@Override
    public R get(Object key) {
        if (key instanceof Integer) {
            int n = (Integer) key;
            return get(n);
        }
        return super.get(key);
    }
@Test
    public void lookupWithBogusKeyType() {
        assertNull(a.get(null));
        // don't inline, otherwise some IDEs will immediately complain about the wrong key type
        Object badKey = "foo";
        assertNull(a.get(badKey));
        badKey = this;
        assertNull(a.get(badKey));
    }