@Test
 public void putIfAbsent() {
   HazelcastClient hClient = getHazelcastClient();
   IMap<String, String> map = hClient.getMap("putIfAbsent");
   String result = map.put("1", "CBDEF");
   assertNull(result);
   assertNull(map.putIfAbsent("2", "C"));
   assertEquals("C", map.putIfAbsent("2", "D"));
 }
 @Test
 public void putIfAbsentWithTtl() throws InterruptedException {
   HazelcastClient hClient = getHazelcastClient();
   IMap<String, String> map = hClient.getMap("putIfAbsentWithTtl");
   String result = map.put("1", "CBDEF");
   assertNull(result);
   assertNull(map.putIfAbsent("2", "C", 100, TimeUnit.MILLISECONDS));
   assertEquals(2, map.size());
   assertEquals("C", map.putIfAbsent("2", "D", 100, TimeUnit.MILLISECONDS));
   Thread.sleep(100);
   assertEquals(1, map.size());
 }