Q: `trySuccess` vs `success` about learning-examples HOT 3 CLOSED

In this particular example, you need to have some determinism - nondeterminism cannot be avoided. The FileAlterationListener represents an external event source, which may trigger zero, one or more events. Since the Promise/Future can hold at most a single event, only the first (that is, the quickest) invocation of onFileCreate can complete the promise object p.

If we use success to complete the promise, then if the external event source emits two file creation events, the onFileCreate will be called twice, and one of the success calls will throw an exception.
With our definition of determinism, this is deterministic, but not particularly useful - if we ignore the exception, then the rest of the program that depends on the value in the promise becomes non-deterministic anyway.

If we use trySuccess, one of the calls will similarly not succeed, but an exception will not be thrown. In cases like this, where you cannot avoid determinism, it's sometimes better to just use trySuccess.

from learning-examples.

In this particular example, you need to have some determinism - nondeterminism cannot be avoided. The FileAlterationListener represents an external event source, which may trigger zero, one or more events. Since the Promise/Future can hold at most a single event, only the first (that is, the quickest) invocation of onFileCreate can complete the promise object p.

Good explanation.

If we use success to complete the promise, then if the external event source emits two file creation events, the onFileCreate will be called twice, and one of the success calls will throw an exception. With our definition of determinism, this is deterministic, but not particularly useful - if we ignore the exception, then the rest of the program that depends on the value in the promise becomes non-deterministic anyway.

If we use trySuccess, one of the calls will similarly not succeed, but an exception will not be thrown. In cases like this, where you cannot avoid determinism, it's sometimes better to just use trySuccess.

"where you cannot avoid nondeterminism", nor?

from learning-examples.

Yes, typo - "where you cannot avoid nondeterminism".

from learning-examples.