RFR [15] 8233795: Consider adding a notion of a Value-based class to API Documentation index

[Pavel Rappo]

Hello,

Please review the following (documentation) change for https://bugs.openjdk.java.net/browse/JDK-8233795:

   http://cr.openjdk.java.net/~prappo/8233795/webrev.00/

The detailed explanation can be found in the description in the JBS issue. 

Thanks,
-Pavel