combine putIfAbsent and replace with ConcurrentMap

Question

I have a usecase where I have to

• insert a new value if the key does not exist in the ConcurrentHashMap
• replace the old value with a new value if the key a

Answer 1

Your method seems thread safe. If you do not require the performance benefits of ConcurrentHashMap, consider using a regular HashMap instead and synchronize all access to it. Your method is similar to AtomicInteger.getAndSet(int), so it should be fine. I doubt there is an easier way to do this unless you're looking for a library call to do the work for you.