Example Item

package iitest.item;

import iitest.IITest;
import iitest.capability.ITest;
import iitest.capability.ITestProvider;
import net.minecraft.creativetab.CreativeTabs;
import net.minecraft.entity.player.EntityPlayer;
import net.minecraft.item.Item;
import net.minecraft.item.ItemStack;
import net.minecraft.nbt.NBTTagCompound;
import net.minecraft.util.ActionResult;
import net.minecraft.util.EnumActionResult;
import net.minecraft.util.EnumHand;
import net.minecraft.world.World;
import net.minecraftforge.common.capabilities.ICapabilityProvider;

import javax.annotation.Nullable;

public class ItemTest extends Item {
    public ItemTest() {
        setCreativeTab(CreativeTabs.MISC);
    }

    public ActionResult<ItemStack> onItemRightClick(World worldIn, EntityPlayer playerIn, EnumHand handIn) {
        if (playerIn.isSneaking()) {
            playerIn.openGui(IITest.instance, 0, worldIn, 0, 0, 0);
        } else {
            ITest cap = playerIn.getHeldItem(handIn).getCapability(ITest.instance, null);
            cap.setValue(cap.getValue() + 1);
        }
        return new ActionResult(EnumActionResult.SUCCESS, playerIn.getHeldItem(handIn));
    }

    public ICapabilityProvider initCapabilities(ItemStack stack, @Nullable NBTTagCompound nbt) {
        return new ITestProvider();
    }
}