.MIN_VALUE
.
Integer.MAX_VALUE
, the result is equal to the value of Integer.MAX_VALUE
.
a
- a floating-point value to be rounded to an integer.int
value.Integer.MAX_VALUE
,
Integer.MIN_VALUE
public static double scalb(double d, int scaleFactor)
d
× 2scaleFactor
rounded as if performed by a single
correctly rounded floating-point multiply to a member of the double value set. See the Java
Language Specification for a discussion of floating-point value sets. If the exponent of the
result is between Double.MIN_EXPONENT
and Double.MAX_EXPONENT
, the answer is
calculated exactly. If the exponent of the result would be larger than
Double.MAX_EXPONENT
, an infinity is returned. Note that if the result is subnormal,
precision may be lost; that is, when scalb(x, n)
is subnormal,
scalb(scalb(x, n), -n)
may not equal x. When the result is non-NaN, the result has
the same sign as d
.
Special cases:
d
- number to be scaled by a power of two.scaleFactor
- power of 2 used to scale d
d
× 2scaleFactor
public static float scalb(float f, int scaleFactor)
f
× 2scaleFactor
rounded as if performed by a single
correctly rounded floating-point multiply to a member of the float value set. See the Java
Language Specification for a discussion of floating-point value sets. If the exponent of the
result is between Float.MIN_EXPONENT
and Float.MAX_EXPONENT
, the answer is
calculated exactly. If the exponent of the result would be larger than
Float.MAX_EXPONENT
, an infinity is returned. Note that if the result is subnormal,
precision may be lost; that is, when scalb(x, n)
is subnormal,
scalb(scalb(x, n), -n)
may not equal x. When the result is non-NaN, the result has
the same sign as f
.
Special cases:
f
- number to be scaled by a power of two.scaleFactor
- power of 2 used to scale f
f
× 2scaleFactor
public static double signum(double d)
Special Cases:
d
- the floating-point value whose signum is to be returnedpublic static float signum(float f)
Special Cases:
f
- the floating-point value whose signum is to be returnedpublic static double sin(double a)
The computed result must be within 1 ulp of the exact result. Results must be semi-monotonic.
a
- an angle, in radians.public static double sinh(double x)
double
value. The hyperbolic sine of x is defined
to be (ex - e-x)/2 where e is Euler's number.
Special cases:
The computed result must be within 2.5 ulps of the exact result.
x
- The number whose hyperbolic sine is to be returned.x
.public static double sqrt(double a)
double
value. Special cases:
double
value closest to the true mathematical square root of
the argument value.a
- a value.a
. If the argument is NaN or less than zero, the
result is NaN.public static double tan(double a)
The computed result must be within 1 ulp of the exact result. Results must be semi-monotonic.
a
- an angle, in radians.public static double tanh(double x)
double
value. The hyperbolic tangent of x is
defined to be (ex - e-x)/(ex +
e-x), in other words, sinh(x)/
cosh(x). Note that the absolute value of the exact tanh is always
less than 1.
Special cases:
+1.0
.
-1.0
.
The computed result must be within 2.5 ulps of the exact result. The result of tanh
for
any finite input must have an absolute value less than or equal to 1. Note that once the exact
result of tanh is within 1/2 of an ulp of the limit value of ±1, correctly signed
±1.0
should be returned.
x
- The number whose hyperbolic tangent is to be returned.x
.public static double toDegrees(double angrad)
cos(toRadians(90.0))
to exactly equal 0.0
.angrad
- an angle, in radiansangrad
in degrees.public static double toRadians(double angdeg)
angdeg
- an angle, in degreesangdeg
in radians.public static double ulp(double d)
double
value is the positive
distance between this floating-point value and the double
value next larger in magnitude.
Note that for non-NaN x, ulp(-x) == ulp(x)
.
Special Cases:
Double.MIN_VALUE
.
Double.MAX_VALUE
, then the result is equal to
2971.
d
- the floating-point value whose ulp is to be returnedpublic static float ulp(float f)
float
value is the positive
distance between this floating-point value and the float
value next larger in magnitude.
Note that for non-NaN x, ulp(-x) == ulp(x)
.
Special Cases:
Float.MIN_VALUE
.
Float.MAX_VALUE
, then the result is equal to
2104.
f
- the floating-point value whose ulp is to be returned