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    • jidefx.utils.comparator.NaturalOrderComparator Maven / Gradle / Ivy

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    /*
 * @(#)DefaultComparator.java 5/19/2013
 *
 * Copyright 2002 - 2013 JIDE Software Inc. All rights reserved.
 */

package jidefx.utils.comparator;

import java.text.Collator;
import java.util.Comparator;

/**
 * This class compares objects as Comparable first, then convert them to Strings using the toString
 * methods. This is the default comparator used by the {@link ObjectComparatorManager} and should be able to handle most
 * comparison cases.
 */
public class NaturalOrderComparator implements Comparator {
    private static NaturalOrderComparator singleton = null;

    /**
     * Constructor.
     * 
    
     * Has protected access to prevent other clients creating instances of the class ... it is stateless so we need only
     * one instance.
     */
    protected NaturalOrderComparator() {
    }

    /**
     * Returns ObjectComparator singleton.
     *
     * @return an instance of DefaultComparator.
     */
    public static NaturalOrderComparator getInstance() {
        if (singleton == null)
            singleton = new NaturalOrderComparator();
        return singleton;
    }

    /**
     * Compares two Objects using the Comparable interface first. If not, it will use toString() methods to
     * compare them as two strings.
     *
     * @param o1 the first object to be compared
     * @param o2 the second object to be compared
     * @return 0 if a and b are equal, less than 0 if a $lt; b, grater than 0 if a > b.
     */
    public int compare(Object o1, Object o2) {
        if (o1 == null && o2 == null) {
            return 0;
        }
        else if (o1 == null) {
            return -1;
        }
        else if (o2 == null) {
            return 1;
        }

        if (o1 instanceof Comparable) {
            return ((Comparable) o1).compareTo(o2);
        }
        else if (o2 instanceof Comparable) {
            return 0 - ((Comparable) o2).compareTo(o1);
        }

        return Collator.getInstance().compare(o1.toString(), o2.toString());
    }
}
    
    
    
    

    




    
    
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