final variable declaration

[Pavan Chillara]

Hi,

I have declared one of my class variables as final and in the method defined in that class i declared one of my method variables as final.Here i am getting compilation error when i am trying to change the both the variables.
But I have defined one more method in the same class with the method argument as final variable.But it wont be showing any compilation error when i am trying to change the value.

Can anyone explain me the reason why is this happening.

Regards,

[Keith Lynn]

Can you show the code?

[Pavan Chillara]

Hi,

My Code is as follows

 
package mapack.subclass;
 
class Example {
    final int i = 10;
 
    int j = 20;
 
    int A(final int k) {
        int j = k + 1;
        System.out.println("j    " + j);
        return j;
    }
 
    void X() {
        final int n = 0;
        System.out.println("This is Example");
        while (true) {
 
            n = A(j); // Compilation Error
            System.out.println("n   " + n);
            j++;
            if (n == 25)
                break;
        }
    }
 
}
 
public class FinalExample extends Example {
 
    public FinalExample() {
        super();
    }
 
    public static void main(String[] args) {
 
        new Example().X();
 
    }
 
}
 

 

[Keith Lynn]

I don't see where you're trying to change the final parameter.

[Rahul Bhattacharjee]

I do not see any final variable changes.
And what kind of compilation failure are you getting.

final int j = 10;

int k = j + 1;

In this the final variable is not getting changed.

[satishkumar janakiraman]

Hi,

Yes it would return a compilation error. The value of j is changed to 21 inside the function A(final int k) and returns the new value and assigns it to the final variable n in method X().

Final variable values cannot be changed. It acts like a constant.

bye for now
sat

[Tony Morris]

Final variables do not act like constants

[Joanne Neal]

Originally posted by satishkumar janakiraman:
The value of j is changed to 21 inside the function A(final int k)

No it's not. The j that you change in A() is a local variable with the same name as the instance variable. Try changing

int j = k + 1;

to

j = k + 1;

[Abdul Rehman]

Originally posted by Pavan Chillara:
void X() {
final int n = 0; // Statement (1)
System.out.println("This is Example");
while (true) {

n = A(j); // Compilation Error --> Statement (2)
System.out.println("n " + n);
j++;
if (n == 25)
break;
}
}

}

At (1), you definitely assign "n" the value 0, which is a final variable. At (2), you are trying to re-assign a value to "n", a final variable, which already is definitely assigned a value at (1). This is the error in your program; its not possible to change the value of 'n' once you have definitely assigned it a value.
Hope clarified the confusion.

Regards,
Abdul Rehman.
[ November 23, 2006: Message edited by: Abdul Rehman ]