com.bigdata.util

Class PseudoRandom

java.lang.Object

com.bigdata.util.PseudoRandom

public class PseudoRandom
extends Object

PseudoRandom is derived from an algorithm used to create a dissolve graphics effect. Given a maximum number it generates all numbers from 1 to that number in a deterministic but pseudorandom order. It is therefore particularly useful for test cases. See: http://www.mactech.com/articles/mactech/Vol.06/06.12/SafeDissolve/index.html

Constructor Summary

Constructors

Constructor and Description
PseudoRandom(int range) Create a pseudo random number generator which will visit each integer in a half-open range.
PseudoRandom(int range, int next) Create a pseudo random number generator which will visit each integer in a half-open range.

Method Summary

Methods

Modifier and Type	Method and Description
int	next()
int	next(int prev) Reset the pseudo random generator to a state where it has just visited prev.
void	nextBytes(byte[] key)
void	nextBytes(byte[] key, int prev)
int	nextInt(int range) The next number modulo the range.

Methods inherited from class java.lang.Object

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

Constructor Detail

PseudoRandom

public PseudoRandom(int range,
            int next)

Create a pseudo random number generator which will visit each integer in a half-open range.

Parameters:

range - The exclusive upper bound of the half-open range (0:range].

next - The next number to visit in (0:range].

PseudoRandom

public PseudoRandom(int range)

Create a pseudo random number generator which will visit each integer in a half-open range. The first visited value will be 1.

Parameters:

range - The exclusive upper bound of the half-open range (0:range].

Method Detail

next

public int next()

nextInt

public int nextInt(int range)

The next number modulo the range.

Parameters:

range - The range.

Returns:

The number.

Throws:

IllegalArgumentException - if the range is negative.

IllegalStateException - if the range is greater than the range specified to the constructor (ie., the generated could not produce all numbers in the given range).

next

public int next(int prev)

Reset the pseudo random generator to a state where it has just visited prev.

Parameters:

prev - The "previous" value.

Returns:

The next value in the pseudo random sequence after prev.

nextBytes

public void nextBytes(byte[] key,
             int prev)

nextBytes

public void nextBytes(byte[] key)