Scjp subclass throwing IOException

Question

class A {
             public void process() { System.out.print("A,"); }
         }
public class B extends A
         {
             public void process() throws IOException  {   //LINE 23
             super.process();
             System.out.print("B,");
             throw new IOException();
          }

 public static void main(String[] args) {

 try { new B().process(); }

 catch (IOException e) { System.out.println("Exception"); }
 }
}

This question is from SCJP 6 , book says that compilation will fail due to an error at Line 23. But what i learned is , you can't throw broader exception when you overide method from parent class. In this Example my parent class method throws no exception , and my ovridden method throws IOException which is subclass of Exception. Then why its not working?

Moreover , i am considering that if my parent class method throws no exception , its by default considered as (( public void process() throws Exception. )) . Is that True??

Answer 1

Your understanding is not correct

public void process(){}

and

public void process() throws Exception{}

are not equivalent. what you can say is equivalent is:

public void process() throws RuntimeException{}

by definition you can not throw a broader exception from a overridden method in subclass. but you can always throw an unchecked exception from any method.

For better understanding please read