Generics Question

Basket b = new Basket(); // 1

Basket<Apple> bA = b; // 2

Basket<Orange> bO = b; // 3

bA.setElement(new Apple()); // 4

Orange orange = bO.getElement(); // 5

a)The lines 2 and 3 will cause a compile error.

b)The line 4 will cause a compile error.

c)The line 5 will cause a compile error because a cast is missing.

d)The source code will be compiled with warning(s). During the runtime a ClassCastException will be thrown in the line 5.

e)The soure code will be compiled with warning(s). No exception will be thrown during the runtime.

Source: Java Beat

Please guide me to understand this question!


Regards,
cmbhatt

My two questions (generics) are left orphaned, nobody cares to answer!

Isn't it like Sun has removed the generics from exam ***


Regards,

cmbhatt

***Don't panic please, it is nothing like that. I was eagerly waiting for the answer.

You code is just like the code above. The code compile with warning and will get runtime exception java.lang.ClassCastException on line 5.
[ April 11, 2007: Message edited by: Sam Sunamin ]

I would say option 5.

Consider these test classes.











In line 1, you create a new instance of a Basket but all type information is erased because you created a raw Basket.

In line 2, you cause a compile-time warning to be generated because you are assigning a type safe reference equal to a raw reference.

You also do the same thing in line 3.

Line 4 is fine because bA has reference type Basket<Apple> so you can add an instance of an Apple to it.

But in line 5, the getElement method called on the reference type Basket<Orange> tries to cast the element in the Basket, which is of type Apple, to an Orange.

So you get a ClassCastException.

Thanks Keith,
And for you! specially for making me clear on the Line 5 issue!
I got why runtime "ClassCastException" there!



Regards,
cmbhatt