code: public Map<String, Object> rebuildIndex(String destinationIndex) {
  		MultivaluedMap<String, String> params = new MultivaluedHashMap<>();
  		params.putSingle("destinationIndex", destinationIndex);
  		return getEntity(invokeSignedRequest(getApiClient(), accessKey, key(true), POST,
  				getEndpoint(), getFullPath("_reindex"), null, params, new byte[0]), Map.class);
  	}
docs: Rebuilds the entire search index.
  @param destinationIndex an existing index as destination
  @return a response object with properties "tookMillis" and "reindexed"