What happens if I don't specify type parameter of a generic superclass

Asked Apr 11 '19 at 19:50

Active Apr 11 '19 at 19:52

Viewed 32 times

Eclipse complains if I have a subclass that extends a generic super class. So say I have an extension of ArrayList but don't specify the type parameter of ArrayList like so:

public class MyArrayList<T> extends ArrayList {
    ...
}

I see a warning:

ArrayList is a raw type. References to generic type ArrayList should be parameterized

It makes sense that ArrayList would be parameterized with <T>, but what exactly can go wrong here?

edited Apr 11 '19 at 19:52

asked Apr 11 '19 at 19:50

b15

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*why is this only a warning? What can go wrong here?* Those sound like opposite questions. – shmosel Apr 11 '19 at 19:51
1

Every time a programmer uses a generic type without a type parameter, a kitten dies. – Dawood ibn Kareem Apr 11 '19 at 19:53
removed the "why is this only a warning?" as it was more of a side question – b15 Apr 11 '19 at 19:53
1

Same as usual: you break type safety. For example, you might call `add("foo");` from within the class. – shmosel Apr 11 '19 at 19:55

What happens if I don't specify type parameter of a generic superclass

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