Add missing overrides in multi-reader interfaces.
I was code reviewing changes related to multi-reader collections and I noticed that they're missing a bunch of overrides.
These changes are not technically backwards compatible. I don't know if we're planning on a minor release next. Anyway, I wanted to show the changes even if they can't be merged for a while.
@motlin I was hoping we could do a 11.1 release first, as we will be upgrading to Java 11 for EC 12.0 release. We can keep this on the PR queue.
There is a checkstyle failure in the build that needs to be fixed.
@motlin We can review and merge this one now that we are opening 12.0 for next release.
@motlin any update?
@donraab rebased and fixed the checkstyle violation