var assetsDir = new File(gameDir, "assets");

将资源目录改为.minecraft的assets目录

var indexDir = new File(assetsDir, "indexes");
if (!indexDir.exists()) {
    indexDir.mkdir();
}

var objectDir = new File(assetsDir, "objects");
if (!objectDir.exists()) {
    objectDir.mkdir();
}

创建indexesobjects目录

public class AssetObject {
    private final String hash;
    private final long size;

    public AssetObject(String hash, long size) {
        this.hash = hash;
        this.size = size;
    }

    public String getHash() {
        return hash;
    }

    public long getSize() {
        return size;
    }
}

创建AssetObject

var indexContent = IOUtils.toString(new URL(gameJson.get("assetIndex").getAsJsonObject().get("url").getAsString()), StandardCharsets.UTF_8);
var indexObject = gson.fromJson(indexContent, JsonObject.class);
for (Map.Entry<String, JsonElement> objects : indexObject.get("objects").getAsJsonObject().entrySet()) {
    var assetObject = gson.fromJson(objects.getValue(), AssetObject.class);
    var objectIndexDir = new File(objectDir, assetObject.getHash().substring(0, 2));
    if (!objectIndexDir.exists()) {
        objectIndexDir.mkdir();
    }
    var objectIndexFile = new File(objectIndexDir, assetObject.getHash());

    if (!objectIndexFile.exists()) {
        FileUtils.writeByteArrayToFile(objectIndexFile, IOUtils.toByteArray(new URL("https://resources.download.minecraft.net/" + assetObject.getHash().substring(0, 2) + "/" + assetObject.getHash())));
    }
}

遍历出所有资源,下载,路径hash前两位/hash全部,连接为https://resources.download.minecraft.net/

之后把assetIndex改为gameVersion

FileUtils.writeStringToFile(new File(indexDir, gameVersion + ".json"), indexContent, StandardCharsets.UTF_8);

assetsIndex的内容保存到indexes