JoinFirework.java

package me.pogostick29.joinfirework;

import org.bukkit.Bukkit;
import org.bukkit.Color;
import org.bukkit.FireworkEffect;
import org.bukkit.FireworkEffect.Type;
import org.bukkit.entity.Firework;
import org.bukkit.event.EventHandler;
import org.bukkit.event.Listener;
import org.bukkit.event.player.PlayerJoinEvent;
import org.bukkit.inventory.meta.FireworkMeta;
import org.bukkit.plugin.java.JavaPlugin;

public class JoinFirework extends JavaPlugin implements Listener {

    public void onEnable() {
        Bukkit.getServer().getPluginManager().registerEvents(this, this);
    }

    @EventHandler
    public void onPlayerJoin(final PlayerJoinEvent e) {
        Bukkit.getServer().getScheduler().scheduleSyncDelayedTask(this, new Runnable() {
            public void run() {
                Firework f = (Firework) e.getPlayer().getWorld().spawn(e.getPlayer().getLocation(), Firework.class);

                FireworkMeta fm = f.getFireworkMeta();
                fm.addEffect(FireworkEffect.builder()
                        .flicker(false)
                        .trail(true)
                        .with(Type.CREEPER)
                        .withColor(Color.GREEN)
                        .withFade(Color.BLUE)
                        .build());
                fm.setPower(3);
                f.setFireworkMeta(fm);
            }
        }, 20);
    }
}