craterdog.utils.NaturalComparator Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of java-general-utilities Show documentation

A set of general Java utility classes.

There is a newer version: 3.12

Show newest version

/************************************************************************
 * Copyright (c) Crater Dog Technologies(TM).  All Rights Reserved.     *
 ************************************************************************
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.        *
 *                                                                      *
 * This code is free software; you can redistribute it and/or modify it *
 * under the terms of The MIT License (MIT), as published by the Open   *
 * Source Initiative. (See http://opensource.org/licenses/MIT)          *
 ************************************************************************/
package craterdog.utils;

import java.util.Comparator;


/**
 * This class defines a comparator that compares two objects of the same type using their natural
 * compareTo method if the type implements the Comparable interface, or
 * by doing a lexical comparison on their string formats if not.  This comparator handles
 * null values as well.  A null value is always less than an non
 * null value and two null values are equal.
 *
 * @author Derk Norton
 * @param  The type of the objects being compared.
 */
public class NaturalComparator implements Comparator {

    @Override
    public int compare(T object1, T object2) {
        if (object1 != null) {
            if (object2 == null) return 1;  // the second object is null
            if (object1 instanceof Comparable) {
                // use the natural ordering
                @SuppressWarnings("unchecked")
                Comparable comparable1 = (Comparable) object1;
                return comparable1.compareTo(object2);
            } else if (object1.getClass().isArray()) {
                // compare the elements in the arrays
                Object[] array1 = (Object[]) object1;
                Object[] array2 = (Object[]) object2;
                return compareArrays(array1, array2);
            } else {
                // use lexical ordering
                String string1 = object1.toString();
                String string2 = object2.toString();
                return string1.compareTo(string2);
            }
        }
        if (object2 != null) {
            return -1;  // first object is null
        }
        return 0;  // both objects are null
    }


    static private int compareArrays(Object[] array1, Object[] array2) {
        Comparator