import java.util.concurrent.ConcurrentHashMap; ConcurrentHashMap<String, Integer> map = new ConcurrentHashMap<>(); map.put("key1", 1); map.put("key2", 2); map.put("key3", 3); int value = map.get("key2"); System.out.println(value); import java.util.concurrent.ConcurrentLinkedQueue; ConcurrentLinkedQueue<String> queue = new ConcurrentLinkedQueue<>(); queue.offer("item1"); queue.offer("item2"); queue.offer("item3"); String item = queue.poll(); System.out.println(item); import java.util.concurrent.atomic.AtomicInteger; AtomicInteger counter = new AtomicInteger(0); int value = counter.incrementAndGet(); System.out.println(value);