code: private List<List<String>> decodeTables(String[] tablesThatMustBeEmpty) {
          List<List<String>> answer = new ArrayList<>();
          for (String tableSet : tablesThatMustBeEmpty) {
              String tableNames[] = tableSet.split("\\+");
              answer.add(Arrays.asList(tableNames));
          }
          return answer;
      }
docs: Decode sets of names encoded as by concatenation with plus signs
  into lists of lists of strings.  Preserve the order, since we need
  it to match to error messages later on.
  
  @param tablesThatMustBeEmpty
  @return The decoded lists.