docs: public void add(final String key, final String value) {
          if (key != null) {
              final Argument argument;
              if (key.startsWith("-D")) {
                  if (value == null) {
                      argument = createSystemProperty(key);
                  } else {
                      argument = createSystemProperty(key, value);
                  }
              } else {
                  if (value == null) {
                      argument = create(key);
                  } else {
                      argument = create(key, value);
                  }
              }
              add(argument);
          }
      }