About Observer pattern

Who has the experience with java.util.Observer and java.util.Observable ? Or Please help with 2nd parameter of method update(Observable o,Object arg)?
[165 byte] By [yuanmengyuan2a] at [2007-9-28 9:13:47]
# 1
If you read the API docs you'd see that the 2rd parameter is the message or event that has occurred. The first parameter is the source (i.e. the thing being observed); the 2nd parameter is the event (i.e. what happened).
larsonaa at 2007-7-11 22:09:53 > top of Java-index,Other Topics,Patterns & OO Design...