### Question:
CacheFactory { public static Cache getInstance() { return instance; }  static Cache getInstance();  }### Answer:
@Test public void testEval() { Cache cache = CacheFactory.getInstance(); cache.del("k1", "k2", "k3"); cache.sadd("k1", "v1", "v2"); cache.sadd("k2", "v3", "v4"); assertEquals(0L, cache.scard("k3").longValue()); }