报错信息：class com.company.Message cannot be cast to class java.lang.Comparable (com.company.Message is in unnamed module of loader 'app'; java.lang.Comparable is in module java.base of loader 'bootstrap')

Set<Message> set = new TreeSet<Message>(received);//        set.addAll(received);

class Message implements Comparable<Message>

 @Override  public int compareTo(Message o) {        return this.sequence - o.sequence;    }

用Comparator正常运行

 Set<Message> set = new TreeSet<>(new Comparator<Message>() {//            @Override//            public int compare(Message o1, Message o2) {//                return o1.sequence - o2.sequence;//            }//        });

目前未搜索到原因。