Anyone know the interface "serializable"? and what is this for?
Serializable is an empty interface (a.k.a marker interface) that is used to "mark" a class as serializable. This means that the state of that class's object can be stored into a file which can be used later either by the same machine or a different machine even after the running machines JVM is shut down. This basically persists the object state across programs and machines. I hope this clears your doubt. :)
It makes that java class "savable"