How can you pass a List to a method?

Question

I have a servlet that, passed on query params, gets a list of objects from the DAO, turns the list into JSON, and sends it back in the response. Every list is made of object

Answer 1

Why don't just use

private String getListAsJson(List<JsonEnabled> list) { ... }

?

Answer 2

For generic wildcards the keyword extends works for both classes and interfaces:

private String getListAsJson(List<? extends JsonEnabled> list) { ... }

extends has slightly different meaning when used for defining generic bounds - it essentially translates to "is, or extends, or implements".