title: how to use concurrenthashmap correctly?
body: <p>say, I have a lot of read operations and a few write operations, and the object which will be placed in map is quite "heavy"-initialization of such object costs much memory/time,etc.</p>
  
  <p>how should I code to both utilize the high performance of concurrenthashmap and ensure a minimum cost of unnecessary initialization of those cached objects.</p>
  
  <p>sample code snippet is welcome and greatly appreciate!
  Thanks!</p>