docs: synchronized TriggerData popPair() {
  
          if (rowsQueued == 0) {
              try {
                  wait();    // this releases the lock monitor
              } catch (InterruptedException e) {
  
                  /* ignore and resume */
              }
          }
  
          rowsQueued--;
  
          notify();    // notify push's wait
  
          if (pendingQueue.size() == 0) {
              return null;
          } else {
              return (TriggerData) pendingQueue.removeFirst();
          }
      }