protected double getNextFailureTimeSample() {
        double sample;
        if (failureTimePatternDiscrete_ != null)
        {
            sample = failureTimePatternDiscrete_.sample();
            return Math.abs(sample);
        }
        else if (failureTimePatternCont_ != null)
        {
            sample = failureTimePatternCont_.sample();
            return Math.abs(sample);
        }
        else if (failureTimePatternVariate_ != null)
        {
            sample = failureTimePatternVariate_.gen();
            return Math.abs(sample);
        }
        else
            return -1;
    }