Loom Evades Exception Handling

[Eric Kolotyluk]

Yes, that subject line is click-bait, but this is not intuitive to me... Am
I just seeing an incomplete implementation of Project Loom, and this will
be resolved in the future?

public class Experiment06 {

    public static void main(String args[]) {
        Context.printHeader(Experiment06.class);

        try {
            getRemoteStrings().forEach(System.out::println);
        } catch (ExperimentException e) {
            e.printStackTrace();
        }
    }

    static Stream<String> getRemoteStrings() throws ExperimentException {

        try (var structuredExecutor = StructuredExecutor.open("Experiment06")) {

            // We want complete results, so we won't tolerate failure.
            var completionHandler = new StructuredExecutor.ShutdownOnFailure();

            var futureResults = IntStream.range(0, 15).mapToObj(item -> {
                try {
                    System.out.printf("item = %d, Thread ID = %s\n",
item, Thread.currentThread());
                    return structuredExecutor.fork(() -> {
                        try {
                            System.out.printf("\ttask = %d, Thread ID
= %s\n", item, Thread.currentThread());
                            return getRemoteString(item, new
URI("https://server1/foobar.com/item"));
                        }
                        catch (Throwable t) {
                            System.out.printf("TASK EXCEPTION
%s\n\t%s\n\n", t.getMessage(), t.getCause());
                            t.printStackTrace();
                            throw t;
                        }
                    }, completionHandler);
                } catch (Throwable t) {
                    System.out.printf("SPAWN EXCEPTION %s\n\t%s\n\n",
t.getMessage(), t.getCause());
                    t.printStackTrace();
                    throw t;
                }
            });
            structuredExecutor.joinUntil(Instant.now().plusSeconds(10));
            completionHandler.throwIfFailed();
            return futureResults.map(Future::resultNow);
        }
        catch  (InterruptedException e) {
            e.printStackTrace();
            throw new ExperimentException(e);
        } catch (ExecutionException e) {
            e.printStackTrace();
            throw new ExperimentException(e);
        } catch (TimeoutException e) {
            e.printStackTrace();
            throw new ExperimentException(e);
        } catch (IllegalStateException e) {
            e.printStackTrace();
            throw new ExperimentException(e);
        }
        catch (Throwable t) {
            t.printStackTrace();
            throw new ExperimentException(t);
        }
    }

    static String getRemoteString(int item, URI from) {
        return "Item %d from %s".formatted(item, from);
    }

    static class ExperimentException extends Exception {
        ExperimentException(Throwable cause) {
            super(cause);
        }
    }
}

where I get

[image: image.png]


(Experiment06.java:50) is

return structuredExecutor.fork(() -> {

(Experiment06.java:34) is

getRemoteStrings().forEach(System.out::println);

Is there some way I can actually find out more from the Exception handling,
or other techniques?

Cheers, Eric