Before discussing about 4 rules to handle exception in overriding method. You should understand concepts of

• Method Overriding
• Exception Handling

Exception handling in override method these are 4 rules where you have to handle exceptions for child class according to given parent class scenarios:

Note : When you face any Java interview and test at least one or two questions surely will ask based on these cases to check you Exception Handling concepts and practical knowledge.

Case 1 : If parent-class method doesn’t declare any exception

1. Child class overriding method can declare no exception in overriding method.

   

2. Child class overriding method can declare unchecked exception in overriding method.

   

3. Child class overriding method can declare strictly no checked exception in overriding method.

   

Case 2 : If parent-class method declares unchecked exception

1. Child class overriding method can declare no exception in overriding method.

   

2. Child class overriding method can declare any number of unchecked exception in overriding method.

   

3. Child class overriding method can declare strictly no checked exception in overriding method.

   

Case 3 : If parent-class method declares checked exception

1. Child class overriding method can declare no exception in overriding method.

   

2. Child class overriding method can declare same checked exception in overriding method.

   

3. Child class overriding method can declare sub-type of checked exception in overriding method.
4. Child class overriding method can declare any number of unchecked exception in overriding method.

Case 4 : If parent-class method declares both checked & unchecked exceptions

1. Child class overriding method can declare no exception in overriding method.

   

2. Child class overriding method can declare same checked exception in overriding method.

   

3. Child class overriding method can declare sub-type of checked exception in overriding method.

   

4. Child class overriding method can declare any number of unchecked exception in overriding method.

   

Conclusions

I have covered all scenarios for exception handling in overriding method:

• If parent-class method doesn’t declare any exception, then child-class overriding-method can declare,
  • 1. No exception or
  • 2. Any number of unchecked exception
  • 3. but strictly no checked exception
• If parent-class method  declare unchecked exception, then child-class overriding-method can declare,
  • 1. No exception or
  • 2. Any number of unchecked exception
  • 3. but strictly no checked exception
• If parent-class method  declare checked exception, then child-class overriding-method can declare,
  • 1. No exception or
  • 2. Same checked exception or
  • 3. Sub-type of checked exception or
  • 4. any number of unchecked exception
• All above conclusion hold true, even if combination of both checked & unchecked exception is declared in parent-class’ method

Know More

To know more about Java Exception Hierarchy, in-built exception , checked exception, unchecked exceptions and solutions. You can learn about Exception Handling in override methods and lots more. You can follow below links:  s

• Java Exception Handling Tutorial
• JDBC : Exception and Warning Handling
• Mockito Exceptions Handling
• Java Built-in Exceptions Solutions
• [Top 50] Exception Handling Interview Questions and Answers