dk.rode.thesis.facade
Class MathFacade

java.lang.Object
  dk.rode.thesis.facade.MathFacade

@Participant(value="Facade")
public class MathFacade
extends Object

A math facade is a small math library that represents an-easy-to-use high-level interface for complex mathematical functions. (yeah, right...)

Facade usage is thread-safe.

Implementation notes:
The small examples used throughout this thesis does not really justify use of Facade; they are simply not complex enough. Still, this Facade implementation address several issues discussed by Gamma et al. [Gamma95, p.185-193]:

• The mathematical functions implemented with sequences are too verbose and tedious to be implemented by any client, and hence this facade help provide the desired functionality, shielding clients from the gory details.

• The facade shield the client from knowing about specific sub-system classes, i.e. sequences.

• The facade implementation use package private access to ensure certain sub-system classes are off-limit from clients.

• The facade is implemented as a Singleton.

Author:

Gunni Rode / rode.dk

Field Summary

private Map<Integer,AckermannSequence>	ackermann A map storing calculated Ackermann values, A(m,n), per m value.
private static MathFacade	instance The singleton instance to use.
private ReversiblePrimeSequence	primes The prime sequence to deliver the prime numbers.
private UnboundedRandomSequence	random An unbounded random sequence that uses a Fibonacci sequence as the seed.

Constructor Summary

private

MathFacade() Private constructor as this class is a singleton.

Method Summary

int	getAckermannNumber(int m, int n) Returns the value of the Ackermann function, A(m,n), for m and n values supplied as m and n, respectively.
static MathFacade	getInstance() Returns the math library to use.
BigInteger	getNthFibonnaciNumber(int n) Returns the n'th Fibonacci number.
int	getNthPrimeNumber(int n) Returns the n'th prime number.
boolean	getRandomBoolean() Returns a pseudo random boolean value.
BigInteger	getRandomFibonnaciNumber(int n) Returns a random Fibonacci number between the first and the n'th number.
long	getRandomNumber() Returns a random number.
int	getRandomNumber(int highBound) Return a pseudo random number between one and highBound.
int	getRandomNumber(int lowBound, int highBound) Return a pseudo random number between lowBound and highBound.
int	getRandomPrimeNumber(int n) Returns a random prime number between the first and the n'th prime number.
String	toString() Return the string representation of this facade.

Methods inherited from class java.lang.Object

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

Field Detail

ackermann

private Map<Integer,AckermannSequence> ackermann

A map storing calculated Ackermann values, A(m,n), per m value.

Never null.

instance

private static final MathFacade instance

The singleton instance to use.

Never null.

primes

@ParticipantUsage(value="SubsystemClass",
                  type=ReversiblePrimeSequence.class)
private ReversiblePrimeSequence primes

The prime sequence to deliver the prime numbers.

Will "grow in size" as needed.

Lazily created.

random

private final UnboundedRandomSequence random

An unbounded random sequence that uses a Fibonacci sequence as the seed.

Never null.

Constructor Detail

MathFacade

private MathFacade()

Private constructor as this class is a singleton.

Method Detail

getAckermannNumber

public int getAckermannNumber(int m,
                              int n)

Returns the value of the Ackermann function, A(m,n), for m and n values supplied as m and n, respectively.

Parameters:

m - The m value for the Ackermann function; cannot be negative.

n - The n value for the Ackermann function; cannot be negative.

Returns:

The A(m,n) value.

Throws:

IllegalArgumentException - If m or n are illegal.

getInstance

public static final MathFacade getInstance()

Returns the math library to use.

Returns:

The math library; never null.

getNthFibonnaciNumber

public BigInteger getNthFibonnaciNumber(int n)

Returns the n'th Fibonacci number.

Parameters:

n - Identifies the Fibonacci number to return; cannot be smaller than one.

Returns:

The n'th Fibonacci number.

Throws:

IllegalArgumentException - If n is smaller than one.

getNthPrimeNumber

public int getNthPrimeNumber(int n)

Returns the n'th prime number.

Parameters:

n - Identifies the prime number to return; cannot be smaller than one.

Returns:

The n'th prime number.

Throws:

IllegalArgumentException - If n is smaller than one.

getRandomBoolean

public boolean getRandomBoolean()

Returns a pseudo random boolean value.

Returns:

True or false.

getRandomFibonnaciNumber

public BigInteger getRandomFibonnaciNumber(int n)

Returns a random Fibonacci number between the first and the n'th number.

Parameters:

n - The maximum number to return; cannot be smaller than one.

Returns:

A random Fibonacci number between the first and the n'th number.

Throws:

IllegalArgumentException - If n is smaller than one.

getRandomNumber

public long getRandomNumber()

Returns a random number.

Returns:

A random number.

getRandomNumber

public int getRandomNumber(int highBound)

Return a pseudo random number between one and highBound.

Parameters:

highBound - The high bound.

Returns:

The pseudo random number.

Throws:

IllegalArgumentException - If highBound is smaller than one.

getRandomNumber

public int getRandomNumber(int lowBound,
                           int highBound)

Return a pseudo random number between lowBound and highBound.

Parameters:

lowBound - The low bound.

highBound - The high bound.

Returns:

The pseudo random number.

Throws:

IllegalArgumentException - If highBound is smaller than lowBound.

getRandomPrimeNumber

public int getRandomPrimeNumber(int n)

Returns a random prime number between the first and the n'th prime number.

Parameters:

n - The maximum number to return; cannot be smaller than one.

Returns:

A random prime number between the first and the n'th prime number.

Throws:

IllegalArgumentException - If n is smaller than one.

toString

public String toString()

Return the string representation of this facade.

Overrides:

toString in class Object

Returns:

The string representation; never null.