Java8: How to get the internal Type of java.util.Optional class?

I have an object of type: Optional<String> and I would like to know at runtime what is the generic type of Optional - meaning 'String'.

I've tried:

obj.getClass()

but this returns java.util.Optional

then I tried, 

obj.getParameterizedType();

but this doesn't return it has Class<> object.

Any idea??

Jon Skeet
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There's no such thing as an object of type Optional<String>. Type erasure means that there's just Optional at execution time. If you have a field or parameter of type Optional<String>, that information can be retrieved at execution time - but the object itself doesn't know about it.

Basically, there's nothing special about Optional<> here - it has all the same limitations as using List<>... although as it's final, you can't even use any of the workarounds used by things like Guava's TypeToken.

See the Java Generics FAQ on Type Erasure for more details.

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