Minecraft - How do I check if someone has a clear inventory

Question

How do I check if a player has a clear inventory? I'm making a PvP arena plugin but I need it so when someone types /pvp join, it checks if they have a clear inventory. If they do have a clear inventory, it lets them join, if they don't, it asks them to.

I tried this but it's not reliable as there are more slots:

if(p.getInventory().getArmorContents() == null
    && p.getInventory().getItemInHand() == null
    && p.getInventory().getItemInHand() == null) {

Then I tried this but it did not work:

if (p.getInventory().getContents().length == 0) {

Answer 1

You could try to accomplish it by looping through player's inventor and checking if Nth slot in his inventory is empty, if it isn't -- the function returns false.

    private boolean hasItems(ItemStack item) {
        for (int i=0; i<=thePlayer.inventory.getSizeInventory()-5; i++) {
             if (thePlayer.inventory.mainInventory[i].itemId != NULL) {
                 return false;
             }
        }
        return true;
    }

You subtract 1 from the getSizeInventory() because it returns length and the arrays in Java are zero-based, and 4 because crafting slots count as well (I guess).