package org.example.javaset;import java.util.*;public class TestSet {    public static void main(String[]args){        Message[] messages={                new Message(1, "Hello!"),                new Message(2, "发工资了吗？"),                new Message(2, "发工资了吗？"),                new Message(3, "去哪吃饭？"),                new Message(3, "去哪吃饭？"),                new Message(4, "Bye")        };        List<Message>received=new ArrayList<>(Arrays.asList(messages));        List<Message> displayMessages = process(received);        for (Message message : displayMessages) {            System.out.println(message.text);        }    }    static List<Message> process(List<Message> received) {        Set<Message>messageSet=new TreeSet<>();        for(Message message:received){            messageSet.add(message);        }        received=new ArrayList<>();        for(Message message:messageSet){            received.add(message);        }        return received;    }}class Message implements Comparable{    public final int sequence;    public final String text;    public Message(int sequence, String text) {        this.sequence = sequence;        this.text = text;    }    @Override    public int compareTo(Object o) {        if(o instanceof Message){            Message m=(Message) o;            return Integer.compare(this.sequence,m.sequence);        }        return 0;    }}