ArrayList problem ...

[S Majumder]

Below is my cod :

class Animal extends ArrayList<Integer>
{
	
	
}

I have written it in the eclipse & the IDE showing one warning without error like this :

The serializable class Animel does not declaired a static final serialVersionUID field of type long.


but when I modified and add the public static final long serialVersionUID = 0; that warn vanishes .


Can anybody explain why this is happening ?

regards,
S

[Seetharaman Venkatasamy]

s begri wrote:Below is my cod :

class Animal extends ArrayList<Integer>
{
	
	
}

but when I modified and add the public static final long serialVersionUID = 0; that warn vanishes .
Can anybody explain why this is happening ?

better to modify the public access modifier to private. infact, ArrayList implements Serializable interface, so your Animal is a Serializable.

why we need to declare serialVersionUID explicitly?

from Javadoc:

The serialization runtime associates with each serializable class a version number, called a serialVersionUID, which is used during deserialization to verify that the sender and receiver of a serialized object have loaded classes for that object that are compatible with respect to serialization. If the receiver has loaded a class for the object that has a different serialVersionUID than that of the corresponding sender's class, then deserialization will result in an InvalidClassException. A serializable class can declare its own serialVersionUID explicitly by declaring a field named "serialVersionUID" that must be static, final, and of type long:

ANY-ACCESS-MODIFIER static final long serialVersionUID = 42L;


If a serializable class does not explicitly declare a serialVersionUID, then the serialization runtime will calculate a default serialVersionUID value for that class based on various aspects of the class, as described in the Java(TM) Object Serialization Specification. However, it is strongly recommended that all serializable classes explicitly declare serialVersionUID values, since the default serialVersionUID computation is highly sensitive to class details that may vary depending on compiler implementations, and can thus result in unexpected InvalidClassExceptions during deserialization. Therefore, to guarantee a consistent serialVersionUID value across different java compiler implementations, a serializable class must declare an explicit serialVersionUID value. It is also strongly advised that explicit serialVersionUID declarations use the private modifier where possible, since such declarations apply only to the immediately declaring class--serialVersionUID fields are not useful as inherited members.

[S Majumder]

Thanks Seetharaman Venkatasamy .
But the problem is I cannot make the Animal class as private .


Is there any other option ?


regards,
S

[Seetharaman Venkatasamy]

s begri wrote:
But the problem is I cannot make the Animal class as private .

you can not do that. I was mentioned to make the static serialVersionUID as private