Need help fixing.

package me.caleb.minecraftbackpack;

import org.bukkit.Bukkit;
import org.bukkit.command.Command;
import org.bukkit.command.CommandSender;
import org.bukkit.entity.Player;
import org.bukkit.event.Listener;
import org.bukkit.inventory.Inventory;
import org.bukkit.plugin.java.JavaPlugin;

public class MinecraftBackpack extends JavaPlugin implements Listener {

	public static Inventory smallInventory;

	public void onEnable(){
		smallInventory = Bukkit.createInventory(null, 9,
				"Small Backpack");
		getServer().getPluginManager().registerEvents(this, this);
	}

	public boolean onCommand(CommandSender sender, Command command,
			String label, String[] args) {
		if (label.equalsIgnoreCase("backpack")) {
			if (sender instanceof Player) {
				((Player) sender).openInventory(smallInventory);
			}
		}
		return false;
	}


}