Override Method Exception

[Sachin Dimble]

Hi Friends..
Is there any specific rule while throwing exception in override method?(i got the error ...exception can not be thrown in override method).

Thanx in Advance!
Sachin Dimble.

[Barry Gaunt]

Are you writing about a compile time error or a runtime error?

An overriding method can only throw a subset of the overridden method's declared checked exceptions or subclasses of those checked exceptions. By subset I mean all of, some of, or none of.

[Amit Sharma]

in overriding method u cant throw any broader checked exception.

[Sachin Dimble]

Thanx Barry!
But why is it so?

Sachin Dimble.

[Arvind Sampath]

An overriding method should throw only a subset/subclass of the checked exceptions declared by the original method.

By declaring the exceptions in the throws clause, you make sure that the calling program will handle those exceptions.

 
   
  public class Parent
  {
     public String fetchInfo() throws IOException
     {
          .....    
     }
  }
 
  public class Child extends Parent
  {
     public String fetchInfo() throws IOException,ClassNotFoundException
     {
          .....    
     }
  }
 
   
 

The above code will not compile. Let us assume that it compiles fine. Now if you assign a Child object to a Parent reference and invode the fetchInfo() method using the Parent reference, the compiler will force you to handle the IOException declared by the Parent class. But, at run time, the fetchInfo() method of the Child class will be called and in all probability the method may throw a ClassNotFoundException (and the caller never handled it). Hence, if the above code was allowed to go scott free by the compiler, the JVM would never attain salvation


Hope I answered you



Arvind

[Sachin Dimble]

Thanx A Ton Arvind!!

Sachin Dimble.