What is the difference between 'CompletionStage' and 'CompletableFuture'

Question

I have seen an example in each of them, but I need to know exactly what is the difference in deep, Because sometimes I think I can use both of them to get the same result, S

Answer 1

A CompletableFuture is a CompletionStage. However, as its name suggests, it is

• completable: It can be completed using complete or completeExceptionally.
• a Future: You can use get method, etc. to get the result.

IMHO, in most APIs, like in your example, you should use CompletionStage, because

• The implementation usually provides the mechanism to complete the stage. You don't need/want to expose methods like complete to the caller.
• The caller is expected to use the returned value in an async manner instead of using blocking calls like get provided by Future.