code: private void stopWorkers() {
          Record sentinel = Record.SENTINEL;
          for (int inx = 0; inx < m_workerList.size(); inx++) {
              try {
                  m_workerQueue.put(sentinel);
              } catch (InterruptedException e) {
                  // ignore
              }
          }
          
          for (LoadWorker loadWorker : m_workerList) {
              try {
                  loadWorker.join();
              } catch (InterruptedException e) {
                  // ignore
              }
          }
      }
docs: Add a sentinel to the queue for each worker and wait all to finish.