public static Key of(String key, ApplicationId appId) {
        return new StringKey(key, appId);
    }
@Test
    public void longKey() {
        Key longKey1 = Key.of(LONG_KEY_1, NetTestTools.APP_ID);
        Key copyOfLongKey1 = Key.of(LONG_KEY_1, NetTestTools.APP_ID);
        Key longKey2 = Key.of(LONG_KEY_2, NetTestTools.APP_ID);
        Key copyOfLongKey2 = Key.of(LONG_KEY_2, NetTestTools.APP_ID);
        Key longKey3 = Key.of(LONG_KEY_3, NetTestTools.APP_ID);

        new EqualsTester()
                .addEqualityGroup(longKey1, copyOfLongKey1)
                .addEqualityGroup(longKey2, copyOfLongKey2)
                .addEqualityGroup(longKey3)
                .testEquals();
    }