$ java --enable-preview StructuredDemo     (JDK 27)
--- allSuccessfulOrThrow(): results as a List, failures as ExecutionException
results = [price=42, stock=7]
CHECK ok   : join() returns the subtask results in fork order
caught java.util.concurrent.ExecutionException with cause java.lang.IllegalStateException: inventory service is down
CHECK ok   : a failing subtask surfaces as ExecutionException(cause)
--- allSuccessfulOrThrow(Function): join() throws the exception type you choose
caught OrderFailed: order failed: inventory service is down
CHECK ok   : the mapped exception wraps the original failure
--- withTimeout(...): what happens when the scope runs out of time
caught java.util.concurrent.ExecutionException
   cause: java.util.concurrent.StructuredTaskScope$CancelledByTimeoutException
CHECK ok   : a timeout is reported as CancelledByTimeoutException
exit=0