@Command("say")
public void say(@Sender CommandSender sender,String message){
    System.out.println(sender.getSenderName()+": "+message);
}

SimpleCommandManager simpleCommandManager = new SimpleCommandManager();
MethodAnnotationCommand.getBuilder(simpleCommandManager)
        .addCommandHandler(this)
        .register();

simpleCommandManager.execute(testSender, "say hello!");