Some small code to illustrate a bug in JRuby

bug_test.rb

class BugTest1 < Hash
  
  # Any interface will do
  include Java::JavaLang::Runnable

  def run
    puts "Hello from BugTest1"
  end
end

class OrderHash < Hash
end

class BugTest2 < OrderHash
  
  # Any interface will do
  include Java::JavaLang::Runnable
  
  def run
    puts "Hello from BugTest2"
  end
end

# Works just fine
BugTest1.new

# ClassCastException
BugTest2.new