Question

I can’t find any example where wildcards can’t be replaced by a generic.
For example:

 public void dummy(List<? extends MyObject> list);

is equivalent to

 public <T> void dummy(List<T extends MyObject> list);

or

 public <T> List<? extends T> dummy2(List<? extends T> list);

is equivalent to

 public <T, U>  List<U extends T> dummy(List<U extends T> list);

So I don’t undertand why wildcard was created as generics is already doing the job. Any ideas or comments?

Answer 1

Nope, it is not always replaceable.

List<? extends Reader> foo();

is not equivalent to

<T> List<T extends Reader> foo();

because you don’t know the T when calling foo() (and you cannot know what List<T> will foo() return. The same thing happens in your second example, too.

The demonstration of using wildcards can be found in this (my) answer.