Do we have anything like only during writing it will be synchronized else behave like ConcurrentHashMap?

Issue

• In our current code, when the route is starting it will load the data from table and populate hashmap and we use this data for further processing. Now we have a requirement to check the table for any changes in every 15mins and if any change noted then load the data in hashmap[during that time if any request/thread accessing hashmap should wait and the request should not fail]. Kindly suggest a solution. Please find the current route below.
  route

    from("timer:name?repeatCount=1")
        .setBody(simple("select URL from MSTR"))
        .to("jdbc:mysql-bank?outputType=SelectList")
        .process(populate hashmap...)

• If I use Collections.synchronizedMap() all read and write operations are synchronized. Do we have anything like only during writing it will be synchronized else behave like ConcurrentHashMap ?