Java: What can and what can't be serialized?

Question

If the Serializable interface is just a Marker-Interface that is used for passing some-sort of meta-data about classes in java - I\'m a bit confused:

After reading t

Answer 1

What data may cause the NotSerializableException?

In Java, we serialize object (the instance of a Java class which has already implemented the Serializable interface). So it's very clear that if a class has not implemented the Serializable interface, it cannot be serialized (then in that case NotSerializableException will be thrown).

The Serializable interface is merely a marker-interface, in a way we can say that it is just a stamp on a class and that just says to JVM that the class can be Serialized.

How should I know that I am not supposed to add the implements Serializable clause for my class?

It all depends on your need.

1. If you want to store the Object in a database, you can serialize it to a sequence of byte and can store it in the database as persistent data.

2. You can serialize your Object to be used by other JVM working on different machine.

Answer 2

NotSerialisable exception is thrown when something in your serializable marked as serializable. One such case can be:

class Super{}
class Sub implements Serializable
{
Super super;

Here super is not mentioned as serializable so will throw NotSerializableException.

Answer 3

When you are talking about NotSerializableException it is throw when you want to serialize an object, which has not been marked as Serializable - that's all, although when you extend non serializable class, and add Serializable interface it is perfectly fine.

There is no data that can't be serialized.