How to get furnace smelting result ? 1.16.5

[elllkere]

I saw a lot of codes with FurnaceRecipes.instance().getSmeltingResult(stack) but i dont have the definition of instance(). Is this an addon or whatever ?

Edited December 31, 2021 by elllkere

[Draco18s]

It's buried in a complex linq expression here, but example:
https://github.com/MinecraftForge/MinecraftForge/blob/72598871762a98c566689acddec539fa369ed86c/src/test/java/net/minecraftforge/debug/gameplay/loot/GlobalLootModifiersTest.java#L158-L164

What that linq expression does is check the itemstack passed to the method to see if it has a smelting result (161), and if so, return the result as a new stack (162), else return the original stack (163).