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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 2009-2024 Ping Identity Corporation
 * All Rights Reserved.
 */
/*
 * Copyright 2009-2024 Ping Identity Corporation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/*
 * Copyright (C) 2009-2024 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.io.Serializable;
import java.util.Comparator;



/**
 * This class provides an implementation of a {@code Comparator} object that may
 * be used to iterate through values in what would normally be considered
 * reverse order.
 *
 * @param    The type of object to use with this comparator.
 */
@NotMutable()
@ThreadSafety(level=ThreadSafetyLevel.COMPLETELY_THREADSAFE)
public final class ReverseComparator
       implements Comparator, Serializable
{
  /**
   * The serial version UID for this serializable class.
   */
  private static final long serialVersionUID = -4615537960027681276L;



  // The comparator that will be used to make the underlying determination.
  @Nullable private final Comparator baseComparator;



  /**
   * Creates a new comparator that will sort items in reverse order.  The
   * generic type for this class must implement the {@link Comparable}
   * interface.
   */
  public ReverseComparator()
  {
    baseComparator = null;
  }



  /**
   * Creates a new comparator that will sort items in the reverse order that
   * they would be normally sorted using the given comparator.
   *
   * @param  baseComparator  The base comparator that will be used to make the
   *                         determination.
   */
  public ReverseComparator(@NotNull final Comparator baseComparator)
  {
    this.baseComparator = baseComparator;
  }



  /**
   * Compares the provided objects to determine their relative order in a
   * sorted list.
   *
   * @param  o1  The first object to compare.
   * @param  o2  The second object to compare.
   *
   * @return  A negative integer if the first object should be ordered before
   *          the second, a positive integer if the first object should be
   *          ordered after the second, or zero if there is no difference in
   *          their relative orders.
   */
  @SuppressWarnings("unchecked")
  @Override()
  public int compare(@NotNull final T o1, @NotNull final T o2)
  {
    final int baseValue;
    if (baseComparator == null)
    {
      baseValue = ((Comparable) o1).compareTo(o2);
    }
    else
    {
      baseValue = baseComparator.compare(o1, o2);
    }

    if (baseValue < 0)
    {
      return 1;
    }
    else if (baseValue > 0)
    {
      return -1;
    }
    else
    {
      return 0;
    }
  }



  /**
   * Retrieves a hash code for this class.
   *
   * @return  A hash code for this class.
   */
  @Override()
  public int hashCode()
  {
    if (baseComparator == null)
    {
      return 0;
    }
    else
    {
      return baseComparator.hashCode();
    }
  }



  /**
   * Indicates whether the provided object may be considered equal to this
   * comparator.
   *
   * @param  o  The object for which to make the determination.
   *
   * @return  {@code true} if the provided object may be considered equal to
   *          this comparator, or {@code false} if not.
   */
  @Override()
  @SuppressWarnings("unchecked")
  public boolean equals(@Nullable final Object o)
  {
    if (o == null)
    {
      return false;
    }

    if (o == this)
    {
      return true;
    }

    if (! (o.getClass().equals(ReverseComparator.class)))
    {
      return false;
    }

    final ReverseComparator c = (ReverseComparator) o;
    if (baseComparator == null)
    {
      return (c.baseComparator == null);
    }
    else
    {
      return baseComparator.equals(c.baseComparator);
    }
  }
}