HashMap and concurrency- different keys

Question

Say I have a hash map and multiple threads. If I have a synchronized method that adds to the hash map, how would I make it possible that two different threads can put differ

Answer 1

The easiest answer is to use a ConcurrentHashMap, which does exactly what you're looking for.

If you can't do that (I see you edited your post after I answered), then you'll have to duplicate the same thing that ConcurrentHashMap does. No, simply synchronizing the method of a HashMap will not allow two threads to add a key-value pair at the same time, they have to wait and go one at a time.