How would i set the player helmet as glowstone?

Ok, so i have this code, how do i set the players helmet as glowstone? I have it where it will place whats on his head into his inventory. But it wont set his helmet as glowstone.

Code:

package me.l4pierce.plugins.headlamp;
 
import org.bukkit.ChatColor;
import org.bukkit.Material;
import org.bukkit.command.Command;
import org.bukkit.command.CommandSender;
import org.bukkit.entity.Player;
import org.bukkit.event.Listener;
import org.bukkit.inventory.ItemStack;
import org.bukkit.inventory.PlayerInventory;
import org.bukkit.plugin.PluginDescriptionFile;
import org.bukkit.plugin.java.JavaPlugin;
 
public class Headlamp extends JavaPlugin implements Listener {
    private ItemStack GLOWSTONE;
    private ItemStack[] itemHelmet;
 
 
    @Override
    public void onEnable() {
        PluginDescriptionFile plugin = getDescription();
        System.out.println(plugin.getName() + " version " + plugin.getVersion() + " by l4pierce enabled.");
    }
 
    @Override
    public void onDisable() {
        PluginDescriptionFile plugin = getDescription();
        System.out.println(plugin.getName() + " version " + plugin.getVersion() + " by l4pierce disabled.");
    }
 
    @Override
    public boolean onCommand(CommandSender sender, Command cmd, String commandLabel, String[] args) {
        if (!(sender instanceof Player)) {
            sender.sendMessage(ChatColor.RED + "Sorry, but you dont seem to have a head for me to put some glowstone on :/");
            return false;
        }
        Player player = (Player) sender;
        if (commandLabel.equalsIgnoreCase("lamp")) {
            if (player.hasPermission("headlamp.use")|| player.hasPermission("headlamp.*") || player.isOp()) {{
                    PlayerInventory inventory = player.getInventory();
                    ItemStack itemHead = inventory.getHelmet();
                    inventory.addItem(itemHead);
                    inventory.setHelmet(GLOWSTONE);
                    player.sendMessage(ChatColor.GOLD + "Your path shall now be lit!");
                    player.sendMessage(ChatColor.DARK_RED + "Your previous helmet has been placed into your inventory!")
;                    return true;
 
                }
            } else {
                player.sendMessage(ChatColor.RED + "Your server admin has deemed you unfit to have a HeadLamp!");
                return true;
            }
        }
        return false;
    }
}

Thanks!

 

Shouldn't it be helmet...

Code:java

 
inventory.setHelmet(MATERIAL.GLOWSTONE)
 

??

 

Also, if you were trying to do this, which I did, putting a glowstone as your helmet does not light up the area.

 

I figured that out AFTER i coded it all xD