Jabba vs RVM

Jabba is a free Java version manager written in Go for installing and switching among JDK versions on macOS, Linux and Windows. Its JDK index, powered by DiscoAPI, lists versions for the user's operating system and architecture. The README names distributions including Oracle, Adopt OpenJDK, Zulu, IBM SDK, GraalVM, OpenJDK, Liberica and Amazon Corretto. Users can list remote JDKs, filter versions with semantic version ranges, install versions and switch among those installed. A `.jabbarc` file can specify a project's JDK, while a default alias can select the version used in new terminals. Jabba can link to a system JDK and coexist with an existing Java installation. The README documents shell integration for bash, zsh and fish, plus installation through Homebrew, shell scripts, PowerShell, Scoop or Docker. Custom JDK downloads are also supported. Jabba does not switch Java globally on its own; the README gives manual platform-specific snippets instead. The repository describes Jabba as a community fork that is a work in progress and warns that some README instructions may be outdated. It is licensed under Apache-2.0.

RVM is a command-line tool for installing and managing Ruby versions and gem sets. It can create a self-contained environment for each project, with a selected Ruby version and the gems that project needs. Named gemsets organize gems across Ruby versions, and a shared cache stores one on-disk copy of each downloaded gem. RVM can run test suites, rake tasks, benchmarks, and gem commands against multiple Ruby versions at the same time, supporting consistent setups across development, CI, QA, staging, and production. Its commands cover installing, selecting, upgrading, reinstalling, uninstalling, and removing Ruby versions. Documented integrations include Bundler, Capistrano, Chef, Jenkins, Heroku, and Passenger. RVM supports most UNIX-like systems and Windows through Cygwin or Bash on Ubuntu on Windows. Basic installation needs Bash, curl, gpg2, and GNU tools; git is needed for head Ruby versions. It documents single-user, multi-user, and mixed-mode installs, and recommends single-user mode for an isolated home-directory setup. RVM is free and maintained by community volunteers.