com.unboundid.util.ThreadLocalRandom Maven / Gradle / Ivy
/*
* Copyright 2014-2019 Ping Identity Corporation
* All Rights Reserved.
*/
/*
* Copyright (C) 2014-2019 Ping Identity Corporation
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License (GPLv2 only)
* or the terms of the GNU Lesser General Public License (LGPLv2.1 only)
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, see .
*/
package com.unboundid.util;
import java.util.Random;
/**
* This class provides a means of obtaining a thread-local random number
* generator that can be used by the current thread without the need for
* synchronization.
*/
@ThreadSafety(level=ThreadSafetyLevel.COMPLETELY_THREADSAFE)
public final class ThreadLocalRandom
{
/**
* The random number generator that will be used to seed per-thread instances.
*/
private static final Random SEED_RANDOM = new Random();
/**
* The thread-local instances that have been created.
*/
private static final ThreadLocal INSTANCES = new ThreadLocal<>();
/**
* Prevents this class from being instantiated.
*/
private ThreadLocalRandom()
{
// No implementation required.
}
/**
* Gets a thread-local random number generator instance.
*
* @return A thread-local random number generator instance.
*/
public static Random get()
{
Random r = INSTANCES.get();
if (r == null)
{
final long seed;
synchronized (SEED_RANDOM)
{
seed = SEED_RANDOM.nextLong();
}
r = new Random(seed);
INSTANCES.set(r);
}
return r;
}
}