code: protected void updateCoreLength() {
  		if (getBlockSets().size() == 0) {
  			throw new IndexOutOfBoundsException(
  					"Empty MultipleAlignment: blockSets size == 0.");
  		} // Otherwise try to calculate it from the BlockSet information
  		else {
  			coreLength = 0;
  			for (BlockSet blockSet : blockSets)
  				coreLength += blockSet.getCoreLength();
  		}
  	}
docs: Force recalculation of the core length (ungapped columns) based on the
  BlockSet core lengths.