Class java.lang.Math - JDK 5 Documentation v1.1.8, Java 2 SDK 英文文档

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Class java.lang.Math

java.lang.Object
   |
   +----java.lang.Math

public final class Math
extends Object

The class Math contains methods for performing basic numeric operations such as the elementary exponential, logarithm, square root, and trigonometric functions.

To help ensure portability of Java programs, the definitions of many of the numeric functions in this package require that they produce the same results as certain published algorithms. These algorithms are available from the well-known network library netlib as the package "Freely Distributable Math Library" (fdlibm). These algorithms, which are written in the C programming language, are then to be understood as executed with all floating-point operations following the rules of Java floating-point arithmetic.

The network library may be found on the World Wide Web at


   http://netlib.att.com/

then perform a keyword search for "fdlibm".

The Java math library is defined with respect to the version of fdlibm dated January 4, 1995. Where fdlibm provides more than one definition for a function (such as acos), use the "IEEE 754 core function" version (residing in a file whose name begins with the letter e).

E: The double value that is closer than any other to e, the base of the natural logarithms.
PI: The double value that is closer than any other to pi, the ratio of the circumference of a circle to its diameter.

abs(double): Returns the absolute value of a double value.
abs(float): Returns the absolute value of a float value.
abs(int): Returns the absolute value of an int value.
abs(long): Returns the absolute value of a long value.
acos(double): Returns the arc cosine of an angle, in the range of 0.0 through pi.
asin(double): Returns the arc sine of an angle, in the range of -pi/2 through pi/2.
atan(double): Returns the arc tangent of an angle, in the range of -pi/2 through pi/2.
atan2(double, double): Converts rectangular coordinates (b, a) to polar (r, theta).
ceil(double): Returns the smallest (closest to negative infinity) double value that is not less than the argument and is equal to a mathematical integer.
cos(double): Returns the trigonometric cosine of an angle.
exp(double): Returns the exponential number e (i.e., 2.718...) raised to the power of a double value.
floor(double): Returns the largest (closest to positive infinity) double value that is not greater than the argument and is equal to a mathematical integer.
IEEEremainder(double, double): Computes the remainder operation on two arguments as prescribed by the IEEE 754 standard.
log(double): Returns the natural logarithm (base e) of a double value.
max(double, double): Returns the greater of two double values.
max(float, float): Returns the greater of two float values.
max(int, int): Returns the greater of two int values.
max(long, long): Returns the greater of two long values.
min(double, double): Returns the smaller of two double values.
min(float, float): Returns the smaller of two float values.
min(int, int): Returns the smaller of two int values.
min(long, long): Returns the smaller of two long values.
pow(double, double): Returns of value of the first argument raised to the power of the second argument.
random(): Returns a random number between 0.0 and 1.0.
rint(double): returns the closest integer to the argument.
round(double): Returns the closest long to the argument.
round(float): Returns the closest int to the argument.
sin(double): Returns the trigonometric sine of an angle.
sqrt(double): Returns the square root of a double value.
tan(double): Returns the trigonometric tangent of an angle.

 public static final double E

The double value that is closer than any other to e, the base of the natural logarithms.

 public static final double PI

The double value that is closer than any other to pi, the ratio of the circumference of a circle to its diameter.

sin

 public static native double sin(double a)

Returns the trigonometric sine of an angle.

Parameters:: a - an angle, in radians.
Returns:: the sine of the argument.

cos

 public static native double cos(double a)

Returns the trigonometric cosine of an angle.

Parameters:: a - an angle, in radians.
Returns:: the cosine of the argument.

tan

 public static native double tan(double a)

Returns the trigonometric tangent of an angle.

Parameters:: a - an angle, in radians.
Returns:: the tangent of the argument.

asin

 public static native double asin(double a)

Returns the arc sine of an angle, in the range of -pi/2 through pi/2.

Parameters:: a - an angle, in radians.
Returns:: the arc sine of the argument.

acos

 public static native double acos(double a)

Returns the arc cosine of an angle, in the range of 0.0 through pi.

Parameters:: a - an angle, in radians.
Returns:: the arc cosine of the argument.

atan

 public static native double atan(double a)

Returns the arc tangent of an angle, in the range of -pi/2 through pi/2.

Parameters:: a - an angle, in radians.
Returns:: the arc tangent of the argument.

exp

 public static native double exp(double a)

Returns the exponential number e (i.e., 2.718...) raised to the power of a double value.

Parameters:: a - a double value.
Returns:: the value e^a, where e is the base of the natural logarithms.

log

 public static native double log(double a)

Returns the natural logarithm (base e) of a double value.

Parameters:: a - a number greater than 0.0.
Returns:: the value ln a, the natural logarithm of a.

sqrt

 public static native double sqrt(double a)

Returns the square root of a double value.

Parameters:: a - a double value.
Returns:: the square root of a. If the argument is NaN or less than zero, the result is NaN.

IEEEremainder

 public static native double IEEEremainder(double f1,
                                           double f2)

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.

Parameters:: f1 - the dividend.; f2 - the divisor.
Returns:: the remainder when f1 is divided by f2.

ceil

 public static native double ceil(double a)

Returns the smallest (closest to negative infinity) double value that is not less than the argument and is equal to a mathematical integer.

