Java ConcurrentHashMap

Sample ConcurrentHashMap

The ConcurrentHashMap class in Java is a thread-safe implementation of the Map interface. This means it allows multiple threads to access and modify its contents concurrently without throwing ConcurrentModificationException errors.

Here are some key points about ConcurrentHashMap:

• Thread-safety: It achieves thread-safety through a technique called concurrency control. This involves using mechanisms like locks or compare-and-swap (CAS) operations to ensure that only one thread can modify the map at a time, preventing data corruption.
• Performance: Compared to the traditional HashMap, ConcurrentHashMap has slightly lower performance due to the overhead of concurrency control. However, it is still a good choice for most multi-threaded applications due to its thread-safety guarantees.
• Use cases: It is ideal for situations where multiple threads need to access and modify a shared map concurrently, such as: Caching data Implementing concurrent data structures Managing shared resources in multi-threaded applications

Without concurrent ConcurrentHashMap, we will get exception

java.util.ConcurrentModificationException

public class ConcurrentHashMapSample {

    public static void main(String[] args) {

        Map<String, Object> animals = new HashMap<String, Object>();
        animals.put("penguin", 1);
        animals.put("flamingo", 2);
        animals.put("tiger", 3);

        for(Map.Entry<String, Object> entry: animals.entrySet()) {
            if (entry.getKey().equals("tiger")) {
                animals.remove("tiger");
            }
        }

        for(Map.Entry<String, Object> entry: animals.entrySet()) {
            System.out.println("==key:"+entry.getKey());
        }

    }
}        

With ConcurrentHashMap

public class ConcurrentHashMapSample {

    public static void main(String[] args) {

        Map<String, Object> animals = new ConcurrentHashMap<>();
        animals.put("penguin", 1);
        animals.put("flamingo", 2);
        animals.put("tiger", 3);

        for(Map.Entry<String, Object> entry: animals.entrySet()) {
            if (entry.getKey().equals("tiger")) {
                animals.remove("tiger");
            }
        }

        for(Map.Entry<String, Object> entry: animals.entrySet()) {
            System.out.println("==key:"+entry.getKey());
        }

    }
}        

The code run success and we get the result

==key:penguin

==key:flamingo

--end