Java Serialization - wrapper class

Question

I keep reading about serialization.. I understand how to serialize and deserialize custom objects. But I am not able to understand the rational behind why many classes in JAVA API implement Serialize by default.

• Michael Berry: Why shouldn't they? Surely it makes sense for these classes to implement Serializable rather than having to write all the logic manually everytime you want to serialize an object? It doesn't force you to serialize them, it just makes it easy to if you need to.
• user207421: 'So many' is meaningless. * Which* JDK classes implement Serializable that shouldn't, in your opinion?

Answer 1

Because there are cases which require the instances of these classes to be

• written on files
• sent via network (or to another JVM)
• represented by bytes

Answer 2

Because you can only serialize objects that are serializable. So if you have a field of a non serializable type, this field will not be serialized

• kushi: Do you meant to say a class having HAS-A relationship with a String field scenario? Ex An Emp class implementing Serializable having a field EmpName as String.When Emp is Serialized,EmpName will be serialized only because String implements Serializable
• Philipp Sander: yes! if an attribute type doesn't implement serializable, it cannot be serialized
• kushi: In that case,Object class can implement Serializable so that all objects in both API and custom classes will be automatically eligible for Serialization ryt??
• Philipp Sander: you may read this stackoverflow.com/questions/441196/…

Answer 3

Because these classes are meant to be stored in some persistent storage or transferred via network as stream of bytes.