java generics covariance
- by soocracy42
I am having trouble understanding the following article:
http://www.ibm.com/developerworks/java/library/j-jtp01255.html
Under,
Generics are not covariant
the author states,
Because ln is a List, adding a
Float to it seems perfectly legal. But
if ln were aliased with li, then it
would break the type-safety promise
implicit in the definition of li --
that it is a list of integers, which
is why generic types cannot be
covariant.
I can't understand the part where it says
"if ln were aliased with li". What does the author means by alias?(reference?). The code snippet above the quoted line seems to illustrate WHAT is illegal in java and not WHY. It would be very helpful to me if somebody could explain with an example.
Thanks in advance.
