Please explain the output

[indra negi]

Please explain why the output of the following code is : r1 r4 pre b1 b2 r3 r2 hawk

class Bird{

{ System.out.print("b1 ");}

public Bird() {System.out.print("b2 ");}

}


class Raptor extends Bird{

static{System.out.print("r1 ");}

public Raptor(){ System.out.print("r2 ");}

{System.out.print("r3 ");}

static{System.out.print("r4 ");}
}

class Hawk extends Raptor{

public static void main(String[] s){

System.out.print("pre ");
new Hawk();
System.out.print("hawk ");

}
}  

[Akanksha Mittal]

Sorry I was wrong here.

[Akanksha Mittal]

So, the order of execution is like this

1. Static initialization blocks
2. Initialization blocks
3. Constructors

I was wrong in the first place.. Thanks for your question..

[Jaydeep Mazumdar]

The output "r1 r4 pre b1 b2 r3 r2 hawk" is described below:

1. Class Hawk and all its parent classes are loaded into memory. As soon as it loads up all static initialization blocks are executed. This explains "r1" and "r4".
2. The main method is executed next. This prints "pre".
3. You create an instance of Hawk. As Hawk extends from Raptor and Raptor from Bird, the Hawk constructor needs to initialize both Bird and Raptor in the same order. This prints "b1" "b2" "r3" and "r4".
4. Finally, the last statement in main is executed. This prints "hawk".


Hope this helps! Any queries, get back to me.

[indra negi]

Thanks Jaydeep and Akanksha.

I was confused about the order of "pre" rest for rest I was sure for their occurence in the output.