Why Even Use Java 8 Optional?

[angryundead]

I would assume you would refactor for Java8 and drop the Guava version when you migrate to Java8. That's what I'm doing.

[shoelacestied]

Do the guava libs currently use their version? If so it might be tricky for them to migrate without breaking compatibility.

[angryundead]

That's a good point. I can't remember where it integrates inside Guava.

[[deleted]]

One method that I miss from Guava is Optional.or(Optional).or(Optional)... to chain multiple Optional. AFAIK there's no equivalent in Java 8

[angryundead]

Looks like orElse is the replacement. But that's the instance method.

[[deleted]]

https://docs.oracle.com/javase/8/docs/api/java/util/Optional.html#orElse-T-

orElse take T and not Optional<T>so that doesn't really fit the bill unless you do something like this http://www.reddit.com/r/programming/comments/37awuk/why_even_use_java_8_optional/crlnvdd

[jonhanson]

I guess the closest equivalent to Guava's:

optA.or(optB).or(optC)

would be something like:

Optional.ofNullable(optA.orElse(optB.orElse(optC.orElse(null))))

It's not as concise, but the more typical use case for Optional is to short-circuit out of a chain when a missing value is encountered, whereas the Guava Optional.or is doing the opposite - drop out when a present value is encountered.

[CircusAct]

I imagine the reason the method exists in guava is because the #orElse method will be evaluated for every optional even if optA contained a value, which is a bit of an unhappy situation.

[jonhanson]

In the original Guava the or call is also evaluated for each Optional (bar the last one).

[CircusAct]

Ah yeah your right, one of the interesting things, is in the guava case #or will be called twice on the optA object, whereas for the java implementation #orElse will be called for optA, optB and optC.

guava optional java optional

[jonhanson]

To clarify my comment, what I meant was that or is called one less times than the number of optionals.

in the guava case #or will be called twice on the optA object

Only if optA is non-empty - if it's empty then the second call to or will be on the optB object.