overriding question

[Bob CHOI]

/*

compiling code below was successful, i had thought the method overriding by B.doo() would fail without the declaration "throws Exception".

What's the overriding rule regarding it?

Thanks!

*/


class A {

void doo() throws Exception {}

}

class B extends A {

void doo() {}

}

[Joe San]

Hi Bob,

When you override a method, make sure for 2 things regarding exceptions, is that your overriden method cannot throw broader checked exception and if it dosn't throw any checked exceptions also it works. It can throw any run time exceptions.

[Bob CHOI]

just found the rule:

overriding method may throw fewer or narrower checked exceptions, or any unchecked exceptions.

[Bob CHOI]

Thanks, Jothi!

[Suguna Gollapally]

Try the following cod eyou will get error

class A {

void doo() throws Exception {System.out.println("sys");}

}

public class B extends A {

void doo() {System.out.println("sys1");}

public static void main(String s[]) {

A a=new Test();

a.doo();//unreported exception error

Test t=new Test();
t.doo();
}
}

ie Overriding method not declared the exception, declared by the super class

[Suguna Gollapally]

class A {

void doo() throws Exception {System.out.println("sys");}

}

public class Test extends A {

void doo() {System.out.println("sys1");}

public static void main(String s[]) {

A a=new Test();

a.doo();

Test t=new Test();
t.doo();
}
}

[Joe San]

Hi Suguna,

Consider the code below,

public class Main extends Super {
  public String msg= "Sub";
 
void test() {
System.out.println("Sub.test() : " + msg);
}
 
  public static void main (String[] args) throws Exception {
                Super sup1 = new Super();
Main sup2 = new Main();
sup1.test(); //line 1
sup2.test(); //line 2
System.out.println("sup2.msg : " + sup2.msg); //line 3
  }
}
    
class Super {
public String msg= "Super";
 
void test() throws Exception{
System.out.println("Super.test() : " + msg);
}

The above works fine and I'n not saying void test() throws Exception in my subclass. It works just fine. The point is if any method says to the world that it might throw an exception, then callers of that method should make arrangements to handle any exceptional condition that might occur. It has got nothing to do with overriding. Hope you understood the concept.

[Harish Paravasthu]

Hai Jyothi,

Thanks for your deatiled answer... so you say compiler wont check whether the overriding method throws exception or not,but when we call the overridden method,programmer should handle it as it throws checked exception other wise it would be an unreported exception and compiler spit an error...am rite?

Harish