/*
 * GRAL: GRAphing Library for Java(R)
 *
 * (C) Copyright 2009-2016 Erich Seifert ,
 * Michael Seifert 
 *
 * This file is part of GRAL.
 *
 * GRAL is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * GRAL 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with GRAL.  If not, see .
 */
package de.erichseifert.gral.data.comparators;

import de.erichseifert.gral.data.Record;

/**
 * Class that represents a {@code DataComparator} for comparing two records
 * at a defined index for descending order.
 * @see de.erichseifert.gral.data.DataTable#sort(DataComparator...)
 */
public class Descending extends DataComparator {
	/** Version id for serialization. */
	private static final long serialVersionUID = 6834583772451304014L;

	/**
	 * Creates a new Descending object sorting according to the specified
	 * column.
	 * @param col Column index to be compared
	 */
	public Descending(int col) {
		super(col);
	}

	/**
	 * 
Compares the values of two records at the specified column for order and
	 * returns a corresponding integer:

	 * 
    
	 *   
  • a negative value means {@code record1} is larger than {@code record2}
    • 
	 *   
  • 0 means {@code record1} is equal to {@code record2}
    • 
	 *   
  • a positive value means {@code record1} is smaller than {@code record2}
    • 
	 * 

	 * @param record1 First value
	 * @param record2 Second value
	 * @return An integer number describing the order:
	 *         a negative value if {@code record1} is larger than {@code record2},
	 *         0 if {@code record1} is equal to {@code record2},
	 *         a positive value if {@code record1} is smaller than {@code record2},
	 */
	@SuppressWarnings("unchecked")
	public int compare(Record record1, Record record2) {
		Comparable value1 = record1.get(getColumn());
		Comparable value2 = record2.get(getColumn());

		// null values sort as if larger than non-null values
		if (value1 == null && value2 == null) {
			return 0;
		} else if (value1 == null) {
			return -1;
		} else if (value2 == null) {
			return 1;
		}

		return value2.compareTo(value1);
	}
}

 
 


        
        

                    




        
      

      
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