For some reason, my mod cannot use ItemStack.EMPTY. I look at the source codes for many other mods, and they use it just fine. I have to instead use ItemStack.field_190927_a. At least, I think that works, I'm not sure since there's other things in my code that also are not working even though they should be(for example, I can't override onBlockActivated for some strange reason). I'm using Idea, and I followed cpw's video on installing Forge through Idea. I wish I could give you a bit more details, but I've got no clue what the issue is. I'm using the latest version of forge, and I've tried reinstalling gradle and all that many times.

In your build.gradle file, you should change the mappings version to the latest. MCP mappings snapshots are published daily with the form of snapshot_YYYYMMDD, so today's would be snapshot_20161202.

Thanks! Sorry if this was an obvious thing, this is my first time ever touching modding.