# BasicSorter.java

    /*
    ** Module   : BasicSorter.java
    ** Abstract : Directional comparator for Comparables
    **
    ** Copyright (c) 2004-2017, Golden Code Development Corporation.
    **
    ** -#- -I- --Date-- -T- --JPRM-- ----------------Description-----------------
    ** 001 ECF 20080708 ADD  @39078  Created initial version. Abstracted as a base
    **                               class from DataSorter. Needed to handle non-
    **                               BaseDataType Comparables.
    */
    /*
    ** This program is free software: you can redistribute it and/or modify
    ** it under the terms of the GNU Affero General Public License as
    ** published by the Free Software Foundation, either version 3 of the
    ** License, or (at your option) any later version.
    **
    ** 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 Affero General Public License for more details.
    **
    ** You may find a copy of the GNU Affero GPL version 3 at the following
    ** location: https://www.gnu.org/licenses/agpl-3.0.en.html
    **
    ** Additional terms under GNU Affero GPL version 3 section 7:
    **
    **   Under Section 7 of the GNU Affero GPL version 3, the following additional
    **   terms apply to the works covered under the License.  These additional terms
    **   are non-permissive additional terms allowed under Section 7 of the GNU
    **   Affero GPL version 3 and may not be removed by you.
    **
    **   0. Attribution Requirement.
    **
    **     You must preserve all legal notices or author attributions in the covered
    **     work or Appropriate Legal Notices displayed by works containing the covered
    **     work.  You may not remove from the covered work any author or developer
    **     credit already included within the covered work.
    **
    **   1. No License To Use Trademarks.
    **
    **     This license does not grant any license or rights to use the trademarks
    **     Golden Code, FWD, any Golden Code or FWD logo, or any other trademarks
    **     of Golden Code Development Corporation. You are not authorized to use the
    **     name Golden Code, FWD, or the names of any author or contributor, for
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    **
    **     You may not represent the covered work as solely your work.  All modified
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    **     attribution required in this license.
    */

    package com.goldencode.p2j.persist;

    import java.io.*;
    import java.util.*;

    /**
     * An implementation of <code>Comparator</code>, used to sort instances of
     * <code>Comparable</code>s in ascending or descending order.  Direction of
     * the sort is specified upon construction.
     *
     * @param   <T>
     *          A type which extends/implements Comparable
     */
    public class BasicSorter<T extends Comparable>
    implements Comparator<T>,
               Serializable
    {
       /** Multiplier used to adjust (possibly invert) sorting */
       private final int direction;

       /**
        * Constructor which stores the sort direction.
        *
        * @param   ascending
        *          <code>true</code> if sort should be ascending;
        *          <code>false</code> if it should be descending.
        */
       protected BasicSorter(boolean ascending)
       {
          this.direction = (ascending ? 1 : -1);
       }

       /**
        * Compare two <code>Comparable</code> instances to determine relative
        * sort order.  The comparison uses the natural order of the objects,
        * except that unknown value always sorts high in an ascending sort.  The
        * result is inverted for descending sorts (meaning unknown value sorts low
        * in a descending sort.
        *
        * @param   d1
        *          First value to compare.  Must not be <code>null</code>.
        * @param   d2
        *          Second value to compare.  Must not be <code>null</code>.
        *
        * @return  Positive value if <code>d1</code> &gt; <code>d2</code>;
        *          negative value if <code>d1</code> &lt; <code>d2</code>;
        *          <code>0</code> if <code>d1</code> and <code>d2</code> sort
        *          equivalently.
        */
       public int compare(T d1, T d2)
       {
          int result = d1.compareTo(d2);

          return (result * direction);
       }

       /**
        * Calculate a hash code for this object.
        *
        * @return  Hash code.
        */
       public int hashCode()
       {
          int result = 17;
          result = 37 * result + direction;

          return result;
       }

       /**
        * Test for equality between this comparator and another.  Equality means
        * either both comparators represent the same object instance in memory,
        * or that both comparators are instances of this class and sort in the
        * same direction.
        *
        * @return  <code>true</code> if objects are equal, else
        *          <code>false</code>.
        */
       public boolean equals(Object o)
       {
          if (this == o)
          {
             return true;
          }

          if (!(o instanceof BasicSorter))
          {
             return false;
          }

          BasicSorter<T> that = (BasicSorter<T>) o;

          return (this.direction == that.direction);
       }

       /**
        * Report the direction in which this sorter sorts its data.
        *
        * @return  1 if ascending or -1 if descending.
        */
       protected int getDirection()
       {
          return direction;
       }
    }