final variable

[Calanthe Wei]

see the code below:

<font size=2.5>public class FinalTest
{
    public static void main(String argv[]) 
    {
        System.out.println("final = " + Loaded.x );
        // The static initializer of Loaded in the following line :
        System.out.println("non-final = " + Loaded.y );
    }
}
    
class Loaded
{
    static 
    {
        System.out.println("\tInitialization of Loaded");
    }
    
    public static final String x = "final";
    
    public static String y = "non-final"; // add final here
}

the result is:
final = final
Initialization of Loaded
non-final = non-final
And when I add change a little bit in the last sentence, like
public static final String y = "non-final";
the result is:
final = final
non-final = non-final
I am a little confused about these two results, can someone
explain it to me? thanks
regds,
Calanthe

[This message has been edited by Marilyn deQueiroz (edited November 10, 2001).]

[William Brogden]

I don't understand where the problem is - since your program does not attempt to change the value of a final variable, the modifier has no effect.
Bill

[Fei Ng]

Originally posted by William Brogden:
I don't understand where the problem is - since your program does not attempt to change the value of a final variable, the modifier has no effect.
Bill

William, it is the output. On the second output the
"Initialization of Loaded" is gone.
the result is:
final = final
Initialization of Loaded
non-final = non-final
And when I add change a little bit in the last sentence, like
public static final String y = "non-final";
the result is:
final = final
non-final = non-final

[Nain Hwu]

One of reasons that triggers a class initialization is
when a static field declared by it is used and the reference
is not a compile time constant. Reference to a comiple-time
constant is resolved at compile time. Its use never cause initialization. (see JLS 12.4.1)

The declaration
public static final String x = "final";
makes x a compile-time constant. (see JLS 15.28)
That's why

System.out.println("final = " + Loaded.x );

does not cause initialization of class Loaded.
It's the next statement

System.out.println("non-final = " + Loaded.y ); 

that causes the initialization.
Similarly, when you change

 public static String y = "non-final"; 

to static final, it becomes a compile-time
constant. So, class Loaded is not initialized.

[Maulin Vasavada]

hi all,
it was a useful tip.
thanks
maulin

[Fei Ng]

agree with Maulin, Vasavada..

hehehe..

[Calanthe Wei]

Thank you guys.
I got it.
Calanthe