Version comparator for Denis

package org.sv.sandbox;

import java.util.Arrays;
import java.util.Comparator;

public class VersionComparator implements Comparator<String> {

	char[] alpha = new char[] {'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r'
			, 's', 't', 'u', 'v', 'w', 'x', 'y', 'z'};

	@Override
	public int compare(String versionA, String versionB) {
        if(versionA == null)
            return 1;
        if(versionB == null)
            return -1;

        String[] thisParts = versionA.split("\\.");
        String[] thatParts = versionB.split("\\.");
        int length = Math.max(thisParts.length, thatParts.length);
        for(int i = 0; i < length; i++) {
            int thisPart = i < thisParts.length ?
                prepareVersion(thisParts[i]) : 0;
            int thatPart = i < thatParts.length ?
        		prepareVersion(thatParts[i]) : 0;
            if(thisPart < thatPart)
                return -1;
            if(thisPart > thatPart)
                return 1;
        }
        return 0;
	}
	
	private int prepareVersion(String version) {
		if (!version.contains("-")) {
			return Integer.parseInt(version);
		}
		String[] parts = version.split("-");
		int weight = alpha.length - Arrays.binarySearch(alpha, parts[1].charAt(0));
		return Integer.parseInt(parts[0]) - (weight + 1);
	}

}