org.apache.commons.math3.util

Class MathUtils

java.lang.Object

org.apache.commons.math3.util.MathUtils

public final class MathUtils
extends java.lang.Object

Miscellaneous utility functions.

See Also:

ArithmeticUtils, Precision, MathArrays

Field Summary

Fields

Modifier and Type	Field and Description
static double	PI_SQUARED \(\pi^2\)
static double	TWO_PI \(2\pi\)

Method Summary

Modifier and Type	Method and Description
static void	checkFinite(double x) Check that the argument is a real number.
static void	checkFinite(double[] val) Check that all the elements are real numbers.
static void	checkNotNull(java.lang.Object o) Checks that an object is not null.
static void	checkNotNull(java.lang.Object o, Localizable pattern, java.lang.Object... args) Checks that an object is not null.
static byte	copySign(byte magnitude, byte sign) Returns the first argument with the sign of the second argument.
static int	copySign(int magnitude, int sign) Returns the first argument with the sign of the second argument.
static long	copySign(long magnitude, long sign) Returns the first argument with the sign of the second argument.
static short	copySign(short magnitude, short sign) Returns the first argument with the sign of the second argument.
static boolean	equals(double x, double y) Returns true if the values are equal according to semantics of Double.equals(Object).
static int	hash(double value) Returns an integer hash code representing the given double value.
static int	hash(double[] value) Returns an integer hash code representing the given double array.
static <T extends RealFieldElement<T>> T	max(T e1, T e2) Find the maximum of two field elements.
static <T extends RealFieldElement<T>> T	min(T e1, T e2) Find the minimum of two field elements.
static double	normalizeAngle(double a, double center) Normalize an angle in a 2π wide interval around a center value.
static double	reduce(double a, double period, double offset) Reduce |a - offset| to the primary interval [0, |period|).

Methods inherited from class java.lang.Object

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

Field Detail

TWO_PI

public static final double TWO_PI

\(2\pi\)

Since:

2.1

See Also:

Constant Field Values

PI_SQUARED

public static final double PI_SQUARED

\(\pi^2\)

Since:

3.4

See Also:

Constant Field Values

Method Detail

hash

public static int hash(double value)

Returns an integer hash code representing the given double value.

Parameters:

value - the value to be hashed

Returns:

the hash code

equals

public static boolean equals(double x,
                             double y)

Returns true if the values are equal according to semantics of Double.equals(Object).

Parameters:

x - Value

y - Value

Returns:

new Double(x).equals(new Double(y))

hash

public static int hash(double[] value)

Returns an integer hash code representing the given double array.

Parameters:

value - the value to be hashed (may be null)

Returns:

the hash code

Since:

1.2

normalizeAngle

public static double normalizeAngle(double a,
                                    double center)

Normalize an angle in a 2π wide interval around a center value.

This method has three main uses:

• normalize an angle between 0 and 2π:
  a = MathUtils.normalizeAngle(a, FastMath.PI);
• normalize an angle between -π and +π
  a = MathUtils.normalizeAngle(a, 0.0);
• compute the angle between two defining angular positions:
  angle = MathUtils.normalizeAngle(end, start) - start;

Note that due to numerical accuracy and since π cannot be represented exactly, the result interval is closed, it cannot be half-closed as would be more satisfactory in a purely mathematical view.

Parameters:

a - angle to normalize

center - center of the desired 2π interval for the result

Returns:

a-2kπ with integer k and center-π <= a-2kπ <= center+π

Since:

1.2

max

public static <T extends RealFieldElement<T>> T max(T e1,
                                                    T e2)

Find the maximum of two field elements.

Type Parameters:

T - the type of the field elements

Parameters:

e1 - first element

e2 - second element

Returns:

max(a1, e2)

Since:

3.6

min

public static <T extends RealFieldElement<T>> T min(T e1,
                                                    T e2)

Find the minimum of two field elements.

Type Parameters:

T - the type of the field elements

Parameters:

e1 - first element

e2 - second element

Returns:

min(a1, e2)

Since:

3.6

reduce

public static double reduce(double a,
                            double period,
                            double offset)

Reduce |a - offset| to the primary interval [0, |period|).

Specifically, the value returned is
a - |period| * floor((a - offset) / |period|) - offset.

If any of the parameters are NaN or infinite, the result is NaN.

Parameters:

a - Value to reduce.

period - Period.

offset - Value that will be mapped to 0.

Returns:

the value, within the interval [0 |period|), that corresponds to a.

copySign

public static byte copySign(byte magnitude,
                            byte sign)
                     throws MathArithmeticException

Returns the first argument with the sign of the second argument.

Parameters:

magnitude - Magnitude of the returned value.

sign - Sign of the returned value.

Returns:

a value with magnitude equal to magnitude and with the same sign as the sign argument.

Throws:

MathArithmeticException - if magnitude == Byte.MIN_VALUE and sign >= 0.

copySign

public static short copySign(short magnitude,
                             short sign)
                      throws MathArithmeticException

Returns the first argument with the sign of the second argument.

Parameters:

magnitude - Magnitude of the returned value.

sign - Sign of the returned value.

Returns:

a value with magnitude equal to magnitude and with the same sign as the sign argument.

Throws:

MathArithmeticException - if magnitude == Short.MIN_VALUE and sign >= 0.

copySign

public static int copySign(int magnitude,
                           int sign)
                    throws MathArithmeticException

Returns the first argument with the sign of the second argument.

Parameters:

magnitude - Magnitude of the returned value.

sign - Sign of the returned value.

Returns:

a value with magnitude equal to magnitude and with the same sign as the sign argument.

Throws:

MathArithmeticException - if magnitude == Integer.MIN_VALUE and sign >= 0.

copySign

public static long copySign(long magnitude,
                            long sign)
                     throws MathArithmeticException

Returns the first argument with the sign of the second argument.

Parameters:

magnitude - Magnitude of the returned value.

sign - Sign of the returned value.

Returns:

a value with magnitude equal to magnitude and with the same sign as the sign argument.

Throws:

MathArithmeticException - if magnitude == Long.MIN_VALUE and sign >= 0.

checkFinite

public static void checkFinite(double x)
                        throws NotFiniteNumberException

Check that the argument is a real number.

Parameters:

x - Argument.

Throws:

NotFiniteNumberException - if x is not a finite real number.

checkFinite

public static void checkFinite(double[] val)
                        throws NotFiniteNumberException

Check that all the elements are real numbers.

Parameters:

val - Arguments.

Throws:

NotFiniteNumberException - if any values of the array is not a finite real number.

checkNotNull

public static void checkNotNull(java.lang.Object o,
                                Localizable pattern,
                                java.lang.Object... args)
                         throws NullArgumentException

Checks that an object is not null.

Parameters:

o - Object to be checked.

pattern - Message pattern.

args - Arguments to replace the placeholders in pattern.

Throws:

NullArgumentException - if o is null.

checkNotNull

public static void checkNotNull(java.lang.Object o)
                         throws NullArgumentException

Checks that an object is not null.

Parameters:

o - Object to be checked.

Throws:

NullArgumentException - if o is null.