Alphanumeric String Sorting using Java

Alphanumeric is a combination of alphabetic and numeric characters (sometimes shortened to alphameric).

In computing, the alphanumeric Strings can be seen very common to represent various codes etc. Sorting the alphanumeric strings can sometimes be a trouble by using regular sort techniques.

import java.util.Arrays;
import java.util.Comparator;
 
public class AlphanumericSorting implements Comparator {
    /**
     * The compare method that compares the alphanumeric strings
     */
    public int compare(Object firstObjToCompare, Object secondObjToCompare) {
        String firstString = firstObjToCompare.toString();
        String secondString = secondObjToCompare.toString();
 
        if (secondString == null || firstString == null) {
            return 0;
        }
 
        int lengthFirstStr = firstString.length();
        int lengthSecondStr = secondString.length();
 
        int index1 = 0;
        int index2 = 0;
 
        while (index1 < lengthFirstStr && index2 < lengthSecondStr) {
            char ch1 = firstString.charAt(index1);
            char ch2 = secondString.charAt(index2);
 
            char[] space1 = new char[lengthFirstStr];
            char[] space2 = new char[lengthSecondStr];
 
            int loc1 = 0;
            int loc2 = 0;
 
            do {
                space1[loc1++] = ch1;
                index1++;
 
                if (index1 < lengthFirstStr) {
                    ch1 = firstString.charAt(index1);
                } else {
                    break;
                }
            } while (Character.isDigit(ch1) == Character.isDigit(space1[0]));
 
            do {
                space2[loc2++] = ch2;
                index2++;
 
                if (index2 < lengthSecondStr) {
                    ch2 = secondString.charAt(index2);
                } else {
                    break;
                }
            } while (Character.isDigit(ch2) == Character.isDigit(space2[0]));
 
            String str1 = new String(space1);
            String str2 = new String(space2);
 
            int result;
 
            if (Character.isDigit(space1[0]) && Character.isDigit(space2[0])) {
                Integer firstNumberToCompare = new Integer(Integer
                        .parseInt(str1.trim()));
                Integer secondNumberToCompare = new Integer(Integer
                        .parseInt(str2.trim()));
                result = firstNumberToCompare.compareTo(secondNumberToCompare);
            } else {
                result = str1.compareTo(str2);
            }
 
            if (result != 0) {
                return result;
            }
        }
        return lengthFirstStr - lengthSecondStr;
    }
 
    /**
     * Testing the alphanumeric sorting
     */
    public static void main(String[] args) {
        String[] alphaNumericStringArray = new String[] { "NUM10071",
                "NUM9999", "9997", "9998", "9996", "9996F" };
 
        /*
         * Arrays.sort method can take an unsorted array and a comparator
         * to give a final sorted array.
         *
         * The sorting is done according to the comparator that we have
         * provided.
         */
        Arrays.sort(alphaNumericStringArray, new AlphanumericSorting());
 
        for (int i = 0; i < alphaNumericStringArray.length; i++) {
            System.out.println(alphaNumericStringArray[i]);
        }
 
    }
 
}