Check the Wiki to know how to use FlowUpdater and more information.

First, create a new VanillaVersion, specify arguments. Then build the version :

VanillaVersion version = new VanillaVersionBuilder().withName("1.15.2").withSnapshot(false).withVersionType(VersionType.VANILLA).build();

You have to put the version you want as parameter, you can set a snapshot if you want or latest. If you have specified "latest" to the version name, and that the version is a snapshot, replace false by true.

Then, instantiate a new FlowUpdater with FlowUpdaterBuilder#withXArguments#withAnotherArguemtn#build. Check the code for more information. The most of FlowUpdater objects are buildable: Build a new UpdaterOptions object: I'm enabling the re-extracting of natives at each update.

UpdaterOptions options = new UpdaterOptionsBuilder().withReExtractNatives(true).build();

FlowUpdater updater = new FlowUpdaterBuilder().withVersion(version).withUpdaterOptions(options).withLogger(someCustomLogger).build();

Don't forget to add a progress callback if you want to make a progress bar !

Finally, call the update function :

updater.update(new File("/your/path/"));

Replace false by true if you want to download the server Jar (useful for server installation program).

(You need to setup a vanilla updater !)

First, in your vanilla version builder, change the version type to VersionType.FORGE. Next, make a List of Mod objects.

List<Mod> mods = new ArrayList<>();
mods.add(new Mod("OneMod.jar", "sha1ofmod", 85120, "https://link/of/mod.jar"));
mods.add(new Mod("AnotherMod.jar", "sha1ofanothermod", 86120, "https://link/of/another/mod.jar"));

You can get a list of mods by providing a json link too : List<Mod> mods = Mod.getModsFromJson("https://url.com/launcher/mods.json");.

You can get mods from CurseForge too:

List<CurseFileInfos> modInfos = new ArrayList<>();
// project ID and file ID
modInfos.add(new CurseFileInfos(238222, 2988823));

You can get a list of curse mods by providing a json link too : List<CurseFileInfos> mods = CurseFileInfos.getFilesFromJson("https://url.com/launcher/cursemods.json");.

Then, build a forge version. For example, I will build a NewForgeVersion.

AbstractForgeVersion forgeVersion = new ForgeVersionBuilder(ForgeVersionBuilder.ForgeVersionType.NEW)
            .withForgeVersion("31.2.29")
            .withVanillaVersion(version)
            .withLogger(logger)
            .withProgressCallback(callback)
            .withCurseMods(modInfos)
            .withOptifine(new OptifineInfo("1.16.3_HD_U_G3", false)) // installing optifine for 1.16.3, false = not a preview
            .withUseFileDeleter(new ModFileDeleter(true, "jei.jar")) // delete bad mods, don't remove the file jei.jar if it's present in the dir.
            .withNoGui(true) // only for new forge version: true -> don't show the forge installer gui. false -> show the forge installer gui.
            .build();

Finally, set the Forge version corresponding to the wanted Forge version :

.withForgeVersion(forgeVersion);

That's all!

(You need to setup a vanilla updater !) In your vanilla version builder, change the version type to VersionType.MCP. Finally, set to vanilla version builder a MCP version :

.withMCP(new MCP("clientURL", "name", "clientSha1", "author", "serverURL", "serverSha1", 1215, 20525));

If you set an empty/null string in url and sha1 and 0 in size, the updater will use the default minecraft jar. Example on client-only mcp downloading :

.withMCP(new MCP("https://mighya.eu/resources/Client.jar", "f2c219e485831af2bae9464eebbe4765128c6ad6", "", "", 23005862, 210052));

You can get a MCP object instance by providing a json link too : .withMCP(MCP.getMCPFromJson("https://url.com/launcher/mcp.json"));. Nothing else to add :).

(You need to setup a vanilla updater !)

First, in your vanilla version builder, change the version type to VersionType.FABRIC. Next, make a List of Mod objects.

List<Mod> mods = new ArrayList<>();
mods.add(new Mod("OneMod.jar", "sha1ofmod", 85120, "https://link/of/mod.jar"));
mods.add(new Mod("AnotherMod.jar", "sha1ofanothermod", 86120, "https://link/of/another/mod.jar"));

You can get a list of mods by providing a json link too : List<Mod> mods = Mod.getModsFromJson("https://url.com/launcher/mods.json");.

You can get mods from CurseForge too:

List<CurseFileInfos> modInfos = new ArrayList<>();
// project ID and file ID
modInfos.add(new CurseFileInfos(238222, 2988823));

You can get a list of curse mods by providing a json link too : List<CurseFileInfos> mods = CurseFileInfos.getFilesFromJson("https://url.com/launcher/cursemods.json");.

Then, build a Fabric version.

FabricVersion fabricVersion = new FabricVersionBuilder()
            .withFabricVersion("0.10.8")
            .withVanillaVersion(version)
            .withLogger(logger)
            .withProgressCallback(callback)
            .withCurseMods(modInfos)
            .withUseFileDeleter(new ModFileDeleter(true, "sodium.jar")) // delete bad mods ; doesn't remove the file sodium.jar if it's present in the dir.
            .build();

Finally, set the Fabric version corresponding to the wanted Fabric version :

.withFabricVersion(forgeVersion);

That's all!

With FlowUpdater, you can download other files in your update dir! In your FlowUpdaterBuilder, precise an array list of ExternalFile (can be get by ExternalFile#getExternalFilesFromJson).

All json files can be generated by the FlowUpdaterJsonCreator !

With FlowUpdater, you can execute some actions after update, like patch a file, kill a process, launch a process, review a config etc... In your FlowUpdaterBuilder, precise a list of Runnable.

And all it's done !