Parameters:: a - a double value.
Returns:: the smallest (closest to negative infinity) double value that is not less than the argument and is equal to a mathematical integer.

floor

 public static native double floor(double a)

Returns the largest (closest to positive infinity) double value that is not greater than the argument and is equal to a mathematical integer.

Parameters:: a - a double value.; a - an assigned value.
Returns:: the largest (closest to positive infinity) double value that is not greater than the argument and is equal to a mathematical integer.

rint

 public static native double rint(double a)

returns the closest integer to the argument.

Parameters:: a - a double value.
Returns:: the closest double value to a that is equal to a mathematical integer. If two double values that are mathematical integers are equally close to the value of the argument, the result is the integer value that is even.

atan2

 public static native double atan2(double a,
                                   double b)

Converts rectangular coordinates (b, a) to polar (r, theta). This method computes the phase theta by computing an arc tangent of b/a in the range of -pi to pi.

Parameters:: a - a double value.; b - a double value.
Returns:: the theta component of the point (r, theta) in polar coordinates that corresponds to the point (b, a) in Cartesian coordinates.

pow

 public static native double pow(double a,
                                 double b)

Returns of value of the first argument raised to the power of the second argument.

If (a == 0.0), then b must be greater than 0.0; otherwise an exception is thrown. An exception also will occur if (a <= 0.0) and b is not equal to a whole number.

Parameters:: a - a double value.; b - a double value.
Returns:: the value a^b.
Throws: ArithmeticException: if (a == 0.0) and (b <= 0.0), or if (a <= 0.0) and b is not equal to a whole number.

round

 public static int round(float a)

Returns the closest int to the argument.

If the argument is negative infinity or any value less than or equal to the value of Integer.MIN_VALUE, the result is equal to the value of Integer.MIN_VALUE.

If the argument is positive infinity or any value greater than or equal to the value of Integer.MAX_VALUE, the result is equal to the value of Integer.MAX_VALUE.

Parameters:: a - a float value.
Returns:: the value of the argument rounded to the nearest int value.
See Also:: MAX_VALUE, MIN_VALUE

round

 public static long round(double a)

Returns the closest long to the argument.

If the argument is negative infinity or any value less than or equal to the value of Long.MIN_VALUE, the result is equal to the value of Long.MIN_VALUE.

If the argument is positive infinity or any value greater than or equal to the value of Long.MAX_VALUE, the result is equal to the value of Long.MAX_VALUE.

Parameters:: a - a double value.
Returns:: the value of the argument rounded to the nearest long value.
See Also:: MAX_VALUE, MIN_VALUE

random

 public static synchronized double random()

Returns a random number between 0.0 and 1.0. Random number generators are often referred to as pseudorandom number generators because the numbers produced tend to repeat themselves after a period of time.

Returns:: a pseudorandom double between 0.0 and 1.0.
See Also:: nextDouble

abs

 public static int abs(int a)

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 Integer.MIN_VALUE, the most negative representable int value, the result is that same value, which is negative.

Parameters:: a - an int value.
Returns:: the absolute value of the argument.
See Also:: MIN_VALUE

abs

 public static long abs(long a)

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 Long.MIN_VALUE, the most negative representable long value, the result is that same value, which is negative.

Parameters:: a - a long value.
Returns:: the absolute value of the argument.
See Also:: MIN_VALUE

abs

 public static float abs(float a)

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.

Parameters:: a - a float value.
Returns:: the absolute value of the argument.

abs

 public static double abs(double a)

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.

Parameters:: a - a double value.
Returns:: the absolute value of the argument.

max

 public static int max(int a,
                       int b)

Returns the greater of two int values.

Parameters:: a - an int value.; b - an int value.
Returns:: the larger of a and b.

max

 public static long max(long a,
                        long b)

Returns the greater of two long values.

Parameters:: a - a long value.; b - a long value.
Returns:: the larger of a and b.

max

 public static float max(float a,
                         float b)

Returns the greater of two float values. If either value is NaN, then the result is NaN. Unlike the the numerical comparison operators, this method considers negative zero to be strictly smaller than positive zero.

Parameters:: a - a float value.; b - a float value.
Returns:: the larger of a and b.

max

 public static double max(double a,
                          double b)

Returns the greater of two double values. If either value is NaN, then the result is NaN. Unlike the the numerical comparison operators, this method considers negative zero to be strictly smaller than positive zero.

Parameters:: a - a double value.; b - a double value.
Returns:: the larger of a and b.

min

 public static int min(int a,
                       int b)

Returns the smaller of two int values.

Parameters:: a - an int value.; b - an int value.
Returns:: the smaller of a and b.

min

 public static long min(long a,
                        long b)

Returns the smaller of two long values.

Parameters:: a - a long value.; b - a long value.
Returns:: the smaller of a and b.

min

 public static float min(float a,
                         float b)

Returns the smaller of two float values. If either value is NaN, then the result is NaN. Unlike the the numerical comparison operators, this method considers negative zero to be strictly smaller than positive zero.

Parameters:: a - a float value.; b - a float value.
Returns:: the smaller of a and b.

min

 public static double min(double a,
                          double b)

Returns the smaller of two double values. If either value is NaN, then the result is NaN. Unlike the the numerical comparison operators, this method considers negative zero to be strictly smaller than positive zero.

Parameters:: a - a double value.; b - a double value.
Returns:: the smaller of a and b.

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