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StrictMath (Java 2 Platform SE v1.4.1) - JDK 5 Documentation v1.4.1, Java 2 SDK 英文文档

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java.lang
Class StrictMath

java.lang.Object
  |
  +--java.lang.StrictMath
public final class StrictMath
extends Object

The class StrictMath 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:
1.3

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 y, double x)
          Converts rectangular coordinates (x, y) 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 Euler's number e 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 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 sin(double a)
          Returns the trigonometric sine of an angle.
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 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.
 
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.

See Also:
Constant Field Values

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.

See Also:
Constant Field Values
Method Detail

sin

public static double sin(double a)
Returns the trigonometric sine of an angle. Special cases:
  • If the argument is NaN or an infinity, then the result is NaN.
  • If the argument is zero, then the result is a zero with the same sign as the argument.

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

cos

public static double cos(double a)
Returns the trigonometric cosine of an angle. Special cases:
  • If the argument is NaN or an infinity, then the result is NaN.

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

tan

public static double tan(double a)
Returns the trigonometric tangent of an angle. Special cases:
  • If the argument is NaN or an infinity, then the result is NaN.
  • If the argument is zero, then the result is a zero with the same sign as the argument.

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

asin

public static double asin(double a)
Returns the arc sine of an angle, in the range of -pi/2 through pi/2. Special cases:
  • If the argument is NaN or its absolute value is greater than 1, then the result is NaN.
  • If the argument is zero, then the result is a zero with the same sign as the argument.

Parameters:
a - the value whose arc sine is to be returned.
Returns:
the arc sine of the argument.

acos

public static double acos(double a)
Returns the arc cosine of an angle, in the range of 0.0 through pi. Special case:
  • If the argument is NaN or its absolute value is greater than 1, then the result is NaN.

Parameters:
a - the value whose arc cosine is to be returned.
Returns:
the arc cosine of the argument.

atan

public static double atan(double a)
Returns the arc tangent of an angle, in the range of -pi/2 through pi/2. Special cases:
  • If the argument is NaN, then the result is NaN.
  • If the argument is zero, then the result is a zero with the same sign as the argument.

Parameters:
a - the value whose arc tangent is to be returned.
Returns:
the arc tangent of the argument.

toRadians

public static double toRadians(double angdeg)
Converts an angle measured in degrees to an approximately equivalent angle measured in radians. The conversion from degrees to radians is generally inexact.

Parameters:
angdeg - an angle, in degrees
Returns:
the measurement of the angle angdeg in radians.

toDegrees

public static double toDegrees(double angrad)
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.

Parameters:
angrad - an angle, in radians
Returns:
the measurement of the angle angrad in degrees.

exp

public static double exp(double a)
Returns Euler's number e raised to the power of a double value. Special cases:
  • If the argument is NaN, the result is NaN.
  • If the argument is positive infinity, then the result is positive infinity.
  • If the argument is negative infinity, then the result is positive zero.

Parameters:
a - the exponent to raise e to.
Returns:
the value ea, where e is the base of the natural logarithms.

log

public static double log(double a)
Returns the natural logarithm (base e) of a double value. Special cases:
  • If the argument is NaN or less than zero, then the result is NaN.
  • If the argument is positive infinity, then the result is positive infinity.
  • If the argument is positive zero or negative zero, then the result is negative infinity.

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

sqrt

public static double sqrt(double a)
Returns the correctly rounded positive square root of a double value. Special cases:
  • If the argument is NaN or less than zero, then the result is NaN.
  • If the argument is positive infinity, then the result is positive infinity.
  • If the argument is positive zero or negative zero, then the result is the same as the argument.
Otherwise, the result is the double value closest to the true mathematical square root of the argument value.

Parameters:
a - a value.
Returns:
the positive square root of a.

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. Special cases:
  • If either argument is NaN, or the first argument is infinite, or the second argument is positive zero or negative zero, then the result is NaN.
  • If the first argument is finite and the second argument is infinite, then the result is the same as the first argument.

