a module implementation for DiscordEmoji4J - https://github.com/nerd/DiscordEmoji4J

Demoji.java

import io.github.nerd.discordemoji.CustomEmoji;
import io.github.nerd.discordemoji.EmojiRegistry;
import sx.blah.discord.api.IDiscordClient;
import sx.blah.discord.api.events.IListener;
import sx.blah.discord.handle.impl.events.guild.GuildCreateEvent;
import sx.blah.discord.handle.impl.events.guild.GuildEmojisUpdateEvent;
import sx.blah.discord.handle.obj.IEmoji;
import sx.blah.discord.handle.obj.IGuild;
import sx.blah.discord.modules.IModule;

import java.util.HashMap;
import java.util.Map;

/**
 * @author ashley
 * @since 5/3/17 2:41 AM
 */
public class Demoji implements IModule {
	private final Map<Long, EmojiRegistry> registries = new HashMap<>();

	@Override
	public boolean enable(IDiscordClient client) {
		for (IGuild guild : client.getGuilds()) {
			this.registerEmojisFromGuild(guild);
		}

		client.getDispatcher().registerListener(new IListener<GuildCreateEvent>() {
			@Override
			public void handle(GuildCreateEvent event) {
				Demoji.this.registerEmojisFromGuild(event.getGuild());
			}
		});

		client.getDispatcher().registerListener(new IListener<GuildEmojisUpdateEvent>() {
			@Override
			public void handle(GuildEmojisUpdateEvent event) {
				if (registries.containsKey(event.getGuild().getLongID()))
					registries.remove(event.getGuild().getLongID());
				Demoji.this.registerEmojisFromGuild(event.getGuild());
			}
		});
		return true;
	}

	@Override
	public void disable() {
		registries.clear();
	}

	@Override
	public String getName() {
		return "Demoji";
	}

	@Override
	public String getAuthor() {
		return "Ashley Null";
	}

	@Override
	public String getVersion() {
		return "1.0";
	}

	@Override
	public String getMinimumDiscord4JVersion() {
		return "2.8.0";
	}

	private void registerEmojisFromGuild(IGuild guild) {
		EmojiRegistry registry;
		registries.put(guild.getLongID(), registry = new EmojiRegistry());
		for (IEmoji emoji : guild.getEmojis()) {
			registry.registerEmoji(this.createEmojiFromInternal(emoji));
		}
	}

	private CustomEmoji createEmojiFromInternal(IEmoji emoji) {
		return new CustomEmoji(emoji.getLongID(), emoji.getName(), emoji.getGuild().getLongID());
	}

	public EmojiRegistry getRegistryForGuild(IGuild guild) {
		if (!registries.containsKey(guild.getLongID()))
			registerEmojisFromGuild(guild);

		return registries.get(guild.getLongID());
	}
}

TestBot.java

import io.github.nerd.demoji.Demoji;
import io.github.nerd.discordemoji.CustomEmoji;
import io.github.nerd.discordemoji.Emoji;
import io.github.nerd.discordemoji.EmojiRegistry;
import sx.blah.discord.api.ClientBuilder;
import sx.blah.discord.api.IDiscordClient;
import sx.blah.discord.api.events.IListener;
import sx.blah.discord.handle.impl.events.guild.channel.message.MessageReceivedEvent;

import java.util.ArrayList;
import java.util.Comparator;
import java.util.List;

/**
 * @author ashley
 * @since 5/3/17 2:55 AM
 */
public class TestBot {
	public static void main(String... args) {
		IDiscordClient client = new ClientBuilder().withToken(args[0]).build();
		client.login();
		Demoji demoji = new Demoji();
		client.getModuleLoader().loadModule(demoji);

		client.getDispatcher().registerListener(new IListener<MessageReceivedEvent>() {
			@Override
			public void handle(MessageReceivedEvent e) {
				if (e.getMessage().getContent().startsWith("!emojis")) {
					StringBuilder builder = new StringBuilder();
					EmojiRegistry registry = demoji.getRegistryForGuild(e.getGuild());
					List<Emoji> emojis = new ArrayList<>(registry.getEmojis());
					emojis.sort(Comparator.comparing(o -> o.getAliases().get(0))); // optional - makes it pretty
					for (Emoji emoji : emojis)
						if (emoji instanceof CustomEmoji)
							builder.append(emoji.toString()).append('\n');
					e.getMessage().reply(builder.toString());
				}
			}
		});
	}
}