public static <T> Supplier<T> memoizeConcurrent(Supplier<T> onceSupplier) {
        return new ConcurrentMemoizingSupplier<>(onceSupplier);
    }
@Test(expected = NullPointerException.class)
    public void when_memoizeConcurrentWithNullSupplier_then_exception() {
        Supplier<Object> supplier = () -> null;
        memoizeConcurrent(supplier).get();
    }