问题

Method #1:

public static List<Member> getMembers() {
    return Arrays.stream(WebClient.builder().build()
        .get()
        .uri(URL)
        .header("Authorization", "Bot " + Credentials.TOKEN)
        .retrieve()
        .bodyToMono(Member[].class)
        .block()).collect(Collectors.toList());
}

This method only retrieves the last user that joined the server.

Method #2:

Guild guild = event.getJDA().getGuildById(GUILD_ID);

event.getChannel().sendMessage("Users: " + guild.getMembers().size()).queue();

This method retrieves only 2 users. While debugging, it was found that it's retrieving the bot itself and you.

Method #3:

public void onGuildMessageReceived(GuildMessageReceivedEvent event) {
    String messageSent = event.getMessage().getContentRaw();

    if (messageSent.equalsIgnoreCase("members")) {
        Guild guild = event.getJDA().getGuildById(GUILD_ID);

        event.getChannel().sendMessage("Users: " +
            guild.getMembers().size()).queue();            

        event.getChannel().sendMessage("Thats all for now").queue();
    }
}

This method behaves the same as Method #2.

Method #4:

public void onGuildMessageReceived(GuildMessageReceivedEvent event) {
    String messageSent = event.getMessage().getContentRaw();

    event.getChannel().getMembers().forEach(member -> {
        event.getChannel().sendMessage("[Channel - " + event.getChannel().getName() + " ]").queue();

        event.getChannel().sendMessage("---- Members -> " + member.getUser().getName()).queue();
    });
}

This method behaves the same as Method #2 and #3.

It seems that in Methods #2, #3, and #4, you are encountering issues where it only retrieves the bot and yourself. This might be due to cached members. The documentation suggests that Guild.getMembers() will only check cached members.

To get all the users in a Guild or a channel, you might want to consider fetching members explicitly to ensure you get the complete list of members, even those not currently cached. You can use the retrieve() method to fetch members as follows:

Guild guild = event.getJDA().getGuildById(GUILD_ID);
guild.loadMembers().onSuccess(members -> {
    event.getChannel().sendMessage("Users: " + members.size()).queue();
});

This code will load all the members in the guild, and then you can access them without encountering the caching issue.

public static List<Member> getMembers() {
    return Arrays.stream(WebClient.builder().build()
        .get()
        .uri(URL)
        .header("Authorization", "Bot " + Credentials.TOKEN)
        .retrieve()
        .bodyToMono(Member[].class)
        .block()).collect(Collectors.toList());
}

Guild guild = event.getJDA().getGuildById(GUILD_ID);

event.getChannel().sendMessage("Users: " + guild.getMembers().size()).queue();

public void onGuildMessageReceived(GuildMessageReceivedEvent event) {
    String messageSent = event.getMessage().getContentRaw();
    
    if (messageSent.equalsIgnoreCase("members")) {
        Guild guild = event.getJDA().getGuildById(GUILD_ID);

        event.getChannel().sendMessage("Users: " +
            guild.getMembers().size()).queue();            
    
        event.getChannel().sendMessage("Thats all for now").queue();
    }
}

public void onGuildMessageReceived(GuildMessageReceivedEvent event) {
    String messageSent = event.getMessage().getContentRaw();
        
    event.getChannel().getMembers().forEach(member -> {
        event.getChannel().sendMessage("[Channel - " + event.getChannel().getName() + " ]").queue();
        
        event.getChannel().sendMessage("---- Members -> " + member.getUser().getName()).queue();
    });
}

答案1

得分: 1

event.getJDA().getGuildById(GUILD_ID).getMemberCount();

如 这个回答 中所述，你可以启用特权的服务器成员终端点并缓存所有成员。然而，如果未经验证，你的机器人最多只能加入 100 个服务器。

这个数量是精确的，但是缓存所有公会中的所有成员也会占用大量 RAM。

一个更好的解决方案是使用 公会终端点 中的成员数量。你可以向 /guilds/<id>?with_counts=true 发送 GET 请求，并使用 approximate_member_count。

甚至 JDA 也使用了这个终端点。
Guild 有一个方法 getMemberCount 可以获取该公会（近似的）成员数量。

<details>
<summary>英文:</summary>

# TL;DR

    event.getJDA().getGuildById(GUILD_ID).getMemberCount();

---

As described in [this answer](https://stackoverflow.com/a/61229594/10871900), you could enable the privileged server members endpoint and cache all members. Your bot can not join more than 100 servers without being verified then, however.

This amount is exact but caching all members in all guilds will also use up much RAM.

A way better solution is to use the count from [the guild endpoint](https://discord.com/developers/docs/resources/guild). You can send a GET request to `/guilds/&lt;id&gt;?with_counts=true` and use `approximate_member_count`.

JDA even uses this endpoint.
`Guild` has a method [`getMemberCount`](https://javadoc.io/static/net.dv8tion/JDA/4.2.0_203/net/dv8tion/jda/api/entities/Guild.html#getMemberCount()) that gives you the (approximate) number of members in this guild.

</details>