Can somebody give me a comprehensive tutorial on how to make a custom stair block? I'm trying to make some sort of black sand and want all the smooth and stone versions like vanilla. I tried using code from various mods but it didn't work. I also tried just doing it myself but that didn't work. 

If you look at how vanilla implements it, you should see it's just as simple as creating a new `StairBlock` with the passed-in block supplier acting as a delegate to handle specific logic.

Yeah, I tried that (using the code for the oak stair) and renaming everything and it was full of errors. I checked to make sure there weren't any missing imports but nope. 

Error: 

src\main\java\net\the_typholorian\adventurous\init\AdventurousModBlocks.java:25: error: cannot find symbol
    public static final Block VOLCANIC_SANDSTONE_STAIRS = register("volcanic_sandstone_stairs", new StairBlock(VOLCANIC_SANDSTONE.defaultBlockState(), BlockBehaviour.Properties.copy(VOLCANIC_SANDSTONE)));
                                                                                                                                 ^
  symbol:   method defaultBlockState()
  location: variable VOLCANIC_SANDSTONE of type RegistryObject<Block>

Code:

public static final Block VOLCANIC_SANDSTONE_STAIRS = register("volcanic_sandstone_stairs", new StairBlock(VOLCANIC_SANDSTONE.defaultBlockState(), BlockBehaviour.Properties.copy(VOLCANIC_SANDSTONE)));

Do I need to make VolcanicSandstoneStairsBlock.class file?

If you are posting compiler errors, you are in the wrong place. You want a learning java forum.

 

You also don't understand how static initalisation or suppliers/deferred access works.

https://forums.minecraftforge.net/topic/122471-custom-boat-119/#comment-538014

https://forums.minecraftforge.net/topic/123532-crash-in-my-mods-fluid-setup-class-what-am-i-doing-wrong-here-solved/#comment-536786

or you can search to find the many other threads where this is discussed.

 

The correct code uses RegistryObjects properly - something like (untested pseudo code)

public static final DeferredRegister<Block> BLOCKS = ...
// Use a registry object
public static final RegistryObject<Block> VOLCANIC_SANDSTONE_STAIRS = BLOCKS.register("volcanic_sandstone_stairs",
  // deferred access to the constructor - you can't create the actual blocks until the RegisterEvent happens
  () -> new StairBlock(
      // VOLCANIC_SANDSTONE is a RegistryObject<Block>/Supplier<Block> so you use get() for the real Block.
      VOLCANIC_SANDSTONE.get().defaultBlockState(), 
      BlockBehaviour.Properties.copy(VOLCANIC_SANDSTONE.get()));

You will also need to make sure the VOLCANIC_SANDSTONE RegistryObject  is registered with the DeferredRegister before the stairs, otherwise those get()s will fail.

4 hours ago, warjort said:

You will also need to make sure the VOLCANIC_SANDSTONE RegistryObject  is registered with the DeferredRegister before the stairs, otherwise those get()s will fail.

Quick correction to warjort's example, you should be passing in a `Supplier<BlockState>` instead of the raw `BlockState` to support lazy loading such that the parameter is not reliant on registry order. Forge patches this constructor in.

5 minutes ago, ChampionAsh5357 said:

Quick correction to warjort's example, you should be passing in a `Supplier<BlockState>` instead of the raw `BlockState` to support lazy loading such that the parameter is not reliant on registry order. Forge patches this constructor in.

The original poster still needs the correct order to handle the block properties getting copied from the original block.

8 minutes ago, warjort said:

The original poster still needs the correct order to handle the block properties getting copied from the original block.

Fair point.