method overidden problem .....

[dmjpro]

class A
{
void test(int a)
{
System.out.println("Normal .... Class A");
}
}

class B extends A
{
int test(int a)
{
System.out.println("Class B");
}
}

i have this code .. a comiler error comes .... here in class B the method can't be overidden ..... why this happens

i think .. it is due to method signature mismatching or anything else ... plz explain and if possible plz explain me in details method signature .......


any help is most welcome ....

[r035198x]

i have this code .. a comiler error comes .... here in class B the method can't be overidden ..... why this happens

i think .. it is due to method signature mismatching or anything else ... plz explain and if possible plz explain me in details method signature .......


any help is most welcome ....

DJ, if you do get time please read the classes here.

You cannot override on return types except in 1.5 with co-variant return types. In that code you have different return types and one is not a subclass of the other so that won't work.

[dmjpro]

thanx for ur reply .....

but i think tell me ... what is method signature and how it is important in mothod override ....

thanxxxx

[dmjpro]

thanx for ur reply .....

but tell me ... what is method signature and how it is important in mothod override ....

thanxxxx

[r035198x]

thanx for ur reply .....

but tell me ... what is method signature and how it is important in mothod override ....

thanxxxx

signature is a combination of
method name,
method arguments,
types of arguments,
order of types of arguments
and number of arguments.

If two methods have exactly the same of these then the two methods have the same signature.

You can only override a method with one with the same signature and the same or covariant return types.

[dmjpro]

right now i m clear .... but plz tell me one more thing .....


subsignature ....... thanxxx

[r035198x]

right now i m clear .... but plz tell me one more thing .....


subsignature ....... thanxxx

From the JLS

"The signature of a method m1 is a subsignature of the signature of a method m2 if either

• m2 has the same signature as m1, or
• the signature of m1 is the same as the erasure of the signature of m2."

[dmjpro]

would u be more clear ... beacause i also saw the line but not understood .....

thanxxxx

[r035198x]

would u be more clear ... beacause i also saw the line but not understood .....

thanxxxx

Have you done any generics yet, DJ?

[dmjpro]

without doing generics can't it be understood???

[r035198x]

without doing generics can't it be understood???

Unfortunately.
There are not too difficult to understand
Here is a simple tutorial for them.