code: public void set( ValueMetric metric,
                       long value ) {
          assert metric != null;
          ValueHistory history = values.get(metric);
          if (history != null) history.recordNewValue(value);
      }
docs: Record a specific value for a metric, called by the code that knows when and how the metric changes.
  
  @param metric the metric; may not be null
  @param value the value for the metric
  @see #increment(ValueMetric, long)
  @see #decrement(ValueMetric)
  @see #recordDuration(DurationMetric, long, TimeUnit, Map)