is new.
java.lang.Objectjava.lang.Math
public final class Math
The class 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.
| Field Summary | |
|---|---|
| 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. |
| Method Summary | |
|---|---|
| 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
|
| static double |
asin
(double a) Returns the arc sine of
a value; the returned angle is
|
| static double |
atan
(double a) Returns the arc tangent of
a value; the returned angle is
|
| static double |
atan2
(double y, double x)
Returns the angle
theta
from the conversion of
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 e x -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( x 2 + y 2 ) 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. |
| static int |
round
(float a) Returns the closest int to the argument. |
static double
|
scalb
(double d, int scaleFactor)
Return d × 2
scaleFactor
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 × 2
scaleFactor
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. |
| Methods inherited from class java.lang. Object |
|---|
| clone , equals , finalize , getClass , hashCode , notify , notifyAll , toString , wait , wait , wait |
| Field Detail |
|---|
public static final double E
public static final double PI
| Method Detail |
|---|
public static double sin(double a)
The computed result must be within 1 ulp of the exact result. Results must be semi-monotonic.
public static double cos(double a)
The computed result must be within 1 ulp of the exact result. Results must be semi-monotonic.
public static double tan(double a)
The computed result must be within 1 ulp of the exact result. Results must be semi-monotonic.
public static double asin(double a)
a value; the returned angle is
The computed result must be within 1 ulp of the exact result. Results must be semi-monotonic.
public static double acos(double a)
a value; the returned angle is
The computed result must be within 1 ulp of the exact result. Results must be semi-monotonic.
public static double atan(double a)
a value; the returned angle is
The computed result must be within 1 ulp of the exact result. Results must be semi-monotonic.
public static double toRadians(double angdeg)
public static double toDegrees(double angrad)
public static double exp(double a)
The computed result must be within 1 ulp of the exact result. Results must be semi-monotonic.
public static double log(double a)
The computed result must be within 1 ulp of the exact result. Results must be semi-monotonic.
public static double log10(double a)
The computed result must be within 1 ulp of the exact result. Results must be semi-monotonic.
public static double sqrt(double a)
public static double cbrt(double a)
The computed result must be within 1 ulp of the exact result.
public static double IEEEremainder(double f1,
double f2)
public static double ceil(double a)
public static double floor(double a)
public static double rint(double a)
public static double atan2(double y,
double x)
Returns the angle
from the conversion of rectangular coordinates (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: The computed result must be within 2 ulps of the exact result. Results must be semi-monotonic.
public static double pow(double a,
double b)
(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.
public static int round(float a)
(int)Math.floor(a + 0.5f)
Special cases:
public static long round(double a)
(long)Math.floor(a + 0.5d)
Special cases:
public static double random()
When this method is first called, it creates a single new pseudorandom-number generator, exactly as if by the expression
This new pseudorandom-number generator is used thereafter for all calls to this method and is used nowhere else.new java.util.Random
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.
public static int abs(int a)
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.
public static long abs(long a)
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.
public static float abs(float a)
Float.intBitsToFloat(0x7fffffff & Float.floatToIntBits(a))
public static double abs(double a)
Double.longBitsToDouble((Double.doubleToLongBits(a)<<1)>>>1)
public static int max(int a,
int b)
public static long max(long a,
long b)
public static float max(float a,
float b)
public static double max(double a,
double b)
public static int min(int a,
int b)
public static long min(long a,
long b)
public static float min(float a,
float b)
public static double min(double a,
double b)
public static double ulp(double d)
Special Cases:
public static float ulp(float f)
Special Cases:
public static double signum(double d)
Special Cases:
public static float signum(float f)
Special Cases:
public static double sinh(double x)
Special cases:
The computed result must be within 2.5 ulps of the exact result.
public static double cosh(double x)
Special cases:
The computed result must be within 2.5 ulps of the exact result.
public static double tanh(double x)
Special cases:
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.
public 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.
public static double expm1(double 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 e x - 1 is within 1/2 ulp of the limit value -1, -1.0 should be returned.
Since:
1.5
public static double log1p(double x)
Special cases:
The computed result must be within 1 ulp of the exact result. Results must be semi-monotonic.
Since:
1.5
copySign
public static double
copySign
(double magnitude, double sign)
Returns the first floating-point argument with the sign of the second floating-point argument. Note that unlike the
StrictMath.copySign
method, this method does not require NaN sign arguments to be treated as positive values; implementations are permitted to treat some NaN arguments as positive and other NaN arguments as negative to allow greater performance.
