CODEWITHSUNDEEP
javastatic-blockclassloading
Sridhar Srinivasan
Sridhar Srinivasan

Reputation: 83

Why static block is not executed

As per java doc, static block is executed when the class is initialized.

Could anyone please tell me why static block is not executed when I run below code?

class A {
    static {
        System.out.println("Static Block");
    }
}

public class Main {

    public static void example1() {
        Class<?> class1 = A.class;
        System.out.println(class1);
    }


    public static void example2() {
        try {
            Class<?> class1 = Class.forName("ClassLoading_Interview_Example.ex1.A");
            System.out.println(class1);
        }catch(Exception e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        example1();
    }
}

Upvotes: 8

Views: 2530

Answers (2)

xingbin
xingbin

Reputation: 28289

Referencing A.class will not result in executing A's static initializers, see here

Initialization of a class consists of executing its static initializers and the initializers for static fields (class variables) declared in the class.

And

A class or interface type T will be initialized immediately before the first occurrence of any one of the following:

T is a class and an instance of T is created.

A static method declared by T is invoked.

A static field declared by T is assigned.

A static field declared by T is used and the field is not a constant variable (§4.12.4).

Upvotes: 2

arxakoulini
arxakoulini

Reputation: 733

A class's static initialization normally happens immediately before the first time one of the following events occur:

  • an instance of the class is created,
  • a static method of the class is invoked,
  • a static field of the class is assigned,
  • a non-constant static field is used, or [...]

You are currently not doing any of the above. So, by replacing 

Class<?> class1 = A.class;
System.out.println(class1);

with this for example

A object = new A();

will give you your result.

Upvotes: 5

Related Questions