code: @Override
      public double fast()
      {
          readLock.lock();
          try
          {
              int count = count();
              return toDegrees(sinSum / count, cosSum / count);
          }
          finally
          {
              readLock.unlock();
          }
      }
docs: Returns fast average. Fast calculation adds and subtracts values from
  sum field. This might cause difference in time to actual calculating
  sample by sample.
  @return