Prevent Command if Inventory is not empty

How would I do this for the command /test? Does it use the PlayerCommandPreprocessEvent?

 

Dysko For a new command or one from another plugin?

 

Skionz

A new command that is also in the plugin.

 

I believe this tells you how to make a new command: http://wiki.bukkit.org/Plugin_Tutorial

 

Googlelover1234
I know how to make a command. I'm asking how to prevent the command if the player's inventory is not empty.

 

Dysko
I believe you could loop through the contents of the inventory, and if an item is != to air, then do whatever.

 

Googlelover1234

Code:java

private boolean isInventoryEmpty(Player player) {
        for (ItemStack item : player.getInventory().getContents()) {
            if (!item.equals(Material.AIR)) {
                return false;
            }
        }
        return true;
    }

I am using this code here but it's giving a null pointer exception on the if statement.

 

Code:

@EventHandler
    public void cancelEmptyInventory(PlayerCommandPreprocessEvent e)
    {
        Player p = e.getPlayer();
        if(!p.getInventory().getContents() == null && !p.getInventory().getArmorContents() == null)
        {
            e.setCancelled(true);
            p.sendMessage(ChatColor.RED + "Your command was cancelled!");
        }
    }