org.josef.science.math

Class PrimeFactor

java.lang.Object

org.josef.science.math.PrimeFactor

@Status(stage=PRODUCTION,
        unitTests=COMPLETE)
 @Review(by="Kees Schotanus",
        at="2009-10-16",
        reason="Initial review")
 @ThreadSafety(level=IMMUTABLE)
public final class PrimeFactor
extends Object

A prime factor.
A prime factor is the result of prime factorization and is described by a prime number and an exponent. For example: The prime factors of 100 are: 2^2 and 5^2. How do you compute the prime factors of a number? "Simply" divide by all prime numbers up to the number to factorize. The problem is that it is computationally expensive to generate large prime numbers in sequence. This is why the factorize(...) methods in this class all use some optimization. They first determine whether 2 is a factor of the supplied value and then in a loop determine whether 3,5,7,9,11,13,... are factors. The loop ends when the factor is larger than the square root of the supplied value.
Note: Calculating prime factors of large numbers is very time consuming and calculating with BigIntegers is much more expensive than calculating with long values!
For a technical background on WikiPedia, click <a href="http://en.wikipedia.org/wiki/Prime_factor">here</a>.

Version:

1.0 $Revision: 6488 $

Author:

Kees Schotanus

Method Summary

Modifier and Type	Method and Description
static List<PrimeFactor>	factorize(BigInteger value) Factorizes the supplied BigInteger value into its prime factors.
static List<PrimeFactor>	factorize(long value) Factorizes the supplied long value into its prime factors.
int	getExponent() Gets the exponent of this PrimeFactor.
BigInteger	getPrimeNumber() Gets the prime number of this PrimeFactor.
String	toString() Creates a String representation of this PrimeFactor.

Methods inherited from class java.lang.Object

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

Method Detail

getPrimeNumber

public BigInteger getPrimeNumber()

Gets the prime number of this PrimeFactor.

Returns:

The prime number of this PrimeFactor.

getExponent

public int getExponent()

Gets the exponent of this PrimeFactor.

Returns:

The exponent of this PrimeFactor.

factorize

public static List<PrimeFactor> factorize(BigInteger value)

Factorizes the supplied BigInteger value into its prime factors.
For numbers smaller than Long.MAX_VALUE you are better of using factorize(long).

Parameters:

value - The value to factorize.

Returns:

A list of prime factors.

Throws:

ArithmeticException - When the supplied value is < 2.

NullPointerException - When the supplied value is null.

factorize

public static List<PrimeFactor> factorize(long value)

Factorizes the supplied long value into its prime factors.

Parameters:

value - The value to factorize.

Returns:

A list of prime factors.

Throws:

ArithmeticException - When the supplied value is < 2.

NullPointerException - When the supplied value is null.

toString

public String toString()

Creates a String representation of this PrimeFactor.

Overrides:

toString in class Object

Returns:

A String representation of this PrimeFactor.