RFR [8037866] Replace the Fun class in tests with lambdas

[Ivan Gerasimov]

Hello!

Would you please help review the fix, which replaces the auxiliary Fun 
class with the same named functional interface?
The anonymous classes instantiations are replaced with lambdas.

BUGURL: https://bugs.openjdk.java.net/browse/JDK-8037866
WEBREV: http://cr.openjdk.java.net/~igerasim/8037866/0/webrev/

Sincerely yours,
Ivan