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https://issues.apache.org/jira/browse/JDO-751?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15153660#comment-15153660
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Renato Garcia commented on JDO-751:
-----------------------------------
{quote}
I still don't get the difference between empty and null. Optional does have a
ofNullable() method, which can be used to set it to null. Otherwise, how do you
set it to be `empty`?
{quote}
You use Optional.empty(). Again, the idea of Optional is to abstract {{null}}
away. In the Optional world there are absolutely no nulls, and no {{null}}
references which would invalidate the whole concept as we talked before. Once
using Optional everything that is non-Optional is automatically assumed to be
non-nullable. You need to pick one approach and delimit this world well.
With this idea in mind, {{Optional.ofNullable()}} is for interoperability with
the non-Optional world because {{null}} is still out there. Also, note that you
are not "setting" {{null}}, because Optional is immutable, so you get back a
reference that represents empty. Equally you don't obtain {{null}} from an
Optional - you have to explicitly convert it back to {{null}}, which you'd only
do when you need to go back to non-Optional world. {{Optional.get}} will never
give you back a {{null}}, it raises an {{NoSuchElementException}}, therefore
the code below will always throw an exception:
{{Optional.ofNullable(null).get() == null}}
So you'd need to do something like:
{{
Optional<?> fooOpt = Optional.ofNullable(null);
boolean expr = (fooOpt.isPresent() ? fooOpt.get() : null) == null;
}}
or
{{Optional.ofNullable(null).orElse(null) == null}}
> Support for Java8 Optional
> --------------------------
>
> Key: JDO-751
> URL: https://issues.apache.org/jira/browse/JDO-751
> Project: JDO
> Issue Type: New Feature
> Components: specification, tck
> Reporter: Andy Jefferson
>
> java.util.Optional provides a feature that is available in other languages.
> Since JDO 3.2 will be for Java8+ then it makes sense to add support for this
> as a "supported persistable type"
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