uninitialized final variable!

[Lalaka Jeerasinghe]

Final Variables
Declaring a variable with the final keyword makes it impossible to reinitialize that variable once it has been initialized with an explicit value (notice we said explicit rather than default). For primitives, this means that once the variable is assigned a value, the value can't be altered. For example, if you assign 10 to the int variable x, then x is going to stay 10, forever.

K&B BOOK PG 57.

So does this mean that without initialization, the final variable in the above source gets the value 0 assigned automatically, since its the default for primitves(here int), and receives the ability to modify it later

class TestKB{
public static void main(String arg[]){
     final int a;
     a=10;
     System.out.println(a);
}
}

prints out a's value as 10.


But this

class TestKB{
public static void main(String arg[]){
     final int a = 1;
     final int b;
     b=2;
     int x=0;
   switch(x) {
       case a:
       case b:
   }
}}

Is this valid.... Compile error is there.
If the value 10 was assigned in the first coding sample. why does the switch statement requires to initialize the variable at the same time??

Compile error :- TestKB.java:9: constant expression required
case b:
^

[Prithvi Sehgal]

Hello,

The reason is that in switch statements ,the case should always be a compile time constant and in your case
b is not a compile time constant. To have a look about what is a compile time constant, you can have a look
at my blog and you will find a link to a very good discussion about compile time constants.

Check ThisDiscussionOnRanch


HTH,

[Sunny Bhandari]

I would like to add that the case argument must be of type int but since char, byte, short are compatible with int, they also work fine.

But you may not use long for case argument.

[Lalaka Jeerasinghe]

Thanks Prithiv!!

The link i followed was really helpful
Thanks for pointing it out.

https://coderanch.com/t/454384/java/java/compile-time-constant

[Prithvi Sehgal]

Dear Lalaka,

You are very welcome.

Happy Preparation,