Generics

[joshua antony]

ArrayList<Circle> a = new ArrayList<Circle>();
ArrayList b = a;
ArrayList<Rectangle> c = (ArrayList<Rectangle>)  b;//here

We do not get ClassCastException at runtime at here because generics is not applicable at runtime. Am I right?
[ October 19, 2006: Message edited by: Barry Gaunt ]

[Petrus Pelser]

You may not get an exception at runtime, but you would not be able call a Circle (Compiler complains) or Rectangle (Runtime exception) specific method on an object in the list.

[Aniket Patil]

ArrayList<Circle> a = new ArrayList<Circle>();
ArrayList b = a;
ArrayList<Rectangle> c = b //Here

Take a look at the change at "Here". It works even without the cast, to ensure compatibility with older versions.

[Sharmila Rishi]

Hi Aniket,
According to your code

 ArrayList<Circle> a = new ArrayList<Circle>();
ArrayList b = a;
ArrayList<Rectangle> c = b //Here
   

what you are implying is

  ArrayList<Rectangle> c= new ArrayList<Circle>();  

how will it compile?
can you please explain.



-Sharmila Rishi.

[Keith Lynn]

Originally posted by Sharmila Rishi:
Hi Aniket,
According to your code

 ArrayList<Circle> a = new ArrayList<Circle>();
ArrayList b = a;
ArrayList<Rectangle> c = b //Here
   

what you are implying is

  ArrayList<Rectangle> c= new ArrayList<Circle>();  

how will it compile?
can you please explain.



-Sharmila Rishi.

The type information is lost when the raw ArrayList reference b is assigned to point to the ArrayList<Circle> created in the first line.

[Sharmila Rishi]

So the result would be

  ArrayList<Rectangle> c= new ArrayList();  

Am i right?
If yes, then can we add elements to the ArrayList..?

What will happen when the elements are read back?

Should we have to type cast it...?



-Sharmila Rishi.