Question

If in a class I have a ConcurrentHashMap instance that will be modified and read by multiple threads I might define like this:

public class My Class {

    private volatile ConcurrentHashMap<String,String> myMap = new ConcurrentHashMap<String,String>();
...
}

adding final to the myMap field results in an error saying I can only use final or volatile. Why can it not be both?

Answer 1

volatile only has relevance to modifications of the variable itself, not the object it refers to. It makes no sense to have a final volatile field because final fields cannot be modified. Just declare the field final and it should be fine.