Exception.getCause() returning null when trying to find the source of an exception

Question

why does System.out.println(e.getCause()); gives null? And can store whole HashSet collection like this?

private void saving() thro         


        

Answer 1

When an exception is chained, the getCause method is used to get the original cause. In this case, the exception was not chained from any other layer, hence getCause returns null. You should use e.printStackTrace() instead, to get the reason for the exception. Most likely, this would be because one or more keys/values in your HashSet are of a type that is not implementing java.io.Serializable.