Package io.github.cjstehno.testthings.rando

Class SharedRandom

java.lang.Object

io.github.cjstehno.testthings.rando.SharedRandom

All Implemented Interfaces:

RandomGenerator

public class SharedRandom
extends Object
implements RandomGenerator

A thread-safe "random" number generated similar to the ThreadLocalRandom, but with the ability to have its seed changed after construction. The ability to know and change the seed at runtime is very useful in allowing for repeatable testing of "random"-based utilities. If you use the same seed, the same values will be generated in the same order. The seed may be injected programmatically, or a system property may be set ("test-tings.rando.seed") which will specify the seed for the whole JVM. NOTE: Setting the seed to a known value should ONLY be used for development and testing purposes.

Nested Class Summary

Nested classes/interfaces inherited from interface java.util.random.RandomGenerator

RandomGenerator.ArbitrarilyJumpableGenerator, RandomGenerator.JumpableGenerator, RandomGenerator.LeapableGenerator, RandomGenerator.SplittableGenerator, RandomGenerator.StreamableGenerator

Field Summary

Fields

Modifier and Type	Field	Description
static final String	SEED_PROPERTY	The System property which may be used to specify a custom seed value (e.g "test-things.rando.seed").

Method Summary

Modifier and Type	Method	Description
static RandomGenerator	current()	Retrieves the singleton instance of the RandomGenerator for the current thread.
static SharedRandom	generator()	Builds a SharedRandom with the default seed.
static SharedRandom	generator(Long seed)	Builds a SharedRandom with the specified seed.
long	nextLong()
void	reseed(long newSeed)	Updates the seed value and rebuilds the internal random generator.

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.random.RandomGenerator

doubles, doubles, doubles, doubles, ints, ints, ints, ints, isDeprecated, longs, longs, longs, longs, nextBoolean, nextBytes, nextDouble, nextDouble, nextDouble, nextExponential, nextFloat, nextFloat, nextFloat, nextGaussian, nextGaussian, nextInt, nextInt, nextInt, nextLong, nextLong

Field Details

SEED_PROPERTY

public static final String SEED_PROPERTY

The System property which may be used to specify a custom seed value (e.g "test-things.rando.seed").

See Also:

• Constant Field Values

Method Details

current

public static RandomGenerator current()

Retrieves the singleton instance of the RandomGenerator for the current thread.

Returns:

the random generator instance

nextLong

public long nextLong()

Specified by:

nextLong in interface RandomGenerator

reseed

public void reseed(long newSeed)

Updates the seed value and rebuilds the internal random generator.

Parameters:

newSeed - the new seed value

generator

public static SharedRandom generator(Long seed)

Builds a SharedRandom with the specified seed.

Parameters:

seed - the seed

Returns:

the SharedRandom instance

generator

public static SharedRandom generator()

Builds a SharedRandom with the default seed.

Returns:

the SharedRandom instance