@Test
public void testComputeDataIfAbsent() {

    AtomicLong cnt = new AtomicLong();
    for (int i = 0; i < 10; i++) {
        Integer res = (Integer) dataStorage.computeDataIfAbsent(0, () -> {
            cnt.incrementAndGet();
            return 42;
        });
        assertEquals(42, res.intValue());
    }
    assertEquals(1, cnt.intValue());
}