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

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. Special cases:
  • If the argument value is already equal to a mathematical integer, then the result is the same as the argument.
  • If the argument is NaN or an infinity or positive zero or negative zero, then the result is the same as the argument.
  • If the argument value is less than zero but greater than -1.0, then the result is negative zero.
Note that the value of Math.ceil(x) is exactly the value of -Math.floor(-x).

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

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. Special cases:
  • If the argument value is already equal to a mathematical integer, then the result is the same as the argument.
  • If the argument is NaN or an infinity or positive zero or negative zero, then the result is the same as the argument.

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

rint

public static double rint(double a)
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 to the value of the argument, the result is the integer value that is even. Special cases:
  • If the argument value is already equal to a mathematical integer, then the result is the same as the argument.
  • If the argument is NaN or an infinity or positive zero or negative zero, then the result is the same as the argument.

Parameters:
a - a value.
Returns:
the closest floating-point value to a that is equal to a mathematical integer.

atan2

public static double atan2(double y,
                           double x)
Converts rectangular coordinates (x, y) to polar (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:
  • If either argument is NaN, then the result is NaN.
  • If the first argument is positive zero and the second argument is positive, or the first argument is positive and finite and the second argument is positive infinity, then the result is positive zero.
  • If the first argument is negative zero and the second argument is positive, or the first argument is negative and finite and the second argument is positive infinity, then the result is negative zero.
  • If the first argument is positive zero and the second argument is negative, or the first argument is positive and finite and the second argument is negative infinity, then the result is the double value closest to pi.
  • If the first argument is negative zero and the second argument is negative, or the first argument is negative and finite and the second argument is negative infinity, then the result is the double value closest to -pi.
  • If the first argument is positive and the second argument is positive zero or negative zero, or the first argument is positive infinity and the second argument is finite, then the result is the double value closest to pi/2.
  • If the first argument is negative and the second argument is positive zero or negative zero, or the first argument is negative infinity and the second argument is finite, then the result is the double value closest to -pi/2.
  • If both arguments are positive infinity, then the result is the double value closest to pi/4.
  • If the first argument is positive infinity and the second argument is negative infinity, then the result is the double value closest to 3*pi/4.
  • If the first argument is negative infinity and the second argument is positive infinity, then the result is the double value closest to -pi/4.
  • If both arguments are negative infinity, then the result is the double value closest to -3*pi/4.

Parameters:
y - the ordinate coordinate
x - the abscissa coordinate
Returns:
the theta component of the point (r, theta) in polar coordinates that corresponds to the point (x, y) in Cartesian coordinates.

pow

public static double pow(double a,
                         double b)
Returns of value of the first argument raised to the power of the second argument. Special cases:
  • If the second argument is positive or negative zero, then the result is 1.0.
  • If the second argument is 1.0, then the result is the same as the first argument.
  • If the second argument is NaN, then the result is NaN.
  • If the first argument is NaN and the second argument is nonzero, then the result is NaN.
  • If the absolute value of the first argument is greater than 1 and the second argument is positive infinity, or the absolute value of the first argument is less than 1 and the second argument is negative infinity, then the result is positive infinity.
  • If the absolute value of the first argument is greater than 1 and the second argument is negative infinity, or the absolute value of the first argument is less than 1 and the second argument is positive infinity, then the result is positive zero.
  • If the absolute value of the first argument equals 1 and the second argument is infinite, then the result is NaN.
  • If the first argument is positive zero and the second argument is greater than zero, or the first argument is positive infinity and the second argument is less than zero, then the result is positive zero.
  • If the first argument is positive zero and the second argument is less than zero, or the first argument is positive infinity and the second argument is greater than zero, then the result is positive infinity.
  • If the first argument is negative zero and the second argument is greater than zero but not a finite odd integer, or the first argument is negative infinity and the second argument is less than zero but not a finite odd integer, then the result is positive zero.
  • If the first argument is negative zero and the second argument is a positive finite odd integer, or the first argument is negative infinity and the second argument is a negative finite odd integer, then the result is negative zero.
  • If the first argument is negative zero and the second argument is less than zero but not a finite odd integer, or the first argument is negative infinity and the second argument is greater than zero but not a finite odd integer, then the result is positive infinity.
  • If the first argument is negative zero and the second argument is a negative finite odd integer, or the first argument is negative infinity and the second argument is a positive finite odd integer, then the result is negative infinity.
  • If the first argument is less than zero and the second argument is a finite even integer, then the result is equal to the result of raising the absolute value of the first argument to the power of the second argument.
  • If the first argument is less than zero and the second argument is a finite odd integer, then the result is equal to the negative of the result of raising the absolute value of the first argument to the power of the second argument.
  • If the first argument is finite and less than zero and the second argument is finite and not an integer, then the result is NaN.
  • If both arguments are integers, then the result is exactly equal to the mathematical result of raising the first argument to the power of the second argument if that result can in fact be represented exactly as a double value.

