code: protected Double addDoubleValue(Object name, double inc) {
      Double val = this.doubleCounters.get(name);
      Double retv = null;
      if (val == null) {
        retv = new Double(inc);
      } else {
        retv = new Double(val.doubleValue() + inc);
      }
      this.doubleCounters.put(name, retv);
      return retv;
    }
docs: Increment the given counter by the given incremental value If the counter
  does not exist, one is created with value 0.
  
  @param name
  the counter name
  @param inc
  the incremental value
  @return the updated value.