Cannot create single member cluster about jgroups-raft HOT 7 CLOSED

package org.jgroups.protocols.raft;

import org.jgroups.Event;
import org.jgroups.Header;
import org.jgroups.Message;
import org.jgroups.stack.Protocol;
import org.jgroups.util.ExtendedUUID;

public class SINGLE_MEMBER extends Protocol {
    
    private RAFT raft;
    private ELECTION election;

    @Override
    public void init() throws Exception {
        raft=findProtocol(RAFT.class);
        election=findProtocol(ELECTION.class);
        super.init();
    }

    private  <T extends Protocol> T findProtocol(Class<T> clazz) {
        for(Protocol p=up_prot; p != null; p=p.getUpProtocol()) {
            if(p.getClass().equals(clazz))
                return (T)p;
        }
        throw new IllegalStateException(clazz.getSimpleName() + " not found above " + this.getClass().getSimpleName());
    }

    @Override
    public Object down(Message msg) {
        if (this.isSingleMember()) {
            Header electionHeader = msg.getHeader(election.getId());
            Header raftHeader = msg.getHeader(raft.getId());
            if (raftHeader != null && electionHeader != null) {
                throw new IllegalStateException("Message contains a raft[" + raftHeader.getClass() + "] and election[" + electionHeader.getClass() + "] headers.");
            }
            if (raftHeader != null) {
                handleRaftHeader(raftHeader);
            } else if (electionHeader != null) {
                handleElectionHeader(electionHeader);
            }
            return null;
        }
        return super.down(msg);
    }

    private void handleElectionHeader(Header header) {
        if (header instanceof VoteRequest) {
            VoteRequest voteRequest = (VoteRequest)header;
            VoteResponse voteResponse = new VoteResponse(voteRequest.term(), true);
            Message message = new Message();
            message.putHeader(election.getId(), voteResponse);
            this.up(message);
        }
    }

    private void handleRaftHeader(Header header) {
        if (header instanceof AppendEntriesRequest) {
            AppendEntriesRequest req = (AppendEntriesRequest) header;
            AppendResult appendResult = new AppendResult(true, req.prev_log_index + 1).commitIndex(raft.commitIndex());
            AppendEntriesResponse resp = new AppendEntriesResponse(req.term(), appendResult);

            /* Generate random sender because the leader has already voted */
            ExtendedUUID randomSender = ExtendedUUID.randomUUID();
            Message message = new Message(raft.leader()).src(randomSender);
            message.putHeader(raft.getId(), resp);
            this.up(message);
        }
    }

    private boolean isSingleMember() {
        return raft.majority() == 1;
    }
}