How do I decompile Minecraft?

I'm trying to get started modding Minecraft. I opened up the minecraft.jar file in Eclipse, but it doesn't contain what I expected.

In this tutorial the presenter decompiles minecraft.jar and finds things like armor and blocks packages, but when I put my minecraft.jar file (from [user]\appdata\roaming\.minecraft) into Eclipse, I only see Apache and Ydggrassil authentication and such.

What am I doing wrong?

• This question should be closed as an attempt at a breach of copywrite. – War Aug 10 '14 at 18:00
• This topic is perfectly acceptable here, but I am not really sure this is a good question for this site. – user1430 Aug 10 '14 at 18:08
• fair enough, someone pointed out that EULA allows this (wierd but cool) :) – War Aug 10 '14 at 18:10
• Why is this not a good question for this site? – vroomvsr Aug 10 '14 at 18:29
• @Wardy Just to seal it with a reference: Here's the EULA. It says "If you've bought the Game, you may play around with it and modify it." – Anko Aug 12 '14 at 15:18

You can't just open the jar in Eclipse. Even if you have some kind of decompiler-plugin, you will only see obfuscated code.

You will need the Minecraft Coder Pack to decompile and deobfuscate the jar (as well as MCP can anyway) so you can work with the code.

Additionally, if you want do develop Minecraft-Forge mods you should check out this page. Forge also requires MCP to decompile the jar, but it's automatically downloaded during installation.