Parameters:
magnitude - the parameter providing the magnitude of the result
sign - the parameter providing the sign of the result
Returns:
a value with the magnitude of magnitude and the sign of sign.
Since:
1.6
copySign
public static float
copySign
(float magnitude, float sign)
Returns the first floating-point argument with the sign of the second floating-point argument. Note that unlike the
StrictMath.copySign
method, this method does not require NaN sign arguments to be treated as positive values; implementations are permitted to treat some NaN arguments as positive and other NaN arguments as negative to allow greater performance.
Parameters:
magnitude - the parameter providing the magnitude of the result
sign - the parameter providing the sign of the result
Returns:
a value with the magnitude of magnitude and the sign of sign.
Since:
1.6
getExponent
public static int
getExponent
(float f)
Returns the unbiased exponent used in the representation of a float. Special cases:
If the argument is NaN or infinite, then the result is
Float.MAX_EXPONENT
+ 1.
If the argument is zero or subnormal, then the result is
Float.MIN_EXPONENT
-1.
Parameters:
f - a float value
Returns:
the unbiased exponent of the argument
Since:
1.6
getExponent
public static int
getExponent
(double d)
Returns the unbiased exponent used in the representation of a double. Special cases:
If the argument is NaN or infinite, then the result is
Double.MAX_EXPONENT
+ 1.
If the argument is zero or subnormal, then the result is
Double.MIN_EXPONENT
-1.
Parameters:
d - a double value
Returns:
the unbiased exponent of the argument
Since:
1.6
nextAfter
public static double
nextAfter
(double start, double direction)
Returns the floating-point number adjacent to the first argument in the direction of the second argument. If both arguments compare as equal the second argument is returned.
If either argument is a NaN, then NaN is returned.
If both arguments are signed zeros, direction is returned unchanged (as implied by the requirement of returning the second argument if the arguments compare as equal).
If 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.
If 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.
If 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.
Parameters:
start - starting floating-point value
direction - value indicating which of start's neighbors or start should be returned
Returns:
The floating-point number adjacent to start in the direction of direction.
Since:
1.6
nextAfter
public static float
nextAfter
(float start, double direction)
Returns the floating-point number adjacent to the first argument in the direction of the second argument. If both arguments compare as equal a value equivalent to the second argument is returned.
If either argument is a NaN, then NaN is returned.
If both arguments are signed zeros, a value equivalent to direction is returned.
If 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.
If 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.
If 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.
Parameters:
start - starting floating-point value
direction - value indicating which of start's neighbors or start should be returned
Returns:
The floating-point number adjacent to start in the direction of direction.
Since:
1.6
nextUp
public static double
nextUp
(double d)
Returns the floating-point value adjacent to 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.
If the argument is NaN, the result is NaN.
If the argument is positive infinity, the result is positive infinity.
If the argument is zero, the result is
Double.MIN_VALUE
Parameters:
d - starting floating-point value
Returns:
The adjacent floating-point value closer to positive infinity.
Since:
1.6
nextUp
public static float
nextUp
(float f)
Returns the floating-point value adjacent to 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.
If the argument is NaN, the result is NaN.
If the argument is positive infinity, the result is positive infinity.
If the argument is zero, the result is
Float.MIN_VALUE
Parameters:
f - starting floating-point value
Returns:
The adjacent floating-point value closer to positive infinity.
Since:
1.6
scalb
public static double
scalb
(double d, int scaleFactor)
Return d × 2
scaleFactor
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.
If the first argument is NaN, NaN is returned.
If the first argument is infinite, then an infinity of the same sign is returned.
If the first argument is zero, then a zero of the same sign is returned.
Parameters:
d - number to be scaled by a power of two.
scaleFactor - power of 2 used to scale d
Returns:
d × 2
scaleFactor
Since:
1.6
scalb
public static float
scalb
(float f, int scaleFactor)
Return f × 2
scaleFactor
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.
If the first argument is NaN, NaN is returned.
If the first argument is infinite, then an infinity of the same sign is returned.
If the first argument is zero, then a zero of the same sign is returned.
Parameters:
f - number to be scaled by a power of two.
scaleFactor - power of 2 used to scale f
Returns:
f × 2
scaleFactor
Since:
1.6