Understanding Exception Hierarchy

[A Phatak]

I have a doubt about exceptions

It seems the parent class method throws any child or sibling of RuntimeException, and the child throws RuntimeException this is ok. THe compiler accepts it and even runs the program.
However when parent class method throws any child or sibling of RuntimeException, and the child throws Exception this is not ok

class SubException extends RuntimeException{ }
class SubSubException extends SubException { }

class CC { void doStuff() throws SubException { } }

class CC2 extends CC { void doStuff() throws SubSubException { } }

class CC3 extends CC { void doStuff() throws RuntimeException { } }

class CC4 extends CC { void doStuff(int x) throws Exception { } }

class CC5 extends CC { void doStuff() { } } 

In the above code change RuntimeException to Exception ...
I'm having a hard time understanding this, can anyone explain this rule?

[John Stark]

It seems the parent class method throws any child or sibling of RuntimeException, and the child throws RuntimeException this is ok.

RuntimeException is unchecked. Your child can throw any unchecked exception irrespective of whether the parent throws any exception.

when parent class method throws any child or sibling of RuntimeException, and the child throws Exception this is not ok

Exception is checked. If the child throws a checked exception then this has to be the same or a subclass of the exception thrown by the parent.
John

[swapnil kataria]

In case of overriding child class method can not throws wider exception than parent class method in case of checked exception,
but in case of Runtime exception there i no such restriction,
you are throwing Exception in child class and this dose not come under Runtime
so it will not work

[Javin Paul]

Some time it also good to catch the exception and show some other suitable exception from method, called exception chaining though you need to include original exception as source for more information on stack trace.

[A Phatak]

Thanks for the succint explanation...Found the same in Kathy Sierra book in the grey rectangle ... Wonder how I missed

John Stark wrote:

It seems the parent class method throws any child or sibling of RuntimeException, and the child throws RuntimeException this is ok.

RuntimeException is unchecked. Your child can throw any unchecked exception irrespective of whether the parent throws any exception.

when parent class method throws any child or sibling of RuntimeException, and the child throws Exception this is not ok

Exception is checked. If the child throws a checked exception then this has to be the same or a subclass of the exception thrown by the parent.
John