require 'securerandom'
puts SecureRandom.uuid
# OR
#   direct from command line:  jruby -e "require 'securerandom' ; puts SecureRandom.uuid"
# IRB
#   irb(main):001:0> require 'securerandom'
#   true
#   irb(main):002:0> SecureRandom.uuid
#   "8af55604-db60-4347-bb0a-1e13ac058685"