How to open a gui when a command is ran

So I'm trying to create a gui for staff members that will have the option to vanish or clear the chat etc. This is the code I have so far

Code:

package me.Server.devtest.command;

import org.bukkit.ChatColor;
import org.bukkit.command.Command;
import org.bukkit.command.CommandExecutor;
import org.bukkit.command.CommandSender;
import org.bukkit.entity.Player;

public class StaffCommand implements CommandExecutor {

    @Override
    public boolean onCommand(CommandSender sender, Command cmd, String lable, String[] args) {
        Player player = (Player) sender;
        if(sender instanceof Player){
            player.sendMessage(ChatColor.translateAlternateColorCodes('&', "&eOpening the staff GUI"));
        }
        else {
            sender.sendMessage("HEY! Only players can run this");
        }
        return true;
    }

}

Thanks in advance to anyone that helps me

 

Please search for an own solution first. Look in the bukkit api or search for threads.
But Anyways here's a small summary:

Code:

// Create your inventory : null is the inventoryholder, CHEST is the inventory type and the last parameter is the inventory name
Inventory inventory = Bukkit.getServer().createInventory(null, InventoryType.CHEST, "YourGUIName");

// Create an item
ItemStack beacon = new ItemStack(Material.BEACON);

// Add the item to the given inventory slot
inventory.setItem(0, beacon);

// Then you can open the inventory like this
p.openInventory(inventory);

Then use the InventoryClickEvent to do something when the player click's an item.