Returns a new CompletionStage that is already completed with the given value and supports only those methods in interface {@link CompletionStage}.
@param value the value @param <U> the type of the value @return the completed CompletionStage
See Implementation
Returns a new CompletionStage that is already completed with the given value and supports only those methods in interface {@link CompletionStage}.
@param value the value @param <U> the type of the value @return the completed CompletionStage