public static <V> Builder<V> newBuilder() {
        return new Builder<>();
    }
@Test
    public void testConstructor() {
        try {
            ConcurrentLongHashMap.<String>newBuilder()
                    .expectedItems(0)
                    .build();
            fail("should have thrown exception");
        } catch (IllegalArgumentException e) {
            // ok
        }

        try {
            ConcurrentLongHashMap.<String>newBuilder()
                    .expectedItems(16)
                    .concurrencyLevel(0)
                    .build();
            fail("should have thrown exception");
        } catch (IllegalArgumentException e) {
            // ok
        }

        try {
            ConcurrentLongHashMap.<String>newBuilder()
                    .expectedItems(4)
                    .concurrencyLevel(8)
                    .build();
            fail("should have thrown exception");
        } catch (IllegalArgumentException e) {
            // ok
        }
    }