code

  @EventHandler

        public void onHoldShield(PlayerItemHeldEvent e){


	       Player hero = e.getPlayer();
	         ItemStack item = hero.getItemInHand();
	           Material item2 = item.getType();



	           if(item2 == Material.IRON_TRAPDOOR){

	        	     PotionEffect effect = PotionEffectType.REGENERATION.createEffect(999999999, 1);
	                 hero.addPotionEffect(effect,true);

	         }
	           else{
	        	   hero.removePotionEffect(PotionEffectType.REGENERATION);
	           }

	   }