Solved Canceling a Runnable

Code:java

 ItemStack apowerup = new ItemStack(Material.ARROW, 3);
final Item a = loc.getWorld().dropItem(loc, apowerup);
task1 = Bukkit.getScheduler().scheduleSyncRepeatingTask((Plugin) HGTraining.getPluginInstance(), new Runnable(){
 
@Override
public void run() {
if(a.isDead()){
Bukkit.getScheduler().cancelTask(task1);
}
ParticleEffect.INSTANT_SPELL.display(a.getLocation(), 0.4F, 0.4F, 0.4F, 1, 20);
 
a.getWorld().playSound(a.getLocation(), Sound.FIREWORK_BLAST, 2.0F, 2.0F);
}
}, 0, 10);

It works great however, it don't cancel if more than one item is picked up together :/ What's the best way to do this?

I have tried:

Code:java

if(a.isOnGround()){
if(a == null){
if(a.isValid){
if(a.isEmpty){
 
 

Also when a person picks the power up it removed it.

Code:java

@EventHandler
    public void itempickup(PlayerPickupItemEvent e){
        Player p = e.getPlayer();
 
        if(e.getItem().getItemStack().getType() == Material.ARROW){
            Item a = e.getItem();
            e.getItem().remove();
            e.setCancelled(true);
     }
}