Static block in Java not executed

java static access-modifiers
Sthita picture Sthita · May 31, 2013 · Viewed 12k times · Source 
class Test {
    public static void main(String arg[]) {    
        System.out.println("**MAIN METHOD");
        System.out.println(Mno.VAL); // SOP(9090);
        System.out.println(Mno.VAL + 100); // SOP(9190);
    }

}

class Mno {
    final static int VAL = 9090;
    static {
        System.out.println("**STATIC BLOCK OF Mno\t: " + VAL);
    }
}

I know that a static block executed when class loaded. But in this case the instance variable inside class Mno is final, because of that the static block is not executing.

Why is that so? And if I would remove the final, would it work fine?

Which memory will be allocated first, the static final variable or the static block?

If due to the final access modifier the class does not get loaded, then how can the variable get memory?

Answer

Marko Topolnik picture Marko Topolnik · May 31, 2013
  1. A static final int field is a compile-time constant and its value is hardcoded into the destination class without a reference to its origin;
  2. therefore your main class does not trigger the loading of the class containing the field;
  3. therefore the static initializer in that class is not executed.

In specific detail, the compiled bytecode corresponds to this:

public static void main(String arg[]){    
    System.out.println("**MAIN METHOD");
    System.out.println(9090)
    System.out.println(9190)
}

As soon as you remove final, it is no longer a compile-time constant and the special behavior described above does not apply. The Mno class is loaded as you expect and its static initializer executes.

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