Example Container

package iitest.gui;

import iitest.capability.ITest;
import net.minecraft.entity.player.EntityPlayer;
import net.minecraft.inventory.Container;
import net.minecraft.inventory.IInventory;
import net.minecraft.inventory.Slot;
import net.minecraft.item.ItemStack;

public class TestContainer extends Container {

    public TestContainer(ITest cap, EntityPlayer player) {
        addSlotToContainer(new Slot(cap, 0, 0, 0));

        for (int y = 0; y < 4; y++) {
            for (int x = 0; x < 9; x++) {
                addSlotToContainer(new Slot(player.inventory, y * 9 + x, x * 18, y * 18 + 24));
            }
        }
    }

    @Override
    public boolean canInteractWith(EntityPlayer playerIn) {
        return true;
    }
}