Modern programming languages require generics

Re:Modern programming languages require generics by cogman10 on Tuesday May 24, 2022 @01:10PM (#31494786)

I didn't add it, but the `get` method comes is an override from the `Supplier`.

For example, if we did something like

    class Foo extends HashMap<Foo, Bar> {
      @Override
      Bar put(Foo f, Bar b) {
        super.put(f, b);
      }
    }

The `Map` signature for `put` is `Object put(Object, Object)` due to erasures. However, because you are extending and specifying the generics, the overriden method ends up reifying the type.

All this is to say that generics end up being a little more than just syntactic sugar.

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Re:Modern programming languages require generics by marginalia_nu on Tuesday May 24, 2022 @01:20PM (#31494920)

If you consider this example:

    class Base<T> {
        T f() { return null; }
    }
    class A<T2> extends Base<T2> {
        @Override
        T2 f() { return null; }
    }
    class B extends Base<Integer> {
        @Override
        Integer f() { return null; }
    }
    class C {
        Integer f() { return null; }
    }

Base has a parameter T which is erased in Base.

A has a parameter T2 which is erased in A.

B because B is not a generic class and nothing is erased from B.

Base has the same shape as A; B has the same shape as C.

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