Intializers

[K Sujit]

Hello All,

1) Can anybody tell why n the static initializer below, x++ gives compiler error while x =10 doesnot.

2) The current output is 15, I guess first the initliazer loop assigns x=10 then
static int x=15
assigns it 15.
But if I just say
static int x; Shouldn't it give me 0 as output instead of 10;


public class Test4 {

static{
x=10;
// x++; To avoid Compile err replace x by Test4.x;
}

static int x=15;

public static void main(String args[]){

System.out.println(x);


}
}

[Deepak Bala]

umm... the output i got was 11 after i corrected the forward referencing error. You need to move this statement above the static initializer:

static int x=15;

[K Sujit]

umm... the output i got was 11 after i corrected the forward referencing error. You need to move this statement above the static initializer:

static int x=15;

But x = 10 in the initializer works even if declaration of x is below the loop, only when it comes it to x++ it gives error.

Another issue is - why the compiler error goes away when x is replaced by Test4.x while x = 10 works in the same loop.

static{
x=10;
// x++; To avoid Compile err replace x by Test4.x;
}

[M Mistroni]

hello,
i also was wondering what wa shappening with your original post

then i found this comment here http://radio.javaranch.com/corey/2004/04/19/1082390724000.html


Same flow. Static variables and static blocks will be initialized when the class itself is loaded. IIRC they will also be executed in order from top to bottom.

HTH
marco

[Amirr Rafique]

Hi all

I couldn't digest the problem Can any one please explain

Thanks

[M Mistroni]

hello,
i'll try, anyone pls jump in if my explanation is incorrec

public class Test4 {

static{
x=10;
// x++; To avoid Compile err replace x by Test4.x;
}

static int x=15;

public static void main(String args[]){

System.out.println(x);
}
}

This will result in 15 being outputted. Why?

you are not instantiating any Test4 class. so compiler will read the value you have given to x at line 15.


And what if you replace the main method lik ethis ?

public static void main(String args[]){
Test4 t = new Test4();
System.out.println(t.x);
}

result will still be 15. because when instantiating an object, like i said in my prev post, Static variables and static blocks will be initialized when the class itself is loaded. IIRC they will also be executed in order from top to bottom.

if instead you write followign code,]

public class Test4 {

static int x=15;

static{
x=10;
// x++; To avoid Compile err replace x by Test4.x;
}



public static void main(String args[]){
Test4 t = new Test4();
System.out.println(t.x);


}
}

output will be 10 (the static block is 'executed' after the static variable has been defined.. remeber? top to bottom... )


Now, why uncommenting x++ will result in an error? if i m correct, it is for the same reason i have just explained. the variable x is defined after the static block

it is the same principle if you have a code like this

public class Test4 {
int i = j;
int j = 0;
..
}

if you replace the code with this:

public class Test4 {

static int x=15;

static{
x=10;
x++; //To avoid Compile err replace x by Test4.x;
}



public static void main(String args[]){
Test4 t = new Test4();
System.out.println(t.x);

}
}
code will compile an run fine.


// x++; To avoid Compile err replace x by Test4.x;
i cannot exactly explain this, unfortunately, but x in this cas will be seen as a class variable, (and i guess if you instead use x++, compiler will consider that an instance variable)...

hth, and if some one can clarify better the last issue (the one of the x++) i will appreciate it too

HTH
marco

[Vidhya Praba]

Hi,

Please refer the following link for forward referencing...

http://radio.javaranch.com/corey/2004/05/13/1084483439000.html

In summary, you can use x on the left hand side of the expression, but not on the right hand side, like x++, before it is declared.

Hope this helps...