logger.debug("Interrupted.", e);
                }
            }
        }

        public void awaitTermination(final long mills) {
            try {
                join(mills);
            } catch (final InterruptedException e) {
                if (logger.isDebugEnabled()) {
                    logger.debug("Interrupted.", e);
                }
            }

    // There are several well-known algorithms for rotating part of an array (or, equivalently,
    // exchanging two blocks of memory). This classic text by Gries and Mills mentions several:
    // https://ecommons.cornell.edu/bitstream/handle/1813/6292/81-452.pdf.
    // (1) "Reversal", the one we have here.

        queue[index] = elementData(minChildIndex);
        queue[minChildIndex] = x;
        return minChildIndex;
      }
      return crossOverUp(index, x);
    }

    /**
     * Fills the hole at {@code index} by moving in the least of its grandchildren to this position,
     * then recursively filling the new hole created.
     *