Version Strings Comparator for Java

VersionStringComparator.java

import java.util.Comparator;

/**
 * Both arguments need to be version Strings, formatted like "7.5.3", "2.3" "8.0.0.42"...
 *
 * If a version has more number length, it could be considered newer. Examples:
 *     "2.5" vs "2.5.1" -> a is older -> Negative int returned
 *     "2.6" vs "2.5.1" -> a is newer -> Positive int returned
 *     "2.5" vs "2.5.0" -> equal      -> Zero returned
 *
 * @return a positive int if A is newer than B, a negative int if A is older than B or zero if they are equal.
 */
public class VersionStringComparator implements Comparator<String> {

	private final static int NEWER =  1;
	private final static int EQUAL =  0;
	private final static int OLDER = -1;

	private final static String versionStringRegex = "^\\d+(?:\\.\\d+)*$";
	private final static String versionStringNumberSeparator = "\\.";

	@Override
	public int compare(String a, String b) {
		Integer nullChecks = nullChecks(a, b);
		if (nullChecks != null) return nullChecks; // One or both arguments are null

		assert a.matches(versionStringRegex);
		assert b.matches(versionStringRegex);

		String[] splittedA = a.split(versionStringNumberSeparator);
		String[] splittedB = b.split(versionStringNumberSeparator);
		int maxLen = Math.max(splittedA.length, splittedB.length);

		for(int i=0; i<maxLen; i++){
			int intA = getIntValueFromSplittedVersion(splittedA, i);
			int intB = getIntValueFromSplittedVersion(splittedB, i);
			if(intA != intB){
				return intA - intB;
			}
		}

		return EQUAL;
	}

	private Integer nullChecks(String a, String b){
		if      (a == null && b == null) return EQUAL;
		else if (a == null)              return OLDER;
		else if (b == null)              return NEWER;
		else return null;
	}

	private int getIntValueFromSplittedVersion(String[] splitted, int index){
		if(index < splitted.length)
			return Integer.parseInt(splitted[index]);
		else return 0; // return 0 for cases like "2.3.0" vs "2.3"
	}

}