code: public void diagnostics() {
          log.finest("Thread count = " + threadCounter);
          if (threadCounter.get() > 0) {
              log.finest("Thread names:");
              synchronized (threadNames) {
                  for (String name : threadNames) {
                      log.finest("\t" + name);
                  }
              }
          }
      }
docs: This method reports diagnostic information to the log.