20 lines source takes an HOUR to compile:

class C<U> {
    U fu;
    C() {}
    C(C<U> other) { this.fu = other.fu; }
    C(U fu) { this.fu = fu; }

    static <U> C<U> m(C<U> src) { return new C<U>(src); }

    public static void main(String argv[]) {
        /* type inference is expected here: */
        C<String> c2 = m(new C<>(m(new C<>() )) );
        C<String> c3 = m(new C<>(m(new C<>(m(new C<>() )) )) );
        C<String> c4 = m(new C<>(m(new C<>(m(new C<>(m(new C<>() )) )) )) ); // Javac(1.04), ECJ(.71s)
        C<String> c5 = m(new C<>(m(new C<>(m(new C<>(m(new C<>(m(new C<>() )) )) )) )) ); // Javac(2.02s), ECJ(1.17s)
        C<String> c6 = m(new C<>(m(new C<>(m(new C<>(m(new C<>(m(new C<>(m(new C<>() )) )) )) )) )) ); // Javac(4.84s) ECJ(1.67s)
        C<String> c7 = m(new C<>(m(new C<>(m(new C<>(m(new C<>(m(new C<>(m(new C<>(m(new C<>() )) )) )) )) )) )) ); // Javac(14.99s) ECJ(10.82s)
        C<String> c8 = m(new C<>(m(new C<>(m(new C<>(m(new C<>(m(new C<>(m(new C<>(m(new C<>(m(new C<>() )) )) )) )) )) )) )) ); // Javac(79.62s) ECJ(134.64s)
        C<String> c9 = m(new C<>(m(new C<>(m(new C<>(m(new C<>(m(new C<>(m(new C<>(m(new C<>(m(new C<>(m(new C<>() )) )) )) )) )) )) )) )) ); // Javac(437s) ECJ(1305s)
        C<String> c10 = m(new C<>(m(new C<>(m(new C<>(m(new C<>(m(new C<>(m(new C<>(m(new C<>(m(new C<>(m(new C<>(m(new C<>()))))))))))))))))))); // 3600
    }
}

Each lines show how long it takes to compile it in seconds.
Time is about the same for original jdk8.0 and latest jdk8u20 and jdk9.