Why use bounded types?

Question

I'm learning about Generics, but I do not see the appeal of Bounded Types. Consider the following:

Class A and B both extends abstract class Letter, which contains a print() method.

So the following code uses Bounded Types and accepts instances of A and B.

public class LetterGeneric<T extends Letter> {
    public LetterGeneric(T t) {
        t.print();
    }
}

The following code also accepts instances of A and B, but it doesn't use generics.

public class LetterNotGeneric {
    LetterNotGeneric(Letter t) {
        t.print();
    }
}

Is there a reason to use Bounded Types NOT demonstrated in this code? Maybe a performance difference between the two?

The websites I've looked at (1/2 for example) explain how Bounded Types work, but fail to explain the difference between the 2 examples given.

By using generics you can do abstractions. You can read this article [Why Use Generics?](https://docs.oracle.com/javase/tutorial/java/generics/why.html) — Butiri Dan, May 30 '19 at 15:32
Another way of answering this is that given your two examples, you're better off using the non-generic class. Generics are for classes that must accept a type of `Object` (like the Collection classes) but some degree of specialization in use is desirable (like the Collection classes). — markspace, May 30 '19 at 15:34
@NathanHughes I'll certainly look into it. I assume you are referring to *Effective Java edition 3 by Joshua Bloch*? — CJCrafter, May 30 '19 at 15:35
A `LetterGeneric` will only accept `A`s, not `B`s. The non-generic version will accept any kind of letter. The bounded type restricts what kind of letter you can pass to it. — marstran, May 30 '19 at 16:20

0 Answers0