CODEWITHSUNDEEP
javastaticinstancedeclarationinstantiation
wib
wib

Reputation: 425

declaring static variable after static initialzer

The following code compiles successfully. As per my understanding variables have to be declared before using them then what exactly is happening here

class A {
static {
    y=20;
    z=10;
}
static int z;
static int y=30;
{
    w=10;
}
int w;
public static void main(String args[]){
     System.out.println(y);
}
}

Modified the question after reading the comments. Here the output is 30. So variable declaration happens first, then all the initialization statements are executed as per order of appearance

Upvotes: 0

Views: 67

Answers (2)

Sweeper
Sweeper

Reputation: 274443

variables have to be declared before using them

This is only partially right. If you are in a method and you do this:

System.out.println(i);
int i = 0;

Obviously it won't compile.

But when you are declaring a variable at class level, this rule does no hold. In your code, just because w's declaration is written a few lines after it is being used (w = 10;), it does not mean that the line int w; is executed after the line w = 10;.

Think of it like this: the compiler will see all the static fields' declarations (class level variables) first, then all the non-static fields', then the code blocks (constructors, methods etc) in the class. In your code:

class A {
    static {
        z=10;
    }
    static int z;
    {
        w=10;
    }
    int w;
}

the compiler sees z first, then w. Then let's suppose you access A for the first time in some other parts of your code. Now the static block is executed (z=10;). Let's suppose again that you are actually creating a new instance of A, now w=10; will get executed.

Upvotes: 1

Amer Qarabsa
Amer Qarabsa

Reputation: 6574

Variables are declared by the classloader when it loads the class.

Static block will be evaluated first time the class is accessed so in that time the member variables will be declared, so the order does not really matter

Upvotes: 1

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