[solved][1.6.4] Modify vanilla block/item

[chiyin00]

How could I modify a vanilla block/item? I had tried to modify the class file. But it doesn't work after I pack the mod.

e.g. Make a dirt Block drop a diamond

[chiyin00]

I have tired to use the method idDropped. But after I recompile it, it doesn't works

[Zer0HD2]

There's also a pretty nifty search bar on these forums... you could, I don't know, find the 10 or so people who have asked this exact question before you and read the answers given to them. Which, by the way, are almost always the answer diesieben07 gave above.