I'm completely new to modding MC, but I have an idea I'd like to try out for a little racetrack I put together on a friend's server. I've looked around the different MC Forge tuts and think I have a basic understanding of how it works.

I'd like to make a simple sign block that when you right click it, it starts a timer, when you right click again, it stops, and a third time it resets the time. I know how to write the logic in Java, but what I'm wondering is if I can just inherit from the existing Sign block when creating my new block and then just override the right click method to do what I want it to. Along those same lines, would any block be extensible if you knew the name of the block?

You'll need to extend both the block (defining sign behavior) and the tile entity class (holding the current data for each instance of each timer-sign in the world). You need to wrap your head around the first idea, that there is one and only one block instance for each type of block (although "sign" might have both "wall" and "floor" subclasses).

 

A block by itself is allocated only 4 bits of data (called metadata) pertaining to each occurrence in the world. If your block needs more data at each occurrence, then it needs a tile entity (entry into a sparse data structure for the unusual blocks in the world).

 

Your block class will probably have all of the "thinking" logic, and your tile entity will hold the extra data with get & set methods.

there is one and only one block instance for each type of block (although "sign" might have both "wall" and "floor" subclasses).

 

Not sure how the classing is done, but at the block-ID point (its possible they use the same class, the way redstone (and a few other blocks) ore do), wall and floor signs are two different blocks.