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Adding String to an Integer ArrayList

Vivek Kr Singh
Ranch Hand

Joined: Oct 12, 2007
Posts: 56

Why there is no error on line 20 at runtime?

SCJP 1.4
Ernest Friedman-Hill
author and iconoclast

Joined: Jul 08, 2003
Posts: 24184

With generics, no type checking is done at runtime; they're just a compile-time thing. By passing your List<Integer> to a method accepting just List as an argument, you've completely defeated the type system.

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Rob Spoor

Joined: Oct 27, 2005
Posts: 19693

But the compiler should have given you a warning that you are using a so-called raw type. Whenever you ignore or suppress these warnings, the compiler simply puts all responsibilities on the programmer.

Your example is just waiting for a ClassCastException to happen once you really start using the List, and it all stems from ignoring the warning.

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subject: Adding String to an Integer ArrayList