Question

I need to map objects inside Servlet. Is ConcurrentHashMap a reliable choice to use? Will all requests get requested object from map or will there be failures?

public class MyServlet extends HttpServlet {

    private Map<String, Object> map = new ConcurrentHashMap<String, Object>();

    public void doGet(HttpServletRequest request, HttpServletResponse response) {
        // use map
        map.get("myObjectName");
    }

}

Answer 1

The purpose of a ConcurrentHashMap is to allow retrieval without locking. It is suitable for multi-threaded programs that have lot of reads and very few writes.

You wrote

Objects are not modifided after servlet init. – newbie

If by that you mean that the map does not change after servlet initialization, then you don’t need a ConcurrentHashMap at all. You can use plain old HashMap. Even better would be to convert it to a non-modifiable map by using Collections.unmodifiableMap.