private static final double RESULT_OF_DIVISION_BY_0 = 9.99;

public static double getPercentageDifference(long currentResult, long previousResult) {
    if (previousResult == 0 && currentResult == 0) {
        return 0;
    } else if (previousResult == 0) {
        return RESULT_OF_DIVISION_BY_0;
    } else {
        return (currentResult - previousResult) * 1.0 / previousResult;
    }
}