Generic Class and Default constructor

[dmjpro]

hey i m new in Generic Class in java.

look at this code carefully ....

[code=java]
class GenerericClass< T>
{
private T d1,d2;
public GenericClass()
{
d1 =100;
d2 = 200;
}
}
[/code]

another part of my code ....

[code=java]
GenericClass<St ring> c = new GenericClass<St ring>();
//It will flash a compiler error .....
[/code]

So my conclusion is that having a default constructor in GenericClass is meaningless.
Right????

i think experts allof u get my point .....
so plz explain ......

kind regards,
Dmjpro.

[JosAH]

hey i m new in Generic Class in java.

look at this code carefully ....

[code=java]
class GenerericClass< T>
{
private T d1,d2;
public GenericClass()
{
d1 =100;
d2 = 200;
}
}
[/code]

If d1 and d2 are of a generic type T you can't assume that they can contain
numbers (Short, Integer, Long, Float or Double). That code is simply wrong and
has nothing to do with the fact that you assume that in a default constructor,
i.e. it is wrong everywhere in a generic class.

kind regards,

Jos

[r035198x]

hey i m new in Generic Class in java.

look at this code carefully ....

[code=java]
class GenerericClass< T>
{
private T d1,d2;
public GenericClass()
{
d1 =100;
d2 = 200;
}
}
[/code]

another part of my code ....

[code=java]
GenericClass<St ring> c = new GenericClass<St ring>();
//It will flash a compiler error .....
[/code]

So my conclusion is that having a default constructor in GenericClass is meaningless.
Right????

i think experts allof u get my point .....
so plz explain ......

kind regards,
Dmjpro.

DJ, Your GenerericClass won't compile for two reasons.
1.) The "constructo r"'s name is different from the class' name and you hav e
d1 =100;
d2 = 200;
which are not allowed since d1 and d2 are objects of a type T which is incompatible with int.

[dmjpro]

If d1 and d2 are of a generic type T you can't assume that they can contain
numbers (Short, Integer, Long, Float or Double). That code is simply wrong and
has nothing to do with the fact that you assume that in a default constructor,
i.e. it is wrong everywhere in a generic class.

kind regards,

Jos

Yup ... u r right.
Actually wat happens .... without compiling the GenericClass i wrote what was in my mind.
now if i want to add some default values in default constructor in generic class then what to do?
plz suggest.

kind regards,
Dmjpro.

[JosAH]

Yup ... u r right.
Actually wat happens .... without compiling the GenericClass i wrote what was in my mind.
now if i want to add some default values in default constructor in generic class then what to do?
plz suggest.

kind regards,
Dmjpro.

If those defaults have a fixed type then those members aren't generic (as in your
example class). If they *are* generic all you know is that you can set them to
something with the same generic type or null. Those numbers 100 and 200 most
certainly aren't generic. You have to redesign your class.

kind regards,

Jos

[dmjpro]

If those defaults have a fixed type then those members aren't generic (as in your
example class). If they *are* generic all you know is that you can set them to
something with the same generic type or null. Those numbers 100 and 200 most
certainly aren't generic. You have to redesign your class.

kind regards,

Jos

ohh that means i have to believe in default values set by the JVM.
right???

kind regards,
Dmjpro.

[r035198x]

ohh that means i have to believe in default values set by the JVM.
right???

kind regards,
Dmjpro.

I don't see where the JVM comes into this.

[dmjpro]

I don't see where the JVM comes into this.

Nooo . i just say generic solved by the compiler but ultimate job done by JVM.
that's why i telling....

Kind regards,
Dmjpro.

[JosAH]

Nooo . i just say generic solved by the compiler but ultimate job done by JVM.
that's why i telling....

Kind regards,
Dmjpro.

If you want a member variable to be equal to 100 or 200, that particular member
variable can't be part of the generic contract. It simply is a number.

kind regards,

Jos

edit: here's a nice tutorial.