| public final class java.lang Math
|
Java SE 6 |
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.
| version | 1.72, 11/17/05 |
| since | JDK1.0 |
| Fields | |
|---|---|
| final public static double | E The double value that is closer than any other to
e, the base of the natural logarithms.
|
| final public 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.
|
| Methods | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| public static int | abs(int a) Details
Returns the absolute value of an 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
| ||||||||
| public static long | abs(long a) Details
Returns the absolute value of 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
| ||||||||
| public static float | abs(float a) Details
Returns the absolute value of 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))
| ||||||||
| public static double | abs(double a) Details
Returns the absolute value of 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:
| ||||||||
| public static double | acos(double a) Details
Returns the arc cosine of a value; the returned angle is in the
range 0.0 through pi. Special case:
The computed result must be within 1 ulp of the exact result. Results must be semi-monotonic.
| ||||||||
| public static double | asin(double a) Details
Returns the arc sine of a value; the returned angle is in the
range -pi/2 through pi/2. Special cases:
The computed result must be within 1 ulp of the exact result. Results must be semi-monotonic.
| ||||||||
| public static double | atan(double a) Details
Returns the arc tangent of a value; the returned angle is in the
range -pi/2 through pi/2. Special cases:
The computed result must be within 1 ulp of the exact result. Results must be semi-monotonic.
| ||||||||
| public static double | atan2(double y, double x) Details
Returns the angle theta 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 | cbrt(double a) Details
Returns the cube root of 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.
| ||||||||
| public static double | ceil(double a) Details
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. Special cases:
Math.ceil(x) is exactly the
value of -Math.floor(-x).
| ||||||||
| public static double | copySign(double magnitude, double sign) Details
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.
| ||||||||
| public static float | copySign(float magnitude, float sign) Details
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.
| ||||||||
| public static double | cos(double a) Details
Returns the trigonometric cosine of an angle. Special cases:
The computed result must be within 1 ulp of the exact result. Results must be semi-monotonic.
| ||||||||
| public static double | cosh(double x) Details
Returns the hyperbolic cosine of a double value.
The hyperbolic cosine 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.
| ||||||||
| public static double | exp(double a) Details
Returns Euler's number e raised to the power of a
double value. Special cases:
The computed result must be within 1 ulp of the exact result. Results must be semi-monotonic.
| ||||||||
| public static double | expm1(double x) Details
Returns ex -1. Note that for values of
x near 0, the exact sum of
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
| ||||||||
| public static double | floor(double a) Details
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. Special cases:
| ||||||||
| public static double | hypot(double x, double y) Details
Returns sqrt(x2 +y2)
without intermediate overflow or underflow.
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 | IEEEremainder(double f1, double f2) Details
Computes the remainder operation on two arguments as prescribed
by the IEEE 754 standard.
The remainder value is mathematically equal to
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:
| ||||||||
| public static double | log(double a) Details
Returns the natural logarithm (base e) of a double
value. Special cases:
The computed result must be within 1 ulp of the exact result. Results must be semi-monotonic.
| ||||||||
| public static double | log10(double a) Details
Returns the base 10 logarithm of a double value.
Special cases:
The computed result must be within 1 ulp of the exact result. Results must be semi-monotonic.
| ||||||||
| public static double | log1p(double x) Details
Returns the natural logarithm of the sum of the argument and 1.
Note that for small values 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.
| ||||||||
| public static int | max(int a, int b) Details
Returns the greater of two 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.
| ||||||||
| public static long | max(long a, long b) Details
Returns the greater of two 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.
| ||||||||
| public static float | max(float a, float b) Details
Returns the greater of two 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.
| ||||||||
| public static double | max(double a, double b) Details
Returns the greater of two 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.
| ||||||||
| public static int | min(int a, int b) Details
Returns the smaller of two 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.
| ||||||||
| public static long | min(long a, long b) Details
Returns the smaller of two 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.
| ||||||||
| public static float | min(float a, float b) Details
Returns the smaller of two 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.
| ||||||||
| public static double | min(double a, double b) Details
Returns the smaller of two 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.
| ||||||||
| public static double | nextAfter(double start, double direction) Details
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.
