I opened Pandora's box with 4786867.
Lots of failures, starting at https://travis-ci.org/jruby/jruby/builds/4538705/#L600
Some (most?) of these failures come from 1.9's switch to Symbols as Has keys.
In 1.9, method names are symbols. Should fix most (if not all) of #523.
As of 33a66c0, the failure count is down to one (https://travis-ci.org/jruby/jruby/builds/4543860/#L607), although there may be quite a few specs failing within this example (https://github.com/jruby/jruby/blob/33a66c0/spec/java_integration/types/map_spec.rb#L205-L244).
https://travis-ci.org/jruby/jruby/builds/4562310 indicates that 3310615 is the only remaining failure.
I commented out the last bit and renamed MyHash to ToHashImposter to fix the specs. Too many classes defined with the name MyHash apparently. Fixed in commit 42a26dc