Package com.irurueta.numerical

Class LongFactorialEstimator

java.lang.Object

com.irurueta.numerical.LongFactorialEstimator

public class LongFactorialEstimator
extends Object

Estimates factorial values as long integer values.

Field Summary

Fields

Modifier and Type	Field	Description
private final long[]	cache	Cache of values.
static final int	CACHE_SIZE	Cache size for factorial values that can be represented without overflowing with long precision.

Constructor Summary

Constructors

Constructor	Description
LongFactorialEstimator()	Constructor with default cache size.
LongFactorialEstimator(int cacheSize)	Constructor.

Method Summary

Modifier and Type	Method	Description
long	factorial(int value)	Gets factorial of provided value represented with double precision.
int	getCacheSize()	Gets current cache size.

Methods inherited from class java.lang.Object

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

Field Details

CACHE_SIZE

public static final int CACHE_SIZE

Cache size for factorial values that can be represented without overflowing with long precision. Values up to 20! are representable, 21! overflows.

See Also:

• Constant Field Values

cache

private final long[] cache

Cache of values.

Constructor Details

LongFactorialEstimator

public LongFactorialEstimator()

Constructor with default cache size.

LongFactorialEstimator

public LongFactorialEstimator(int cacheSize)

Constructor.

Parameters:

cacheSize - size of cache.

Throws:

IllegalArgumentException - if provided value is less than 1 or exceeds 21.

Method Details

getCacheSize

public int getCacheSize()

Gets current cache size.

Returns:

cache size.

factorial

public long factorial(int value)

Gets factorial of provided value represented with double precision.

Parameters:

value - value to compute factorial for.

Returns:

computed factorial value.

Throws:

IllegalArgumentException - if provided value exceeds cache size.