Generic Y Combinator in Java

YFact.java

//based on code from http://www.arcfn.com/2009/03/y-combinator-in-arc-and-java.html

class YFact {
    // T function returning a T
    // T -> T
    public static interface Func<T> {
        T apply(T n);
    }

    // Higher-order function returning a T function
    // F: F -> (T -> T)
    private static interface FuncToTFunc<T> {
        Func<T> apply(FuncToTFunc<T> x);
    }

    //Next comes the meat. We define the Y combinator, apply it to the factorial input function, and apply the result to the input argument. The result is the factorial.
    public static <T> Func<T> Y(final Func<Func<T>> r) {
        return (new FuncToTFunc<T>() {
            public Func<T> apply(final FuncToTFunc<T> f) {
                return f.apply(f);
            }
        })
                .apply(
                        new FuncToTFunc<T>() {
                            public Func<T> apply(final FuncToTFunc<T> f) {
                                return r.apply(
                                        new Func<T>() {
                                            public T apply(T x) {
                                                return f.apply(f).apply(x);
                                            }
                                        });
                            }
                        });
    }

    public static void main(String args[]) {
        System.out.println(
                // Y combinator
                Y(
                        // Recursive function generator
                        new Func<Func<Integer>>() {
                            public Func<Integer> apply(final Func<Integer> f) {
                                return new Func<Integer>() {
                                    public Integer apply(Integer n) {
                                        if (n == 0) return 1;
                                        else return n * f.apply(n - 1);
                                    }
                                };
                            }
                        }

                ).apply(
                        // Argument
                        Integer.parseInt(args[0])));
    }
}