sub-sub-commands on JCommander

SubSubCommands.java

public class SubSubCommands {

    public static void main(String[] args) {
        exec("a");
        exec("b");
        exec("a", "c");
        /*
            args: [a]
              program: "root a"
              command: [A]
            args: [b]
              program: "root b"
              command: [B]
            args: [a, c]
              program: "root a c"
              command: [C]
         */
    }

    static void exec(String... args) {
        JCommander root = JCommander.newBuilder()
                .programName("root")
                .build();

        addCommand(root, "A", "a");
        addCommand(root, "B", "b");
        addCommand(root, "C", "a", "c");

        root.parse(args);

        JCommander cmd = findCommander(root);
        System.out.printf("args: %s%n", Arrays.toString(args));
        System.out.printf("  program: \"%s\"%n", cmd.getProgramName());
        System.out.printf("  command: %s%n", cmd.getObjects());
    }

    private static void addCommand(JCommander root, Object object, String... commands) {
        JCommander current = root;
        for (int i = 0, n = commands.length - 1; i < n; i++) {
            JCommander next = current.getCommands().get(commands[i]);
            assert next != null;
            current = next;
        }
        String last = commands[commands.length - 1];
        current.addCommand(last, object);
        JCommander cmd = current.getCommands().get(last);
        cmd.setProgramName(Stream.concat(
                Stream.of(root.getProgramName()),
                Arrays.stream(commands)).collect(Collectors.joining(" ")));
    }

    private static JCommander findCommander(JCommander root) {
        JCommander current = root;
        while (true) {
            String cmd = current.getParsedAlias();
            if (cmd == null) {
                return current;
            } else {
                current = current.getCommands().get(cmd);
            }
        }
    }
}