(In the foregoing descriptions, a floating-point value is considered to be an integer if and only if it is 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.)

Parameters:
a - base.
b - the exponent.
Returns:
the value ab.

round

public static int round(float a)
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:

  • If the argument is NaN, the result is 0.
  • 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 floating-point value to be rounded to an integer.
Returns:
the value of the argument rounded to the nearest int value.
See Also:
Integer.MAX_VALUE, Integer.MIN_VALUE

round

public static long round(double a)
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:

  • If the argument is NaN, the result is 0.
  • 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 floating-point value to be rounded to a long.
Returns:
the value of the argument rounded to the nearest long value.
See Also:
Long.MAX_VALUE, Long.MIN_VALUE

random

public static double random()
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 

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()

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 - the argument whose absolute value is to be determined.
Returns:
the absolute value of the argument.
See Also:
Integer.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 - the argument whose absolute value is to be determined.
Returns:
the absolute value of the argument.
See Also:
Long.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. Special cases:
  • If the argument is positive zero or negative zero, the result is positive zero.
  • If the argument is infinite, the result is positive infinity.
  • If the argument is NaN, the result is NaN.
In other words, the result is the same as the value of the expression: 

Float.intBitsToFloat(0x7fffffff & Float.floatToIntBits(a))

Parameters:
a - the argument whose absolute value is to be determined
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. Special cases:
  • If the argument is positive zero or negative zero, the result is positive zero.
  • If the argument is infinite, the result is positive infinity.
  • If the argument is NaN, the result is NaN.
In other words, the result is the same as the value of the expression:

Double.longBitsToDouble((Double.doubleToLongBits(a)<<1)>>>1)

Parameters:
a - the argument whose absolute value is to be determined
Returns:
the absolute value of the argument.

max

public static int max(int a,
                      int b)
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.

Parameters:
a - an argument.
b - another argument.
Returns:
the larger of a and b.
See Also:
Long.MAX_VALUE

max

public static long max(long a,
                       long b)
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.

Parameters:
a - an argument.
b - another argument.
Returns:
the larger of a and b.
See Also:
Long.MAX_VALUE

max

public static float max(float a,
                        float b)
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 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.

Parameters:
a - an argument.
b - another argument.
Returns:
the larger of a and b.

max

public static double max(double a,
                         double b)
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 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.

Parameters:
a - an argument.
b - another argument.
Returns:
the larger of a and b.

min

public static int min(int a,
                      int b)
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.

Parameters:
a - an argument.
b - another argument.
Returns:
the smaller of a and b.
See Also:
Long.MIN_VALUE

min

public static long min(long a,
                       long b)
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.

Parameters:
a - an argument.
b - another argument.
Returns:
the smaller of a and b.
See Also:
Long.MIN_VALUE

min

public static float min(float a,
                        float b)
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 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.

Parameters:
a - an argument.
b - another argument.
Returns:
the smaller of a and b.

min

public static double min(double a,
                         double b)
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 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.

Parameters:
a - an argument.
b - another argument.
Returns:
the smaller of a and b.
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JavaTM 2 Platform
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For further API reference and developer documentation, see Java 2 SDK SE Developer Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.

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