gistfile1.txt

    final Parser<User> = new Parser<>() {
        private final Pattern DISCRIM_PATTERN = Pattern.compile("(.+)#(\\d+)");
        private final Pattern MENTION_OR_ID_PATTERN = Pattern.compile("(<@)?(\\d+)(>)?");

        public User parse(String input, ParseContext context) {
                Matcher discrimMatcher = DISCRIM_PATTERN.matcher(input);
                Matcher mentionMatcher = MENTION_OR_ID_PATTERN.matcher(input);

                if (discrimMatcher.matches()) {
                    // use the groups for discrim
                } else if (mentionMatcher.matches()) {
                        // use the groups for id
                }
                return null;
        }
    }

        new SimpleType<User>(User.class, "user", "users?") {

            @Override
            public User parse(String s, ParseContext pc) {
                return USER_PARSER.parse(s, pc);
            }

            @Override
            public boolean canParse(ParseContext pc) {
                return pc == ParseContext.COMMAND;
            }

            @Override
            public String toString(User user, int arg1) {
                return user.getName();
            }

            @Override
            public String toVariableNameString(User user) {
                return user.getId();
            }

        };

        new SimpleType<Member>(Member.class, "member", "members?") {

            @Override
            public Member parse(String s, ParseContext pc) {
        User user = USER_PARSER.parse(s, pc);
        // convert to member
                return member;
            }

            @Override
            public boolean canParse(ParseContext pc) {
                return pc == ParseContext.COMMAND;
            }

            @Override
            public String toString(Member member, int arg1) {
                return member.getUser().getName();
            }

            @Override
            public String toVariableNameString(Member member) {
                return member.getUser().getId();
            }

        };