private ArrayList<String> killer1 = new ArrayList<String>(); //make the lore Arraylist

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

@EventHandler
public void onEntityKill(EntityDeathEvent e) {
Entity killed = (Entity) e.getEntity();
Player killer = (Player) e.getEntity().getKiller();
ItemStack is = killer.getInventory().getItemInHand();
ItemMeta kill = is.getItemMeta();
if(is == null) return; {
if (e.getEntity() instanceof Player || e.getEntity() instanceof Entity) {
if (e.getEntity().getKiller() instanceof Player) {
if (e.getEntity().isDead()) {
killer1.add(ChatColor.GREEN + "Kills: " + ChatColor.RED + +1 );
kill.setLore(killer1);

killer.sendMessage("Lore set");

//TODO: Update the lore
}
}
}
}
}