launch delay(5000) // This runs on the main server thread after 5 seconds player.sendMessage(Text.literal("5 seconds have passed!"))
@Serializable data class EnergyComponent(var amount: Int, val max: Int) // Instantiate val battery = EnergyComponent(100, 500) val copy = battery.copy(amount = 200) // Immutable copy with change Need to run code after 5 seconds without blocking the game thread?
Clone the template and replace println("Hello World!") with player.sendMessage() . kotlin for fabric
“But isn’t Kotlin slower?” – Not meaningfully. Kotlin compiles to the same bytecode as Java. In fact, inline functions and smart casts can produce more optimized bytecode than equivalent Java.
player?.world?.setBlockState(pos, state) // Safe call chain If player or world is null, nothing happens. No crash. Add a helper to check if a block is exposed to sky: launch delay(5000) // This runs on the main
Let’s look at real modding scenarios. 1. Null Safety (Goodbye Crashes) Java:
| Feature | Benefit for Modders | | :--- | :--- | | | Forget @Nullable annotations. The compiler enforces null safety, eliminating NullPointerException crashes. | | Data Classes | One line of code for ItemStack , BlockPos , or custom component holders. | | Extension Functions | Add methods to PlayerEntity or World without inheritance or wrappers. | | Coroutines | Write asynchronous tasks (e.g., HTTP requests, delayed actions) without callback hell. | | Immutability | val over var encourages thread-safe, predictable code. | Setting Up a Kotlin Fabric Project Fabric does not natively support Kotlin, but the community maintains Fabric Language Kotlin (FabricLKotlin) . Think of it as the Kotlin runtime for Fabric. Step 1: Use the Template The easiest way is to use the official template: Kotlin compiles to the same bytecode as Java
// The magic ingredient modImplementation("net.fabricmc:fabric-language-kotlin:1.10.0+kotlin.1.9.0") Tell Fabric to use the Kotlin language adapter: