init blocks example

[Vidya sumanasekara]

public class Parent {
	static {
		System.out.println("Staticblock Parent ");
	}
	{ System.out.println("Initblock Parent ");	}
	public Parent() {
		System.out.println("Constructor Parent ");
	}
	static {
		System.out.println("Staticblock Parent 2");
	}
} 
class Child extends Parent {
	static {
		System.out.println("Staticblock Child ");
	}
	{ System.out.println("Initblock Child "); }
	public Child() {
		this("A");
		System.out.println("Constructor Child ");
	}
	public Child(String a){
		System.out.println("Constructor Child " + a);
	}
	public static void main(String args[]) {
		new Child();
	}
	{ System.out.println("Initblock Child 2"); }
}

out put:-
Staticblock Parent
Staticblock Parent 2
Exception in thread "main" java.lang.NoSuchMethodError: main


Help me to understand this output....

[kurt hanni]

You are running Parent class, you dont have a main method in your Parent class

[kurt hanni]

- remove public in Parent class
- make Child class public
- rename file to Child.java
- compile Child.java
- run Child

[Vidya sumanasekara]

kurt hanni wrote:You are running Parent class, you dont have a main method in your Parent class

yes .... Thanks..

Then output:-

Staticblock Parent
Staticblock Parent 2
Staticblock Child
Initblock Parent
Constructor Parent
Initblock Child
Initblock Child 2
Constructor Child A
Constructor Child

Can you explain me....

[Ikpefua Jacob-Obinyan]

Vidya sumanasekara wrote:

kurt hanni wrote:You are running Parent class, you dont have a main method in your Parent class

yes .... Thanks..

Then output:-

Staticblock Parent
Staticblock Parent 2
Staticblock Child
Initblock Parent
Constructor Parent
Initblock Child
Initblock Child 2
Constructor Child A
Constructor Child

Can you explain me....

Hello Vidya, study the following VERY carefully, I hope it helps:

1. INIT BLOCKS EXECUTE IN THE ORDER THEY APPEAR

2. STATIC INIT BLOCKS RUN "ONLY ONCE" WHEN THE CLASS IS "FIRST" LOADED BY THE JVM

3. INSTANCE INIT BLOCKS RUN "EACH TIME" A CLASS IS INSTANTIATED

4. INSTANCE INIT BLOCKS RUN "IMMEDIATELY AFTER" THE CONSTRUCTORS CALL TO super()

With the above explanation you can see that the other of execution is:

1. Static init block
2. Instance init block
3. Constructors
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