Question

I am working on a existing web based application which uses static map to store data specific to the Application .

This is my code below which is responsible to store Data inside a ConcurrentHashMap as shown below .

public class MyClass 

    // Class variable
    private static Map<String, UserThread> usermap = new ConcurrentHashMap<String, UserThread>();  

// Inside a Method 
public void userData()
 {
 UserThread  userThread= usermap.get(getLoginId());
 if (userThread == null) {
 userThread = new UserThread();
 userThread.start();
 usermap.put(getLoginId(), userThread);
 }
}

The application is working fine , here my question is that , is this a valid code because can we store Data inside a static variable ?? (Here the Static ConcurrentHashMap contains data specific to the Application )

Answer 1

With static map, you would run into the risk of memory leak unless you are sure of the life cycle of each entry added to the map, i.e. who would be adding them, how long will the entries stay there and when will they be removed so that they can be claimed during GC. Otherwise, your application will use up the memory and will start throwing OOME.