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Java(TM) 2 Platform, Standard Edition, v1.2.2 API Specification: Class Math - JDK 5 Documentation v1.2.2, Java 2 SDK 英文文档

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java.lang
Class Math

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

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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://metalab.unc.edu/
 

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).

Since:

JDK1.0

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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 an angle, in the range of 0.0 through pi.
static double	asin(double a)           Returns the arc sine of an angle, in the range of -pi/2 through pi/2.
static double	atan(double a)           Returns the arc tangent of an angle, in the range of -pi/2 through pi/2.
static double	atan2(double a, double b)           Converts rectangular coordinates (b, a) to polar (r, theta).
static 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.
static double	cos(double a)           Returns the trigonometric cosine of an angle.
static double	exp(double a)           Returns the exponential number e (i.e., 2.718...) raised to the power of a double value.
static 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.
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	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	pow(double a, double b)           Returns of value of the first argument raised to the power of the second argument.
static double	random()           Returns a random number greater than or equal to 0.0 and less than 1.0.
static double	rint(double a)           returns the closest integer to the argument.
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	sin(double a)           Returns the trigonometric sine of an angle.
static double	sqrt(double a)           Returns the square root of a double value.
static double	tan(double a)           Returns the trigonometric tangent of an angle.
static double	toDegrees(double angrad)           Converts an angle measured in radians to the equivalent angle measured in degrees.
static double	toRadians(double angdeg)           Converts an angle measured in degrees to the equivalent angle measured in radians.

 

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

 

Field Detail

E

public static final double E

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

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PI

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.

Method Detail

sin

public static double sin(double a)

Returns the trigonometric sine of an angle.

Parameters:

a - an angle, in radians.

Returns:

the sine of the argument.

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cos

public static double cos(double a)

Returns the trigonometric cosine of an angle.

Parameters:

a - an angle, in radians.

Returns:

the cosine of the argument.

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tan

public static double tan(double a)

Returns the trigonometric tangent of an angle.

Parameters:

a - an angle, in radians.

Returns:

the tangent of the argument.

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asin

public static double asin(double a)

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

Parameters:

a - the double value whose arc sine is to be returned.

Returns:

the arc sine of the argument.

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acos

public static double acos(double a)

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

Parameters:

a - the double value whose arc cosine is to be returned.

Returns:

the arc cosine of the argument.

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atan

public static double atan(double a)

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

Parameters:

a - the double value whose arc tangent is to be returned.

Returns:

the arc tangent of the argument.

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toRadians

public static double toRadians(double angdeg)

Converts an angle measured in degrees to the equivalent angle measured in radians.

Parameters:

angdeg - an angle, in degrees

Returns:

the measurement of the angle angdeg in radians.

Since:

JDK1.2

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toDegrees

public static double toDegrees(double angrad)

Converts an angle measured in radians to the equivalent angle measured in degrees.

Parameters:

angrad - an angle, in radians

Returns:

the measurement of the angle angrad in degrees.

Since:

JDK1.2

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exp

public static 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.

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log

public static 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.

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sqrt

public static 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.

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IEEEremainder

public static 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.

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ceil

public static 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.

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floor

public static 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.

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rint

public static 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.

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atan2

public static 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 a/b 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.

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pow

public static 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 ab.

Throws:

ArithmeticException - if (a == 0.0) and (b <= 0.0), or if (a <= 0.0) and b is not equal to a whole number.

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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:

Integer.MAX_VALUE, Integer.MIN_VALUE

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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:

Long.MAX_VALUE, Long.MIN_VALUE

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random

public static double random()

Returns a random number 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.

Returns:

a pseudorandom double greater than or equal to 0.0 and less than 1.0.

See Also:

Random.nextDouble()

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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:

Integer.MIN_VALUE

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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:

Long.MIN_VALUE

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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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