code: public void setOptDLower(boolean optDLower) {
      checkCanSetDeleteOption("-d");
      if (optDLower && optDUpper) {
        throw new IllegalArgumentException(ExceptionMessageMap.getMessage("000120")
            + "  -d cannot be used with -D.");
      } 
      this.optDLower = optDLower;
    }
docs: Checks whether the -d option should be set and sets it.
  
  @param optDLower True if the -d option should be used, false otherwise.