Chest Problem

package me.MrGriefer_.SurvivalGames;

import java.util.Random;

import org.bukkit.Material;
import org.bukkit.block.Chest;
import org.bukkit.entity.Player;
import org.bukkit.inventory.ItemStack;

public class ChestManager {

	private Chest chest;
	private int tier;

	private Player p;

	public ChestManager(Chest chest, int tier) {
		this.chest = chest;
		this.tier = tier;
	}

	public Chest getChest() {
		return chest;
	}

	public int getTier() {
		return tier;
	}

	public void fillChest() {
		Arena a = ArenaManager.getInstance().getArena(p);

		if (a.getBounds().contains(p.getLocation())) {
			Material[] items1 = new Material[] { Material.WOOD_AXE, Material.LEATHER_BOOTS, Material.GOLD_HELMET, 	    Material.STRING, Material.APPLE, Material.ARROW };
			Material[] items2 = new Material[] { Material.COOKED_BEEF, Material.RAW_CHICKEN, Material.RAW_FISH, Material.MUSHROOM_SOUP, Material.WOOD_SWORD, Material.GOLD_LEGGINGS, Material.MELON };

			Random r = new Random();

			int numItems = r.nextInt(5) + 1;

			for (int i = 0; i < numItems; i++) {
				Material material = null;

				if (tier == 1) {
					material = items1[r.nextInt(items1.length)];
				}

				else if (tier == 2) {
					material = items2[r.nextInt(items2.length)];
				}

				ItemStack item = new ItemStack(material, 1);

				int index;

				do {
						index = r.nextInt(chest.getInventory().getSize());
				} while (chest.getInventory().getItem(index) != null);

				chest.getInventory().setItem(index, item);
			}
		}
	}
}