Command Arguments/Strings error message is 'wrong'!

Code:java

if(args.length == 1) {
 
                  ItemStack hat = new ItemStack(Material.getMaterial(args[0].toUpperCase()));
                if(args[0].equalsIgnoreCase(hat.getType().toString())) {
                    p.getInventory().setHelmet(hat);
                    ItemStack gotHat = p.getInventory().getHelmet();
                    p.getWorld().playEffect(p.getLocation(), Effect.MOBSPAWNER_FLAMES, 6);
                    p.sendMessage(ChatColor.GREEN + "You've changed your hat to " + ChatColor.RED + gotHat.getType());
 
                } else {
                    p.sendMessage(ChatColor.RED + "'" +args[0] + "' isn't a Material!");
                }
              } 

So my question is , the error message or when I'm typing in "/hat sdfkj" it isn't a material and you can see I've written an error message when you typed in something else what isn't a command and yeah that doesn't works!
The error message isn't "sdfkj isn't a Material!" its (typical)
"An internal error occured while attempting to perform this command"

What did I wrong? And yes my english is bad but i hope its understandable

 

Skrarity You are trying to create an ItemStack before you check if the material exists. That's causing your error.

 

I'm confused HOW I can check if the material exists???