[Tutorial]Particle effects for arrows

Slikey I've made this when I was learning java/bukkit for like 3 months or something. obviously I can do better than this.

 

Slikey I've updated my code . no runnables running when theres no arrow getting shot
Thanks for the method. I'll give you credit at the original post

Code:

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;
 
import net.minecraft.server.v1_7_R4.Packet;
import net.minecraft.server.v1_7_R4.PacketPlayOutWorldParticles;
 
import org.bukkit.Bukkit;
import org.bukkit.Location;
import org.bukkit.craftbukkit.v1_7_R4.entity.CraftPlayer;
import org.bukkit.entity.Arrow;
import org.bukkit.entity.Entity;
import org.bukkit.entity.Player;
import org.bukkit.entity.Projectile;
import org.bukkit.event.EventHandler;
import org.bukkit.event.Listener;
import org.bukkit.event.entity.EntityShootBowEvent;
import org.bukkit.event.entity.ProjectileHitEvent;
import org.bukkit.plugin.java.JavaPlugin;
import org.bukkit.scheduler.BukkitRunnable;
 
/**
* @author Funergy
*
*/
public class ParticleArrows extends JavaPlugin implements Listener{
        public ArrayList<Projectile> arrows = new ArrayList<Projectile>();
   
        public void onEnable() {
        Bukkit.getPluginManager().registerEvents(this, this);//Removed the Bukkit Runnable
        }
   
        @EventHandler
        public void onShootBow(EntityShootBowEvent e){
            arrows.add((Projectile) e.getProjectile());
            addParticleEffect((Projectile)e.getProjectile());
           
   
   
        }
        @EventHandler
        public void onProjectileHit(ProjectileHitEvent e){
            if(e.getEntity() instanceof Arrow){
            arrows.remove(e.getEntity());
 
            }
        }
      //moved the Bukkit runnable to a single method and not in the onEnable
        @SuppressWarnings("deprecation")
        public void addParticleEffect(final Projectile entity){
            new BukkitRunnable(){
 
                @Override
                public void run() {
                    if(arrows.contains(entity)){//if the arrow still is in the air
                        Map<Player, Location> locationCache = new HashMap<>();
                        for (Player online : Bukkit.getOnlinePlayers()) {
                              locationCache.put(online, online.getLocation());
                           
                        }
                          Location loc = entity.getLocation();
                          Packet packet = new PacketPlayOutWorldParticles("flame",
                              (float) loc.getX(),  (float) loc.getY(), (float) loc.getZ(),
                              0, 0, 0,
                              0, 1);
                         
                          for (Map.Entry<Player, Location> entry : locationCache.entrySet()) {
                              if(entry.getKey().isOnline()){
                               
                                  //If the player has left when the arrow was going. we should remove him from the map to avoid NPE's
                            if (entry.getValue().getWorld() == loc.getWorld() &&
                                entry.getValue().distanceSquared(loc) <= 16*16) {
                              ((CraftPlayer) entry.getKey()).getHandle().playerConnection.sendPacket(packet);
 
                            }
               
                          }
                    }
                    }else{//we cancel the event when the arrow isn't in the air anymore.
                        this.cancel();
                        return;
                    }
        }
            }.runTaskTimer(this, 0, 1);
        }
   
 
}