what is Serialiable class for ?

[jimmy6]

why some class need to implement Serialiable class? what is Serialiable class? why need it? I saw this in hibernate's persistance class that implements this class but i do not know why need this. I do not understand those low level thing in java. Help pls?

[ray326]

A class needs to be serializable for it to exist somewhere other than in memory. It has to be serialized to pass it over the network or to be shared across multiple servers.

[sjalle]

Serializable is an interface that "defines" two methods, readObject and writeObject.
I write "defines" because you will not get a compilation error if you declare a
class as serializable without implementing these two;

private void writeObject(java.io.ObjectOutputStream out)
     throws IOException
 private void readObject(java.io.ObjectInputStream in)
     throws IOException, ClassNotFoundException;

As it works; the writeObject method writes the data to the stream and readObject
must be designed to read the same data, in the same sequence, back again.