How to Serialize a list in java?
All standard implementations of java.util.List already implement java.io.Serializable.
So even though java.util.List itself is not a subtype of java.io.Serializable, it should be safe to cast the list to Serializable, as long as you know it's one of the standard implementations like ArrayList or LinkedList.
If you're not sure, then copy the list first (using something like new ArrayList(myList)), then you know it's serializable.
As pointed out already, most standard implementations of List are serializable. However you have to ensure that the objects referenced/contained within the list are also serializable.
List is just an interface. The question is: is your actual List implementation serializable? Speaking about the standard List implementations (ArrayList, LinkedList) from the Java run-time, most of them actually are already.