public CallSession destroyPhoneSession(String id) {
public synchronized CallSession destroyPhoneSession(String id) {
    public CallSession destroyPhoneSession(String id) {        CallSession session = sessionMap.remove(id);        if(session != null) {            Collection<CallSession> sessions = userSessionMap.get(session.getUsername());            // should never be null            sessions.remove(session);            // Remove the map if there are nolonger any session for this user            if(sessions.size() == 0) {                userSessionMap.remove(session.getUsername());            }        }        return session;    }