Special cases:
| ||||||||
| public static float | nextAfter(float start, double direction) Details
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.
Special cases:
| ||||||||
| public static double | nextUp(double d) Details
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.
Special Cases:
| ||||||||
| public static float | nextUp(float f) Details
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.
Special Cases:
| ||||||||
| public static double | pow(double a, double b) Details
Returns the value of the first argument raised to the power of the
second argument. Special cases:
(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 The computed result must be within 1 ulp of the exact result. Results must be semi-monotonic.
| ||||||||
| public static double | random() Details
Returns a 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 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 double | rint(double a) Details
Returns the 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:
| ||||||||
| public static int | round(float a) Details
Returns the closest int to the argument. The
result is rounded to an integer by adding 1/2, taking the
floor of the result, and casting the result to type int.
In other words, the result is equal to the value of the expression:
(int)Math.floor(a + 0.5f) Special cases:
| ||||||||
| public static long | round(double a) Details
Returns the closest long to the argument. The result
is rounded to an integer by adding 1/2, taking the floor of the
result, and casting the result to type long. In other
words, the result is equal to the value of the expression:
(long)Math.floor(a + 0.5d) Special cases:
| ||||||||
| public static double | scalb(double d, int scaleFactor) Details
Return 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:
| ||||||||
| public static float | scalb(float f, int scaleFactor) Details
Return 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:
| ||||||||
| public static double | signum(double d) Details
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.
Special Cases:
| ||||||||
| public static float | signum(float f) Details
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.
Special Cases:
| ||||||||
| public static double | sin(double a) Details
Returns the trigonometric sine of an angle. Special cases:
The computed result must be within 1 ulp of the exact result. Results must be semi-monotonic.
| ||||||||
| public static double | sinh(double x) Details
Returns the hyperbolic sine of a 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.
| ||||||||
| public static double | sqrt(double a) Details
Returns the correctly rounded positive square root of a
double value.
Special cases:
double value closest to
the true mathematical square root of the argument value.
| ||||||||
| public static double | tan(double a) Details
Returns the trigonometric tangent of an angle. Special cases:
The computed result must be within 1 ulp of the exact result. Results must be semi-monotonic.
| ||||||||
| public static double | tanh(double x) Details
Returns the hyperbolic tangent of a 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:
The computed result must be within 2.5 ulps of the exact result.
The result of
| ||||||||
| public static double | toDegrees(double angrad) Details
Converts an angle measured in radians to an approximately
equivalent angle measured in degrees. The conversion from
radians to degrees is generally inexact; users should
not expect cos(toRadians(90.0)) to exactly
equal 0.0.
| ||||||||
| public static double | toRadians(double angdeg) Details
Converts an angle measured in degrees to an approximately
equivalent angle measured in radians. The conversion from
degrees to radians is generally inexact.
| ||||||||
| public static double | ulp(double d) Details
Returns the size of an ulp of the argument. An ulp of a
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:
| ||||||||
| public static float | ulp(float f) Details
Returns the size of an ulp of the argument. An ulp of a
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:
| ||||||||
| Properties | |||||||
|---|---|---|---|---|---|---|---|
| public static int | getExponent(float f) Details
Returns the unbiased exponent used in the representation of a
float. Special cases:
| ||||||
| public static int | getExponent(double d) Details
Returns the unbiased exponent used in the representation of a
double. Special cases:
| ||||||
| About DocWeb · Bundles · Export · Export All | Top 10 · Statistics · Login |
| About Sun · Contact · Privacy · Terms of Use · Trademarks | Java SE 6 · Copyright © 1994-2009 Sun Microsystems, Inc.All rights reserved. Use is subject to license terms |
![]() |
![]() |
|