JRuby

JRuby is an implementation of the Ruby programming language atop the Java Virtual Machine (JVM). By translating or interpreting Ruby code to JVM bytecode, JRuby allows Ruby programs to run on any platform that supports Java. It aims to preserve Ruby's syntax and semantics while providing tight interoperability with Java libraries and tools.

Interoperability and ecosystem: JRuby provides seamless access to Java classes and frameworks. Ruby code can instantiate Java objects, call Java methods, and extend Java classes, while Java code can interact with Ruby objects. JRuby supports standard Ruby packaging tools such as RubyGems and Bundler and is compatible with popular Ruby frameworks like Rails and Sinatra.

History and scope: JRuby began in 2007 as an open-source project led by Charles Nutter and Thomas Enebo at Sun Microsystems, with later stewardship by the JRuby project and its community. Ongoing development has aimed to maintain high compatibility with MRI Ruby and to run a broad range of Ruby libraries and frameworks on the JVM.

Performance and use cases: Because it runs on the JVM, JRuby can leverage the platform's JIT compiler, garbage collection, and native threads, offering real multi-threading support compared with MRI. For web applications, JRuby enables deploying Rails or other Ruby apps in Java environments and often allows using Java libraries for performance or integration reasons. JRuby may have different startup characteristics and performance profiles depending on the workload.