Skiplist uses Comparable interface, and HttpSession does not implement it.

code/moya-beans/ejbModule/fi/codecrew/moya/beans/SessionMgmtBean.java

@@ -23,6 +23,7 @@ import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Map;
 import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentSkipListMap;
 import java.util.concurrent.ConcurrentSkipListSet;
 
@@ -54,7 +55,7 @@ public class SessionMgmtBean implements SessionMgmtBeanLocal {
 	}
 
 	private final ConcurrentSkipListMap<String, String> sessionUsers = new ConcurrentSkipListMap<String, String>();
-	private final ConcurrentSkipListSet<HttpSession> sessions = new ConcurrentSkipListSet<HttpSession>();
+	private final Set<HttpSession> sessions = Collections.newSetFromMap(new ConcurrentHashMap<HttpSession, Boolean>());
 
 	@SuppressWarnings("unused")
 	private static final Logger logger = LoggerFactory.getLogger(SessionMgmtBean.class);