Problem $2(4$ pts$)$: For the following classes and interfaces, indicate briefly which secret is being hidden $($or will be hidden in case of an interface$),$ and how.

a$)$ java.io$.$Closeable

b$)$ java.lang.Comparable $\backslash (\backslash )$

c$)$ java.util.List

d$)$ java.util.Locale