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The UnboundID LDAP SDK for Java is a fast, comprehensive, and easy-to-use Java API for communicating with LDAP directory servers and performing related tasks like reading and writing LDIF, encoding and decoding data using base64 and ASN.1 BER, and performing secure communication. This package contains the Standard Edition of the LDAP SDK, which is a complete, general-purpose library for communicating with LDAPv3 directory servers.

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/*
 * Copyright 2014-2018 Ping Identity Corporation
 * All Rights Reserved.
 */
/*
 * Copyright (C) 2014-2018 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;
  }
}