docs: public int getNumLockedObjects() {
          int result = 0;
          for (int i = 0; i + 1 < array.length; i += 2) {
              if (array[i] == INVALID) {
                  break;
              }
              if (array[i + 1] > 0) {
                  ++result;
              }
          }
          return result;
      }