Design Question

[Tomchi Tang]

Problem: A customer can have either Checking A/c or Saving Account. There are some features which are specific to checking account and some features which are specific to Saving account. How should we design this.
I come up with the following design:

Interface Account {
   commonMethods();
   savingAccountMethods();
   checkingAccountMethods();
} 
public abstract class AccountBase implements Account {
    public commonMethods() {
// provide common method implementation
    }     
    
    public savingAccountMethods() throws OperationNotSupportedException {
    throw OperationNotSupportedException();
    }
    
    public checkingAccountMethods() throws OperationNotSupportedException {
    throw OperationNotSupportedException();
    }    
}
public class SavingAccount extends AccountBase {
    public savingAccountMethods() {
    // provide the implementation
    }
}
public class CheckingAccount extends AccountBase {
    public checkingAccountMethods() {
    // provide the implementation
    }
}
Just wondering if this is the right approach or should I have a interface hierarchy like this:
Interface Account {
   commonMethods();
}
Interface CheckingAccount extends Account {
   checkingAccountSpecificMethods()
}
Interface SavingAccount extends Account {
   savingAccountSpecificMethods()
}

Would really like to hear some expert comments
Thanks
Tomchi
[added code tags - Ilja]
[ October 16, 2003: Message edited by: Ilja Preuss ]