Returns a new CompletableFuture that is asynchronously completed
by a task running in the given executor with the value obtained
by calling the given Supplier.
@param supplier a function returning the value to be used
to complete the returned CompletableFuture
@param executor the executor to use for asynchronous execution
@param <U> the function's return type
@return the new CompletableFuture
Returns a new CompletableFuture that is asynchronously completed by a task running in the given executor with the value obtained by calling the given Supplier.
@param supplier a function returning the value to be used to complete the returned CompletableFuture @param executor the executor to use for asynchronous execution @param <U> the function's return type @return the new CompletableFuture