JRuby is a 100% Java implementation of the Ruby programming language. It is Ruby for the JVM.

JRuby provides a complete set of core "builtin" classes and syntax for the Ruby language, as well as most of the Ruby Standard Libraries. The standard libraries are mostly Ruby's own complement of .rb files, but a few that depend on C language-based extensions have been reimplemented. Some are still missing, but we hope to implement as many as is feasible.

See Differences Between MRI And JRuby for more information on potential incompatibilities between JRuby and the C implementation of Ruby.

JRuby's current core development team consists of:

• Charles Oliver Nutter (Red Hat) aka @headius
• Thomas Enebo (Red Hat) aka @enebo
• Marcin Mielzynski aka @lopex

There are also many past contributors who still help out from time to time:

• Ola Bini
• Nick Sieger
• Hiro Asari
• David Calavera
• Yoko Harada
• Hiroshi Nakamura aka NaHi
• Wayne Meissner
• MenTaLguY
• Bill Dortch
• Many more...check out the JRuby commit logs!

• Articles on JRuby internals
• JRuby's Sporadic Blog
• Charles Oliver Nutter's blog
• Thomas Enebo's blog
• Ola Bini's blog
• Nick Sieger's blog