public boolean putIfAbsent(long key1, long key2, long value1, long value2) {
        checkBiggerEqualZero(key1);
        checkBiggerEqualZero(value1);
        long h = hash(key1, key2);
        return getSection(h).put(key1, key2, value1, value2, (int) h, true);
    }
@Test
    public void testPutIfAbsent() {
        ConcurrentLongLongPairHashMap map = ConcurrentLongLongPairHashMap.newBuilder()
                .build();

        assertTrue(map.putIfAbsent(1, 1, 11, 11));
        assertEquals(map.get(1, 1), new LongPair(11, 11));

        assertFalse(map.putIfAbsent(1, 1, 111, 111));
        assertEquals(map.get(1, 1), new LongPair(11, 11));
    }