variable declaration

[nishesh chouhan]

can anyone tell me what all method declaration are valid amongs t the follpw ing
abstract int i;
a) abstract int i;
b] final int i;
c] final volatile int i;
d] public transient final i;
e] protected static final int i;
I think none is right b'coz when we declare final we need t o
intialize the variable there only
but why cant the variable be declared as abstract
???

[Sean Casey]

You don't need to intialize a final variable at time of declaration. It is called a blank final, but it needs to be initialized before it is used. The keyword abstract pertains to methods and classes. It implies that the method or class is incomplete.

[Ravindra Mohan]

Hi Everyone,
Please refer to the folowing code for my
clarification on the querry posted:

a) abstract int i;    // Illegal, a variable CAN NOT be declared as abstract

b] final int i;       // perfectly fine, defination can be made 
// later, but must be done before using the variable "i". 
// FINAL specifier states that it's value once defined CAN NOT be changed. 

c] final volatile int i;  // perfectly fine, telling the compiller that the variable 
// should not be optimised for efficiency. This declaration 
// is genarally done in multi-threading situations
// where the same variables are shared and may lead to some
// unexpected results. FINAL specifier states that it's value once defined CAN NOT be changed. 
   
d] public transient final i;  // perfectly fine, imforming the 
// compiler that the variable "i" SHOULD NOT be "serialized" 
// i.e., it state should NOT BE made persistent while the object
// is being serialised. PUBLIC access specifier indicates that 
// the variable can be accessed any where else. FINAL specifier states that it's value once defined CAN NOT be changed. 

e] protected static final int i; // perfectly fine, STATIC specifier indicates that the variable is class variable and
// not an instance variable. PROTECTED specifier indicates that the varible is accessbile in the subclass of class in which they
// are declared. FINAL specifier states that it's value once defined CAN NOT be changed. 

Hope this clarifies, so (b),(c),(d) and (e) are correct answers.
Ravindra Mohan.
[This message has been edited by Ravindra Mohan (edited May 08, 2001).]

[Sean Casey]

Ravindra,
c is incorrect since volatile can't be used with the final keyword. Try to compile it yourself. d is incorrect since there is no reference type. Try to compile them yourself. Transient can't be used with the final keyword either. At least that's what my compiler tells me.

[Lam Thai]

Originally posted by Sean Casey:
Ravindra,
c is incorrect since volatile can't be used with the final keyword. Try to compile it yourself. d is incorrect since there is no reference type. Try to compile them yourself. Transient can't be used with the final keyword either. At least that's what my compiler tells me.

Hi Sean,
You are right - final and volatile won't go together.
However the combination of transient and final is fine. The reason you got a compilation error is because the declaration shown in the question was wrong - try this:
public transient final int i = 10;
Take care,
- Lam -

[Ravindra Mohan]

Hi Guys,
Oops a correction from my earlier post, A VOLATILE variable cannot be declared as FINAL. I ran a code and the compiler told me the answer. I then looked for the same in the JLS which confirmed me the same. Please refer to JLS �8.3.1.4 volatile Fields at http://java.sun.com/docs/books/jls/second_edition/html/classes.doc.html#36930
where this is clearly indicated :

A compile-time error occurs if a final variable is also declared volatile.

Hope this clears the issue.
Ravindra Mohan.

[Stevie Kaligis]