public void clear() {
        for (Section s : sections) {
            s.clear();
        }
    }
@Test
    public void testClear() {
        ConcurrentLongPairSet map = ConcurrentLongPairSet.newBuilder()
                .expectedItems(2)
                .concurrencyLevel(1)
                .autoShrink(true)
                .mapIdleFactor(0.25f)
                .build();
        assertTrue(map.capacity() == 4);

        assertTrue(map.add(1, 1));
        assertTrue(map.add(2, 2));
        assertTrue(map.add(3, 3));

        assertTrue(map.capacity() == 8);
        map.clear();
        assertTrue(map.capacity() == 4);
    }