RFR 8080418 Add Optional.or()

[Paul Sandoz]

Hi,

Please review this change to add a method Optional.or that allows one to better compose optionals:

  http://cr.openjdk.java.net/~psandoz/jdk9/JDK-8080418-optional-or/webrev/

I also took the opportunity to clear up the JavaDoc, it was a little inconsistent and i personally found it harder to read in source code.

—

Separately while we are on the topic of Optional i would be interested in opinions on the following changes:

  http://cr.openjdk.java.net/~psandoz/jdk9/optional-prims-filter-map/webrev/

1) add methods that were missing on the primitive specializations; and

2) add to all variants a mapOrElseGet (otherwise known as a “fold”), which is the equivalent of map(mapper).orElseGet(supplier). That is arguably less mind-bending to use when transforming from Optional<T> to Optional<U>.

Paul.