title: Accessing Hashmap from multiple threads without synchronization
body: <p>I have a HashMap that I need multiple threads to access. My design is such that each thread will be reading and writing to its own entry in the map: the same map, but no two threads work on the same entry. No one thread will ever need to iterate over the map or call <code>size()</code>. So my question is: do I have to synchronize on the Hashmap or may I just use it with confidence that it will never throw a ConcurrentModificationException? My obvious worry is that synchronizing will create a huge bottleneck.</p>