Object Reference Conversion

[Sushma]

Hi all,
Chapter 4 of R&H says, object reference conversion is possible when the conversion is up the hierarcy.
My doubt is, how can a superclass class reference hold a subclass reference???
superclass s = subclass p
Sub class would have additional featues than the superclass right..Wouldn't there be loss of information ???
Thanks in advance.
Regards,
Sushma

[rag mul]

only the information available to the superclass is available in such assignments.
the specialized info which the subclass contains is not accessible.

[Venkat Raman]

Hi sushma,
I think u need to understand the difference between object reference and the object itself. Object reference hold addresses of the actual objects( just like pointers in C++).
The ability of a superclass reference variable to hold a reference to subclass object is enabled so that methods can be written in a generic manner.
For example, take vector class. It has a method add(Object ob)
so that any object can be added to a vector. This is because Object is the superclass of all classes.
No information is actually lost because of this.
Regards,
Venkat.