The ICommandManager interface is managing commands. So you can use it to get and execute commands.
You can get this from an IServer object.

Dieses Paket importieren

Link to dieses-paket-importieren

It might be required for you to import the package if you encounter any issues (like casting an Array), so better be safe than sorry and add the import.
import crafttweaker.command.ICommandManager;

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<th>
  Type
</th>
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<td>
  Map<String, <a href="/Vanilla/Commands/ICommand/">ICommand</a>\>
</td>
ZenGetter
commands

To add your own command, look at CommandEvent