1.8 Vanilla to/from Bukkit 1.8 - Java Code

package ovh.roro;

import com.google.gson.Gson;
import com.google.gson.JsonObject;
import net.minecraft.server.v1_8_R3.Block;
import net.minecraft.server.v1_8_R3.Item;
import org.bukkit.Material;

import java.io.PrintWriter;

public class ExportMaterials {

    public static void run() {
        try {
            JsonObject bukkitToVanilla = new JsonObject();
            JsonObject vanillaToBukkit = new JsonObject();

            for (Material material : Material.values()) {
                String bukkit = material.name();
                String vanilla = null;
                Item item = Item.getById(material.getId());

                if (item != null) {
                    vanilla = Item.REGISTRY.c(item).a();
                }

                if (vanilla == null) {
                    Block block = Block.getById(material.getId());

                    if (block == null) {
                        continue;
                    }

                    vanilla = Block.REGISTRY.c(block).a();
                }

                bukkitToVanilla.addProperty(bukkit, vanilla);
                vanillaToBukkit.addProperty(vanilla, bukkit);
            }

            Gson gson = new Gson();

            try (PrintWriter writer = new PrintWriter("bukkit_to_vanilla.json")) {
                gson.toJson(bukkitToVanilla, writer);
                writer.flush();
            }

            try (PrintWriter writer = new PrintWriter("vanilla_to_bukkit.json")) {
                gson.toJson(vanillaToBukkit, writer);
                writer.flush();
            }
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }
}