ConcurrentHashMap vs ReentrantReadWriteLock based Custom Map for Reloading

Question

Java Gurus,

Currently we have a HashMap which is being read frequently and modified occasionally and w

Answer 1

It seems you are not sure as to how what Peter Lawrey suggests can be implemented. It could look like this:

class YourClass {
    private volatile Map map;

    //constructors etc.

    public void reload() {
        Map newMap = getNewValues();
        map = Collections.unmodifiableMap(newMap);
    }
}

There are no concurrency issues because:

• The new map is created via a local variable, which by definition is not shared - getNewValues does not need to be synchronized or atomic
• The assignement to map is atomic
• map is volatile, which guarantees that other threads will see the change