Overriding with Exception

[Raghu Shree]

Select two methods that correctly override the following method? (Assume that all necessary packages have been imported).

protected int aMethod(int i) throws IOException {...}


A. int aMethod(int i) throws IOException{...}
B. protected int aMethod(int i) throws FileNotFoundException{...}
C. public int aMethod(int i) throws Exception{...}
D. public int aMethod(byte i) throws IOException{...}
E. protected int aMethod(int i) throws IOException,FileNotFoundException{...}

Plz some one explain whats the answer with clean explanantion

[Rahul Bhosale]

Answer is B and E.

Rules for override
1. method signature should be the same
2. argument list should be the same
3. return type should be the same
4. visibiliy cannot be reduced (public to private, protected to default etc)
5. cannot declare new exceptions as long as the new exception is a subclass of originally declared Exception.

A fails because of 4.
C fails because of 5
D fails because of 2.

[Srinivasa Raghavan]

yes Answer is B and E for the reasons mentioned by Raghul

[Kenny Birney]

why not c?

[Raghu Shree]

Any one please,

[Anuj Troy]

hii Kenny

c is wrong bec a overriding method must not throw broader checked exception.
but it can throw narrower exception. "Exception" is the broadest exception so it cant be thrown.

regards
anuj

[Sumit Deshpande]

Because the overriding method can throw only those exceptions thrown by the overridden method or the subset of exceptions thrown by the overridden method. But in option C, the method is throwing Exception (the generic exception). This is contradicting our rule of exception for overriding. Thats why C is wrong.

[Raghu Shree]

Some legal overridden methods without exception. for example look at the following code

abstract class MineBase {
abstract void amethod();
static int i;
}
public class Mine extends MineBase {
public static void main(String argv[]){
int[] ar=new int[5];
for(i=0;i < ar.length;i++)
System.out.println(ar[i]);
}
      private void amethod(){
System.out.println("HI");
}
}

if the abstract method amethod() has default access modifier then you will override the following access modifier
public/protected/deault but private is illegal.
if the abstract method amethod() has protected access modifier then you will override the following access modifier
public/protected/ but default & private is illegal.
if the abstract method amethod() has public access modifier then all other access modifiers are illegal.

[Parameswaran Thangavel]

hi
can i say that


1)the Stronger access restirction we can have is default for package level (assuming the overridding method is default)

2)(the Stronger access restirction we can have is protected for between two packages (assuming the overridding method is protected in different package)

[nitin goswami]

I would like to add something in Rahul's answer :
The method Cant not declare new 'Checked' Exceptions untill and unless the exceptions are subclass of the Declared Exception .But the overriden method can declare new 'Runtime Exception'ex. NullPointerException,ArithmaticException etc.