gistfile1.java

public final class AnF implements F<String, Integer> {
    public Integer f(String s) {
        return Integer.parseInt(s);
    }
}

public interface AnotherF extends F<String,Integer> {
    static AnotherF _ = new AnotherF() {
        public Integer f(String s) {
            return Integer.parseInt(s);
        }
    };
}

public final class x {
    public static void main(String[] args) {
        List<String> someList = Arrays.asList("1", "2", "3");
        List<Integer> anF = Lists.transform(someList, toFunction(new AnF()));
        List<Integer> anotherF = Lists.transform(someList, toFunction(AnotherF._));
    }
}