Doubt

[sangeetha raj]

Hi All,

I have a doubt in this program

1)Since here class A is abstract , we can't instantiate it ,so line 5 will cause compile time error.. (or)

2)Since line 9 is unreachable , it will cause compile error

Which one will be the answer..Because , in Examlab mock test , they have given option 2 is the answer..Please explain me..

public abstract class A{

     public abstract void start() throws ArithmeticException;


     public static void main(String args[]){

          A a=new A(){ //line 5

               public void start() throws ArithmeticException{

                    System.out.print(1);
                    try{
                         System.out.print(2);
                         throw new ArithmeticException();
                         System.out.print(3);//line 9 unreachable
                    }catch(Exception e){
                         System.out.print(4);
                    }finally{
                         System.out.print(5);
                    }

               }

          };

          a.start();
     }

}

Thanks,
SR

[HENRY: Added Code tags]

[Sahil Ji]

[HENRY: Hijack question deleted]

[Anayonkar Shivalkar]

Hi sangeetha raj,

Please UseCodeTags.

Now, coming to your question, what code does is - it creates an anonymous class which IS-A 'A'.

If you are unaware of what inner-class is, then you should read about it and you'll come to know why there's no compile time error at line 5.

Compiler will give error saying line 9 is unreachable.

Secondly, please use meaningful subject to your question/post. It will give some idea to visitors of the forum.

I hope this helps.

[sangeetha raj]

Hi Anayonkar,

Thanks for the clarification..

[Arvind Darwin]

sangeetha raj wrote:
[code = java]
A a=new A(){ //line 5

public void start() throws ArithmeticException{

System.out.print(1);
try{
System.out.print(2);
throw new ArithmeticException();
System.out.print(3);//line 9 unreachable
}catch(Exception e){
System.out.print(4);
}finally{
System.out.print(5);
}

}

};
[/code]

Thanks,
SR

[HENRY: Added Code tags]

Line 5 is not incorrect because abstract class A is not instantiated here.
Anonymous inner class, which is unnamed, and inherits from A and overrides start().
Since anonymous inner class has overridden the abstract start() method of class A, its no longer abstract and can thus be instantiated.

So option 2 is the correct answer.

Read K&B chapter 8 on Inner classes for more insight.

[Anayonkar Shivalkar]

sangeetha raj wrote:Hi Anayonkar,

Thanks for the clarification..

You are welcome.