@Override
    void add(Number val) {
        double dval = val.doubleValue();
        last = dval;
        if (dval > max) {
            max = dval;
        }
        if (dval < min) {
            min = dval;
        }
        sum += dval;
        ++count;
    }
A metric which contains a gauge value, i.e a value which represents the magnitude of something
measured at a point in time. This metric value contains some additional information about the distribution
of this gauge value in the time interval this metric is for.

@author Simon Thoresen Hult
container-core/src/main/java/com/yahoo/container/jdisc/state/GaugeMetric.java