code: public String toPerformanceString() {
          final StringBuilder res = 
                  new StringBuilder()
                      .append(
                              quote(metric.getMetricName()))
                              .append('=')
                              .append((metric.getMetricValue(prefix)).toPrettyPrintedString());
  
          if (unitOfMeasure != null) {
              switch (unitOfMeasure) {
              case milliseconds:
                  res.append("ms");
                  break;
              case microseconds:
                  res.append("us");
                  break;
              case seconds:
                  res.append('s');
                  break;
              case bytes:
                  res.append('B');
                  break;
              case kilobytes:
                  res.append("KB");
                  break;
              case megabytes:
                  res.append("MB");
                  break;
              case gigabytes:
                  res.append("GB");
                  break;
              case terabytes:
                  res.append("TB");
                  break;
              case percentage:
                  res.append('%');
                  break;
              case counter:
                  res.append('c');
                  break;
              default:
              }
          }
  
          if (unit != null) {
              res.append(unit);
          }
  
          res.append(';');
          if (warningRange != null) {
              res.append(warningRange);
          }
          res.append(';');
          if (criticalRange != null) {
              res.append(criticalRange);
          }
          res.append(';');
          if (metric.getMinValue() != null) {
              res.append(metric.getMinValue(prefix).toPrettyPrintedString());
          }
          res.append(';');
          if (metric.getMaxValue() != null) {
              res.append(metric.getMaxValue(prefix).toPrettyPrintedString());
          }
  
          while (res.charAt(res.length() - 1) == ';') {
              res.deleteCharAt(res.length() - 1);
          }
  
          return res.toString();
      }
docs: Produce a performance string according to Nagios specification based on
  the value of this performance data object.
  
  @return a string that can be returned to Nagios