@Override
    public CompletionStage<V> getAsync(K key) {
        return cache.getAsync(key);
    }
@Test
    public void testGetAsync() throws Exception {
        cache.put(42, "foobar");

        Future<String> future = adapter.getAsync(42).toCompletableFuture();
        String result = future.get();
        assertEquals("foobar", result);
    }