Comparision

[Manish Singhal]

Please let me know what is the output of the following code (with explanation...why and how)
public class Compare {
public static void main(String args[]) {
int x = 10, y;
if(x < 10) <br /> y = 1;<br /> if(x>= 10) y = 2;
System.out.println("y is " + y);
}
}

Regards,
Manish Singhal

[Jane Griscti]

Hi Manish,
The code won't compile. 'y' is an instance variable; which are not initialized to any default values. Given the code, we know that 'y' will be initialized at some point but the compiler doesn't; hence the error.
Hope that helps.

------------------
Jane

[bill bozeman]

It won't compile. Variables inside methods have to be initialized before you can use them. You can't initialize them inside if blocks because the compiler doesn't know whether or not that if block will execute. If this was a member variable, outside of the method (it would have to be static also since main is a static method) then it would be initialized to 0 and the code would work and give you "y is 2".
Bill

[Jon Aryan]

Jane ... "y" is a local variable ... not an instance variable ! ... may be a typo rite ??
Aryan.

[Manish Singhal]

Thanks to all of you.
I knew that we have to initialize local variable before using it but was confused and thought that " if " construct will initialize it.
regards,
Manish

[Stephen Pride]

But ... If the code were this instead:

public class Compare {
  public static void main(String args[]) {
    int x = 10, y;
    if (x < 10)
      y = 1;
    else
      y = 2;
    System.out.println("y is " + y);
  }
}

Then it will compile without any errors. So even though "y" was not initially initialized, the compiler "knows" it will be before it is used.
Regards,
SP

[Manish Singhal]

Thanks Stephen
regards,
Manish

[Bin Zhao]

So,the compiler is so smart that it can judge whether y can be
initialized.But if in another situation,how can we judge if the compiler can make correct decision?

[Jane Griscti]

Hi John ...
You're right ... and I knew that when I posted! Thanks for correcting my mistake
------------------
Jane