ExampleLootModifier.java

package com.example.examplemod;

import net.fabricmc.fabric.api.loot.v3.LootTableEvents;
import net.minecraft.loot.LootPool;
import net.minecraft.loot.condition.RandomChanceLootCondition;
import net.minecraft.loot.entry.ItemEntry;
import net.minecraft.loot.provider.number.ConstantLootNumberProvider;
import net.minecraft.registry.RegistryKeys;
import net.minecraft.util.Identifier;

/**
 * Add extra loot drops to an existing loot table (vanilla or modded)
 * without overwriting it. LootTableEvents.MODIFY API (v3) is current
 * for 1.21.7 - 1.21.11.
 */
public final class ExampleLootModifier {

    private ExampleLootModifier() {}

    public static void register() {
        LootTableEvents.MODIFY.register((key, tableBuilder, source, registries) -> {

            // Only modify the loot table for "minecraft:blocks/stone"
            if (key.getValue().equals(Identifier.ofVanilla("blocks/stone"))) {

                LootPool.Builder pool = LootPool.builder()
                        .rolls(ConstantLootNumberProvider.create(1))
                        .with(ItemEntry.builder(ExampleMod.EXAMPLE_GEM))
                        .conditionally(RandomChanceLootCondition.builder(0.01f)); // 1% chance

                tableBuilder.pool(pool);
            }
        });
    }
}